Merge git://git.infradead.org/~dwmw2/khdrs-2.6

[pandora-kernel.git] / include / linux / fs.h

#ifndef _LINUX_FS_H
#define _LINUX_FS_H

/*
 * This file has definitions for some important file table
 * structures etc.
 */

#include <linux/limits.h>
#include <linux/ioctl.h>

/*
 * It's silly to have NR_OPEN bigger than NR_FILE, but you can change
 * the file limit at runtime and only root can increase the per-process
 * nr_file rlimit, so it's safe to set up a ridiculously high absolute
 * upper limit on files-per-process.
 *
 * Some programs (notably those using select()) may have to be 
 * recompiled to take full advantage of the new limits..  
 */

/* Fixed constants first: */
#undef NR_OPEN
#define NR_OPEN (1024*1024)     /* Absolute upper limit on fd num */
#define INR_OPEN 1024           /* Initial setting for nfile rlimits */

#define BLOCK_SIZE_BITS 10
#define BLOCK_SIZE (1<<BLOCK_SIZE_BITS)

#define SEEK_SET        0       /* seek relative to beginning of file */
#define SEEK_CUR        1       /* seek relative to current file position */
#define SEEK_END        2       /* seek relative to end of file */

/* And dynamically-tunable limits and defaults: */
struct files_stat_struct {
        int nr_files;           /* read only */
        int nr_free_files;      /* read only */
        int max_files;          /* tunable */
};
extern struct files_stat_struct files_stat;
extern int get_max_files(void);

struct inodes_stat_t {
        int nr_inodes;
        int nr_unused;
        int dummy[5];
};
extern struct inodes_stat_t inodes_stat;

extern int leases_enable, lease_break_time;

#ifdef CONFIG_DNOTIFY
extern int dir_notify_enable;
#endif

#define NR_FILE  8192   /* this can well be larger on a larger system */

#define MAY_EXEC 1
#define MAY_WRITE 2
#define MAY_READ 4
#define MAY_APPEND 8

#define FMODE_READ 1
#define FMODE_WRITE 2

/* Internal kernel extensions */
#define FMODE_LSEEK     4
#define FMODE_PREAD     8
#define FMODE_PWRITE    FMODE_PREAD     /* These go hand in hand */

/* File is being opened for execution. Primary users of this flag are
   distributed filesystems that can use it to achieve correct ETXTBUSY
   behavior for cross-node execution/opening_for_writing of files */
#define FMODE_EXEC      16

#define RW_MASK         1
#define RWA_MASK        2
#define READ 0
#define WRITE 1
#define READA 2         /* read-ahead  - don't block if no resources */
#define SWRITE 3        /* for ll_rw_block() - wait for buffer lock */
#define SPECIAL 4       /* For non-blockdevice requests in request queue */
#define READ_SYNC       (READ | (1 << BIO_RW_SYNC))
#define WRITE_SYNC      (WRITE | (1 << BIO_RW_SYNC))
#define WRITE_BARRIER   ((1 << BIO_RW) | (1 << BIO_RW_BARRIER))

#define SEL_IN          1
#define SEL_OUT         2
#define SEL_EX          4

/* public flags for file_system_type */
#define FS_REQUIRES_DEV 1 
#define FS_BINARY_MOUNTDATA 2
#define FS_REVAL_DOT    16384   /* Check the paths ".", ".." for staleness */
#define FS_ODD_RENAME   32768   /* Temporary stuff; will go away as soon
                                  * as nfs_rename() will be cleaned up
                                  */
/*
 * These are the fs-independent mount-flags: up to 32 flags are supported
 */
#define MS_RDONLY        1      /* Mount read-only */
#define MS_NOSUID        2      /* Ignore suid and sgid bits */
#define MS_NODEV         4      /* Disallow access to device special files */
#define MS_NOEXEC        8      /* Disallow program execution */
#define MS_SYNCHRONOUS  16      /* Writes are synced at once */
#define MS_REMOUNT      32      /* Alter flags of a mounted FS */
#define MS_MANDLOCK     64      /* Allow mandatory locks on an FS */
#define MS_DIRSYNC      128     /* Directory modifications are synchronous */
#define MS_NOATIME      1024    /* Do not update access times. */
#define MS_NODIRATIME   2048    /* Do not update directory access times */
#define MS_BIND         4096
#define MS_MOVE         8192
#define MS_REC          16384
#define MS_VERBOSE      32768   /* War is peace. Verbosity is silence.
                                   MS_VERBOSE is deprecated. */
#define MS_SILENT       32768
#define MS_POSIXACL     (1<<16) /* VFS does not apply the umask */
#define MS_UNBINDABLE   (1<<17) /* change to unbindable */
#define MS_PRIVATE      (1<<18) /* change to private */
#define MS_SLAVE        (1<<19) /* change to slave */
#define MS_SHARED       (1<<20) /* change to shared */
#define MS_ACTIVE       (1<<30)
#define MS_NOUSER       (1<<31)

/*
 * Superblock flags that can be altered by MS_REMOUNT
 */
#define MS_RMT_MASK     (MS_RDONLY|MS_SYNCHRONOUS|MS_MANDLOCK)

/*
 * Old magic mount flag and mask
 */
#define MS_MGC_VAL 0xC0ED0000
#define MS_MGC_MSK 0xffff0000

/* Inode flags - they have nothing to superblock flags now */

#define S_SYNC          1       /* Writes are synced at once */
#define S_NOATIME       2       /* Do not update access times */
#define S_APPEND        4       /* Append-only file */
#define S_IMMUTABLE     8       /* Immutable file */
#define S_DEAD          16      /* removed, but still open directory */
#define S_NOQUOTA       32      /* Inode is not counted to quota */
#define S_DIRSYNC       64      /* Directory modifications are synchronous */
#define S_NOCMTIME      128     /* Do not update file c/mtime */
#define S_SWAPFILE      256     /* Do not truncate: swapon got its bmaps */
#define S_PRIVATE       512     /* Inode is fs-internal */

/*
 * Note that nosuid etc flags are inode-specific: setting some file-system
 * flags just means all the inodes inherit those flags by default. It might be
 * possible to override it selectively if you really wanted to with some
 * ioctl() that is not currently implemented.
 *
 * Exception: MS_RDONLY is always applied to the entire file system.
 *
 * Unfortunately, it is possible to change a filesystems flags with it mounted
 * with files in use.  This means that all of the inodes will not have their
 * i_flags updated.  Hence, i_flags no longer inherit the superblock mount
 * flags, so these have to be checked separately. -- rmk@arm.uk.linux.org
 */
#define __IS_FLG(inode,flg) ((inode)->i_sb->s_flags & (flg))

#define IS_RDONLY(inode) ((inode)->i_sb->s_flags & MS_RDONLY)
#define IS_SYNC(inode)          (__IS_FLG(inode, MS_SYNCHRONOUS) || \
                                        ((inode)->i_flags & S_SYNC))
#define IS_DIRSYNC(inode)       (__IS_FLG(inode, MS_SYNCHRONOUS|MS_DIRSYNC) || \
                                        ((inode)->i_flags & (S_SYNC|S_DIRSYNC)))
#define IS_MANDLOCK(inode)      __IS_FLG(inode, MS_MANDLOCK)

#define IS_NOQUOTA(inode)       ((inode)->i_flags & S_NOQUOTA)
#define IS_APPEND(inode)        ((inode)->i_flags & S_APPEND)
#define IS_IMMUTABLE(inode)     ((inode)->i_flags & S_IMMUTABLE)
#define IS_POSIXACL(inode)      __IS_FLG(inode, MS_POSIXACL)

#define IS_DEADDIR(inode)       ((inode)->i_flags & S_DEAD)
#define IS_NOCMTIME(inode)      ((inode)->i_flags & S_NOCMTIME)
#define IS_SWAPFILE(inode)      ((inode)->i_flags & S_SWAPFILE)
#define IS_PRIVATE(inode)       ((inode)->i_flags & S_PRIVATE)

/* the read-only stuff doesn't really belong here, but any other place is
   probably as bad and I don't want to create yet another include file. */

#define BLKROSET   _IO(0x12,93) /* set device read-only (0 = read-write) */
#define BLKROGET   _IO(0x12,94) /* get read-only status (0 = read_write) */
#define BLKRRPART  _IO(0x12,95) /* re-read partition table */
#define BLKGETSIZE _IO(0x12,96) /* return device size /512 (long *arg) */
#define BLKFLSBUF  _IO(0x12,97) /* flush buffer cache */
#define BLKRASET   _IO(0x12,98) /* set read ahead for block device */
#define BLKRAGET   _IO(0x12,99) /* get current read ahead setting */
#define BLKFRASET  _IO(0x12,100)/* set filesystem (mm/filemap.c) read-ahead */
#define BLKFRAGET  _IO(0x12,101)/* get filesystem (mm/filemap.c) read-ahead */
#define BLKSECTSET _IO(0x12,102)/* set max sectors per request (ll_rw_blk.c) */
#define BLKSECTGET _IO(0x12,103)/* get max sectors per request (ll_rw_blk.c) */
#define BLKSSZGET  _IO(0x12,104)/* get block device sector size */
#if 0
#define BLKPG      _IO(0x12,105)/* See blkpg.h */

/* Some people are morons.  Do not use sizeof! */

#define BLKELVGET  _IOR(0x12,106,size_t)/* elevator get */
#define BLKELVSET  _IOW(0x12,107,size_t)/* elevator set */
/* This was here just to show that the number is taken -
   probably all these _IO(0x12,*) ioctls should be moved to blkpg.h. */
#endif
/* A jump here: 108-111 have been used for various private purposes. */
#define BLKBSZGET  _IOR(0x12,112,size_t)
#define BLKBSZSET  _IOW(0x12,113,size_t)
#define BLKGETSIZE64 _IOR(0x12,114,size_t)      /* return device size in bytes (u64 *arg) */
#define BLKTRACESETUP _IOWR(0x12,115,struct blk_user_trace_setup)
#define BLKTRACESTART _IO(0x12,116)
#define BLKTRACESTOP _IO(0x12,117)
#define BLKTRACETEARDOWN _IO(0x12,118)

#define BMAP_IOCTL 1            /* obsolete - kept for compatibility */
#define FIBMAP     _IO(0x00,1)  /* bmap access */
#define FIGETBSZ   _IO(0x00,2)  /* get the block size used for bmap */

#define SYNC_FILE_RANGE_WAIT_BEFORE     1
#define SYNC_FILE_RANGE_WRITE           2
#define SYNC_FILE_RANGE_WAIT_AFTER      4

#ifdef __KERNEL__

#include <linux/linkage.h>
#include <linux/wait.h>
#include <linux/types.h>
#include <linux/kdev_t.h>
#include <linux/dcache.h>
#include <linux/stat.h>
#include <linux/cache.h>
#include <linux/kobject.h>
#include <linux/list.h>
#include <linux/radix-tree.h>
#include <linux/prio_tree.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/mutex.h>

#include <asm/atomic.h>
#include <asm/semaphore.h>
#include <asm/byteorder.h>

struct hd_geometry;
struct iovec;
struct nameidata;
struct kiocb;
struct pipe_inode_info;
struct poll_table_struct;
struct kstatfs;
struct vm_area_struct;
struct vfsmount;

extern void __init inode_init(unsigned long);
extern void __init inode_init_early(void);
extern void __init mnt_init(unsigned long);
extern void __init files_init(unsigned long);

struct buffer_head;
typedef int (get_block_t)(struct inode *inode, sector_t iblock,
                        struct buffer_head *bh_result, int create);
typedef void (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
                        ssize_t bytes, void *private);

/*
 * Attribute flags.  These should be or-ed together to figure out what
 * has been changed!
 */
#define ATTR_MODE       1
#define ATTR_UID        2
#define ATTR_GID        4
#define ATTR_SIZE       8
#define ATTR_ATIME      16
#define ATTR_MTIME      32
#define ATTR_CTIME      64
#define ATTR_ATIME_SET  128
#define ATTR_MTIME_SET  256
#define ATTR_FORCE      512     /* Not a change, but a change it */
#define ATTR_ATTR_FLAG  1024
#define ATTR_KILL_SUID  2048
#define ATTR_KILL_SGID  4096
#define ATTR_FILE       8192

/*
 * This is the Inode Attributes structure, used for notify_change().  It
 * uses the above definitions as flags, to know which values have changed.
 * Also, in this manner, a Filesystem can look at only the values it cares
 * about.  Basically, these are the attributes that the VFS layer can
 * request to change from the FS layer.
 *
 * Derek Atkins <warlord@MIT.EDU> 94-10-20
 */
struct iattr {
        unsigned int    ia_valid;
        umode_t         ia_mode;
        uid_t           ia_uid;
        gid_t           ia_gid;
        loff_t          ia_size;
        struct timespec ia_atime;
        struct timespec ia_mtime;
        struct timespec ia_ctime;

        /*
         * Not an attribute, but an auxilary info for filesystems wanting to
         * implement an ftruncate() like method.  NOTE: filesystem should
         * check for (ia_valid & ATTR_FILE), and not for (ia_file != NULL).
         */
        struct file     *ia_file;
};

/*
 * Includes for diskquotas.
 */
#include <linux/quota.h>

/** 
 * enum positive_aop_returns - aop return codes with specific semantics
 *
 * @AOP_WRITEPAGE_ACTIVATE: Informs the caller that page writeback has
 *                          completed, that the page is still locked, and
 *                          should be considered active.  The VM uses this hint
 *                          to return the page to the active list -- it won't
 *                          be a candidate for writeback again in the near
 *                          future.  Other callers must be careful to unlock
 *                          the page if they get this return.  Returned by
 *                          writepage(); 
 *
 * @AOP_TRUNCATED_PAGE: The AOP method that was handed a locked page has
 *                      unlocked it and the page might have been truncated.
 *                      The caller should back up to acquiring a new page and
 *                      trying again.  The aop will be taking reasonable
 *                      precautions not to livelock.  If the caller held a page
 *                      reference, it should drop it before retrying.  Returned
 *                      by readpage(), prepare_write(), and commit_write().
 *
 * address_space_operation functions return these large constants to indicate
 * special semantics to the caller.  These are much larger than the bytes in a
 * page to allow for functions that return the number of bytes operated on in a
 * given page.
 */

enum positive_aop_returns {
        AOP_WRITEPAGE_ACTIVATE  = 0x80000,
        AOP_TRUNCATED_PAGE      = 0x80001,
};

/*
 * oh the beauties of C type declarations.
 */
struct page;
struct address_space;
struct writeback_control;

struct address_space_operations {
        int (*writepage)(struct page *page, struct writeback_control *wbc);
        int (*readpage)(struct file *, struct page *);
        void (*sync_page)(struct page *);

        /* Write back some dirty pages from this mapping. */
        int (*writepages)(struct address_space *, struct writeback_control *);

        /* Set a page dirty.  Return true if this dirtied it */
        int (*set_page_dirty)(struct page *page);

        int (*readpages)(struct file *filp, struct address_space *mapping,
                        struct list_head *pages, unsigned nr_pages);

        /*
         * ext3 requires that a successful prepare_write() call be followed
         * by a commit_write() call - they must be balanced
         */
        int (*prepare_write)(struct file *, struct page *, unsigned, unsigned);
        int (*commit_write)(struct file *, struct page *, unsigned, unsigned);
        /* Unfortunately this kludge is needed for FIBMAP. Don't use it */
        sector_t (*bmap)(struct address_space *, sector_t);
        void (*invalidatepage) (struct page *, unsigned long);
        int (*releasepage) (struct page *, gfp_t);
        ssize_t (*direct_IO)(int, struct kiocb *, const struct iovec *iov,
                        loff_t offset, unsigned long nr_segs);
        struct page* (*get_xip_page)(struct address_space *, sector_t,
                        int);
        /* migrate the contents of a page to the specified target */
        int (*migratepage) (struct address_space *,
                        struct page *, struct page *);
};

struct backing_dev_info;
struct address_space {
        struct inode            *host;          /* owner: inode, block_device */
        struct radix_tree_root  page_tree;      /* radix tree of all pages */
        rwlock_t                tree_lock;      /* and rwlock protecting it */
        unsigned int            i_mmap_writable;/* count VM_SHARED mappings */
        struct prio_tree_root   i_mmap;         /* tree of private and shared mappings */
        struct list_head        i_mmap_nonlinear;/*list VM_NONLINEAR mappings */
        spinlock_t              i_mmap_lock;    /* protect tree, count, list */
        unsigned int            truncate_count; /* Cover race condition with truncate */
        unsigned long           nrpages;        /* number of total pages */
        pgoff_t                 writeback_index;/* writeback starts here */
        const struct address_space_operations *a_ops;   /* methods */
        unsigned long           flags;          /* error bits/gfp mask */
        struct backing_dev_info *backing_dev_info; /* device readahead, etc */
        spinlock_t              private_lock;   /* for use by the address_space */
        struct list_head        private_list;   /* ditto */
        struct address_space    *assoc_mapping; /* ditto */
} __attribute__((aligned(sizeof(long))));
        /*
         * On most architectures that alignment is already the case; but
         * must be enforced here for CRIS, to let the least signficant bit
         * of struct page's "mapping" pointer be used for PAGE_MAPPING_ANON.
         */

struct block_device {
        dev_t                   bd_dev;  /* not a kdev_t - it's a search key */
        struct inode *          bd_inode;       /* will die */
        int                     bd_openers;
        struct mutex            bd_mutex;       /* open/close mutex */
        struct mutex            bd_mount_mutex; /* mount mutex */
        struct list_head        bd_inodes;
        void *                  bd_holder;
        int                     bd_holders;
#ifdef CONFIG_SYSFS
        struct list_head        bd_holder_list;
#endif
        struct block_device *   bd_contains;
        unsigned                bd_block_size;
        struct hd_struct *      bd_part;
        /* number of times partitions within this device have been opened. */
        unsigned                bd_part_count;
        int                     bd_invalidated;
        struct gendisk *        bd_disk;
        struct list_head        bd_list;
        struct backing_dev_info *bd_inode_backing_dev_info;
        /*
         * Private data.  You must have bd_claim'ed the block_device
         * to use this.  NOTE:  bd_claim allows an owner to claim
         * the same device multiple times, the owner must take special
         * care to not mess up bd_private for that case.
         */
        unsigned long           bd_private;
};

/*
 * bdev->bd_mutex nesting subclasses for the lock validator:
 *
 * 0: normal
 * 1: 'whole'
 * 2: 'partition'
 */
enum bdev_bd_mutex_lock_class
{
        BD_MUTEX_NORMAL,
        BD_MUTEX_WHOLE,
        BD_MUTEX_PARTITION
};


/*
 * Radix-tree tags, for tagging dirty and writeback pages within the pagecache
 * radix trees
 */
#define PAGECACHE_TAG_DIRTY     0
#define PAGECACHE_TAG_WRITEBACK 1

int mapping_tagged(struct address_space *mapping, int tag);

/*
 * Might pages of this file be mapped into userspace?
 */
static inline int mapping_mapped(struct address_space *mapping)
{
        return  !prio_tree_empty(&mapping->i_mmap) ||
                !list_empty(&mapping->i_mmap_nonlinear);
}

/*
 * Might pages of this file have been modified in userspace?
 * Note that i_mmap_writable counts all VM_SHARED vmas: do_mmap_pgoff
 * marks vma as VM_SHARED if it is shared, and the file was opened for
 * writing i.e. vma may be mprotected writable even if now readonly.
 */
static inline int mapping_writably_mapped(struct address_space *mapping)
{
        return mapping->i_mmap_writable != 0;
}

/*
 * Use sequence counter to get consistent i_size on 32-bit processors.
 */
#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
#include <linux/seqlock.h>
#define __NEED_I_SIZE_ORDERED
#define i_size_ordered_init(inode) seqcount_init(&inode->i_size_seqcount)
#else
#define i_size_ordered_init(inode) do { } while (0)
#endif

struct inode {
        struct hlist_node       i_hash;
        struct list_head        i_list;
        struct list_head        i_sb_list;
        struct list_head        i_dentry;
        unsigned long           i_ino;
        atomic_t                i_count;
        umode_t                 i_mode;
        unsigned int            i_nlink;
        uid_t                   i_uid;
        gid_t                   i_gid;
        dev_t                   i_rdev;
        loff_t                  i_size;
        struct timespec         i_atime;
        struct timespec         i_mtime;
        struct timespec         i_ctime;
        unsigned int            i_blkbits;
        unsigned long           i_blksize;
        unsigned long           i_version;
        blkcnt_t                i_blocks;
        unsigned short          i_bytes;
        spinlock_t              i_lock; /* i_blocks, i_bytes, maybe i_size */
        struct mutex            i_mutex;
        struct rw_semaphore     i_alloc_sem;
        struct inode_operations *i_op;
        const struct file_operations    *i_fop; /* former ->i_op->default_file_ops */
        struct super_block      *i_sb;
        struct file_lock        *i_flock;
        struct address_space    *i_mapping;
        struct address_space    i_data;
#ifdef CONFIG_QUOTA
        struct dquot            *i_dquot[MAXQUOTAS];
#endif
        /* These three should probably be a union */
        struct list_head        i_devices;
        struct pipe_inode_info  *i_pipe;
        struct block_device     *i_bdev;
        struct cdev             *i_cdev;
        int                     i_cindex;

        __u32                   i_generation;

#ifdef CONFIG_DNOTIFY
        unsigned long           i_dnotify_mask; /* Directory notify events */
        struct dnotify_struct   *i_dnotify; /* for directory notifications */
#endif

#ifdef CONFIG_INOTIFY
        struct list_head        inotify_watches; /* watches on this inode */
        struct mutex            inotify_mutex;  /* protects the watches list */
#endif

        unsigned long           i_state;
        unsigned long           dirtied_when;   /* jiffies of first dirtying */

        unsigned int            i_flags;

        atomic_t                i_writecount;
        void                    *i_security;
        union {
                void            *generic_ip;
        } u;
#ifdef __NEED_I_SIZE_ORDERED
        seqcount_t              i_size_seqcount;
#endif
};

/*
 * inode->i_mutex nesting subclasses for the lock validator:
 *
 * 0: the object of the current VFS operation
 * 1: parent
 * 2: child/target
 * 3: quota file
 *
 * The locking order between these classes is
 * parent -> child -> normal -> xattr -> quota
 */
enum inode_i_mutex_lock_class
{
        I_MUTEX_NORMAL,
        I_MUTEX_PARENT,
        I_MUTEX_CHILD,
        I_MUTEX_XATTR,
        I_MUTEX_QUOTA
};

/*
 * NOTE: in a 32bit arch with a preemptable kernel and
 * an UP compile the i_size_read/write must be atomic
 * with respect to the local cpu (unlike with preempt disabled),
 * but they don't need to be atomic with respect to other cpus like in
 * true SMP (so they need either to either locally disable irq around
 * the read or for example on x86 they can be still implemented as a
 * cmpxchg8b without the need of the lock prefix). For SMP compiles
 * and 64bit archs it makes no difference if preempt is enabled or not.
 */
static inline loff_t i_size_read(struct inode *inode)
{
#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
        loff_t i_size;
        unsigned int seq;

        do {
                seq = read_seqcount_begin(&inode->i_size_seqcount);
                i_size = inode->i_size;
        } while (read_seqcount_retry(&inode->i_size_seqcount, seq));
        return i_size;
#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPT)
        loff_t i_size;

        preempt_disable();
        i_size = inode->i_size;
        preempt_enable();
        return i_size;
#else
        return inode->i_size;
#endif
}


static inline void i_size_write(struct inode *inode, loff_t i_size)
{
#if BITS_PER_LONG==32 && defined(CONFIG_SMP)
        write_seqcount_begin(&inode->i_size_seqcount);
        inode->i_size = i_size;
        write_seqcount_end(&inode->i_size_seqcount);
#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPT)
        preempt_disable();
        inode->i_size = i_size;
        preempt_enable();
#else
        inode->i_size = i_size;
#endif
}

static inline unsigned iminor(struct inode *inode)
{
        return MINOR(inode->i_rdev);
}

static inline unsigned imajor(struct inode *inode)
{
        return MAJOR(inode->i_rdev);
}

extern struct block_device *I_BDEV(struct inode *inode);

struct fown_struct {
        rwlock_t lock;          /* protects pid, uid, euid fields */
        int pid;                /* pid or -pgrp where SIGIO should be sent */
        uid_t uid, euid;        /* uid/euid of process setting the owner */
        void *security;
        int signum;             /* posix.1b rt signal to be delivered on IO */
};

/*
 * Track a single file's readahead state
 */
struct file_ra_state {
        unsigned long start;            /* Current window */
        unsigned long size;
        unsigned long flags;            /* ra flags RA_FLAG_xxx*/
        unsigned long cache_hit;        /* cache hit count*/
        unsigned long prev_page;        /* Cache last read() position */
        unsigned long ahead_start;      /* Ahead window */
        unsigned long ahead_size;
        unsigned long ra_pages;         /* Maximum readahead window */
        unsigned long mmap_hit;         /* Cache hit stat for mmap accesses */
        unsigned long mmap_miss;        /* Cache miss stat for mmap accesses */
};
#define RA_FLAG_MISS 0x01       /* a cache miss occured against this file */
#define RA_FLAG_INCACHE 0x02    /* file is already in cache */

struct file {
        /*
         * fu_list becomes invalid after file_free is called and queued via
         * fu_rcuhead for RCU freeing
         */
        union {
                struct list_head        fu_list;
                struct rcu_head         fu_rcuhead;
        } f_u;
        struct dentry           *f_dentry;
        struct vfsmount         *f_vfsmnt;
        const struct file_operations    *f_op;
        atomic_t                f_count;
        unsigned int            f_flags;
        mode_t                  f_mode;
        loff_t                  f_pos;
        struct fown_struct      f_owner;
        unsigned int            f_uid, f_gid;
        struct file_ra_state    f_ra;

        unsigned long           f_version;
        void                    *f_security;

        /* needed for tty driver, and maybe others */
        void                    *private_data;

#ifdef CONFIG_EPOLL
        /* Used by fs/eventpoll.c to link all the hooks to this file */
        struct list_head        f_ep_links;
        spinlock_t              f_ep_lock;
#endif /* #ifdef CONFIG_EPOLL */
        struct address_space    *f_mapping;
};
extern spinlock_t files_lock;
#define file_list_lock() spin_lock(&files_lock);
#define file_list_unlock() spin_unlock(&files_lock);

#define get_file(x)     atomic_inc(&(x)->f_count)
#define file_count(x)   atomic_read(&(x)->f_count)

#define MAX_NON_LFS     ((1UL<<31) - 1)

/* Page cache limit. The filesystems should put that into their s_maxbytes 
   limits, otherwise bad things can happen in VM. */ 
#if BITS_PER_LONG==32
#define MAX_LFS_FILESIZE        (((u64)PAGE_CACHE_SIZE << (BITS_PER_LONG-1))-1) 
#elif BITS_PER_LONG==64
#define MAX_LFS_FILESIZE        0x7fffffffffffffffUL
#endif

#define FL_POSIX        1
#define FL_FLOCK        2
#define FL_ACCESS       8       /* not trying to lock, just looking */
#define FL_EXISTS       16      /* when unlocking, test for existence */
#define FL_LEASE        32      /* lease held on this file */
#define FL_CLOSE        64      /* unlock on close */
#define FL_SLEEP        128     /* A blocking lock */

/*
 * The POSIX file lock owner is determined by
 * the "struct files_struct" in the thread group
 * (or NULL for no owner - BSD locks).
 *
 * Lockd stuffs a "host" pointer into this.
 */
typedef struct files_struct *fl_owner_t;

struct file_lock_operations {
        void (*fl_insert)(struct file_lock *);  /* lock insertion callback */
        void (*fl_remove)(struct file_lock *);  /* lock removal callback */
        void (*fl_copy_lock)(struct file_lock *, struct file_lock *);
        void (*fl_release_private)(struct file_lock *);
};

struct lock_manager_operations {
        int (*fl_compare_owner)(struct file_lock *, struct file_lock *);
        void (*fl_notify)(struct file_lock *);  /* unblock callback */
        void (*fl_copy_lock)(struct file_lock *, struct file_lock *);
        void (*fl_release_private)(struct file_lock *);
        void (*fl_break)(struct file_lock *);
        int (*fl_mylease)(struct file_lock *, struct file_lock *);
        int (*fl_change)(struct file_lock **, int);
};

/* that will die - we need it for nfs_lock_info */
#include <linux/nfs_fs_i.h>

struct file_lock {
        struct file_lock *fl_next;      /* singly linked list for this inode  */
        struct list_head fl_link;       /* doubly linked list of all locks */
        struct list_head fl_block;      /* circular list of blocked processes */
        fl_owner_t fl_owner;
        unsigned int fl_pid;
        wait_queue_head_t fl_wait;
        struct file *fl_file;
        unsigned char fl_flags;
        unsigned char fl_type;
        loff_t fl_start;
        loff_t fl_end;

        struct fasync_struct *  fl_fasync; /* for lease break notifications */
        unsigned long fl_break_time;    /* for nonblocking lease breaks */

        struct file_lock_operations *fl_ops;    /* Callbacks for filesystems */
        struct lock_manager_operations *fl_lmops;       /* Callbacks for lockmanagers */
        union {
                struct nfs_lock_info    nfs_fl;
                struct nfs4_lock_info   nfs4_fl;
        } fl_u;
};

/* The following constant reflects the upper bound of the file/locking space */
#ifndef OFFSET_MAX
#define INT_LIMIT(x)    (~((x)1 << (sizeof(x)*8 - 1)))
#define OFFSET_MAX      INT_LIMIT(loff_t)
#define OFFT_OFFSET_MAX INT_LIMIT(off_t)
#endif

#include <linux/fcntl.h>

extern int fcntl_getlk(struct file *, struct flock __user *);
extern int fcntl_setlk(unsigned int, struct file *, unsigned int,
                        struct flock __user *);

#if BITS_PER_LONG == 32
extern int fcntl_getlk64(struct file *, struct flock64 __user *);
extern int fcntl_setlk64(unsigned int, struct file *, unsigned int,
                        struct flock64 __user *);
#endif

extern void send_sigio(struct fown_struct *fown, int fd, int band);
extern int fcntl_setlease(unsigned int fd, struct file *filp, long arg);
extern int fcntl_getlease(struct file *filp);

/* fs/sync.c */
extern int do_sync_file_range(struct file *file, loff_t offset, loff_t endbyte,
                        unsigned int flags);

/* fs/locks.c */
extern void locks_init_lock(struct file_lock *);
extern void locks_copy_lock(struct file_lock *, struct file_lock *);
extern void locks_remove_posix(struct file *, fl_owner_t);
extern void locks_remove_flock(struct file *);
extern int posix_test_lock(struct file *, struct file_lock *, struct file_lock *);
extern int posix_lock_file_conf(struct file *, struct file_lock *, struct file_lock *);
extern int posix_lock_file(struct file *, struct file_lock *);
extern int posix_lock_file_wait(struct file *, struct file_lock *);
extern int posix_unblock_lock(struct file *, struct file_lock *);
extern int flock_lock_file_wait(struct file *filp, struct file_lock *fl);
extern int __break_lease(struct inode *inode, unsigned int flags);
extern void lease_get_mtime(struct inode *, struct timespec *time);
extern int setlease(struct file *, long, struct file_lock **);
extern int lease_modify(struct file_lock **, int);
extern int lock_may_read(struct inode *, loff_t start, unsigned long count);
extern int lock_may_write(struct inode *, loff_t start, unsigned long count);

struct fasync_struct {
        int     magic;
        int     fa_fd;
        struct  fasync_struct   *fa_next; /* singly linked list */
        struct  file            *fa_file;
};

#define FASYNC_MAGIC 0x4601

/* SMP safe fasync helpers: */
extern int fasync_helper(int, struct file *, int, struct fasync_struct **);
/* can be called from interrupts */
extern void kill_fasync(struct fasync_struct **, int, int);
/* only for net: no internal synchronization */
extern void __kill_fasync(struct fasync_struct *, int, int);

extern int f_setown(struct file *filp, unsigned long arg, int force);
extern void f_delown(struct file *filp);
extern int send_sigurg(struct fown_struct *fown);

/*
 *      Umount options
 */

#define MNT_FORCE       0x00000001      /* Attempt to forcibily umount */
#define MNT_DETACH      0x00000002      /* Just detach from the tree */
#define MNT_EXPIRE      0x00000004      /* Mark for expiry */

extern struct list_head super_blocks;
extern spinlock_t sb_lock;

#define sb_entry(list)  list_entry((list), struct super_block, s_list)
#define S_BIAS (1<<30)
struct super_block {
        struct list_head        s_list;         /* Keep this first */
        dev_t                   s_dev;          /* search index; _not_ kdev_t */
        unsigned long           s_blocksize;
        unsigned char           s_blocksize_bits;
        unsigned char           s_dirt;
        unsigned long long      s_maxbytes;     /* Max file size */
        struct file_system_type *s_type;
        struct super_operations *s_op;
        struct dquot_operations *dq_op;
        struct quotactl_ops     *s_qcop;
        struct export_operations *s_export_op;
        unsigned long           s_flags;
        unsigned long           s_magic;
        struct dentry           *s_root;
        struct rw_semaphore     s_umount;
        struct mutex            s_lock;
        int                     s_count;
        int                     s_syncing;
        int                     s_need_sync_fs;
        atomic_t                s_active;
        void                    *s_security;
        struct xattr_handler    **s_xattr;

        struct list_head        s_inodes;       /* all inodes */
        struct list_head        s_dirty;        /* dirty inodes */
        struct list_head        s_io;           /* parked for writeback */
        struct hlist_head       s_anon;         /* anonymous dentries for (nfs) exporting */
        struct list_head        s_files;

        struct block_device     *s_bdev;
        struct list_head        s_instances;
        struct quota_info       s_dquot;        /* Diskquota specific options */

        int                     s_frozen;
        wait_queue_head_t       s_wait_unfrozen;

        char s_id[32];                          /* Informational name */

        void                    *s_fs_info;     /* Filesystem private info */

        /*
         * The next field is for VFS *only*. No filesystems have any business
         * even looking at it. You had been warned.
         */
        struct mutex s_vfs_rename_mutex;        /* Kludge */

        /* Granularity of c/m/atime in ns.
           Cannot be worse than a second */
        u32                s_time_gran;
};

extern struct timespec current_fs_time(struct super_block *sb);

/*
 * Snapshotting support.
 */
enum {
        SB_UNFROZEN = 0,
        SB_FREEZE_WRITE = 1,
        SB_FREEZE_TRANS = 2,
};

#define vfs_check_frozen(sb, level) \
        wait_event((sb)->s_wait_unfrozen, ((sb)->s_frozen < (level)))

static inline void get_fs_excl(void)
{
        atomic_inc(&current->fs_excl);
}

static inline void put_fs_excl(void)
{
        atomic_dec(&current->fs_excl);
}

static inline int has_fs_excl(void)
{
        return atomic_read(&current->fs_excl);
}


/*
 * Superblock locking.
 */
static inline void lock_super(struct super_block * sb)
{
        get_fs_excl();
        mutex_lock(&sb->s_lock);
}

static inline void unlock_super(struct super_block * sb)
{
        put_fs_excl();
        mutex_unlock(&sb->s_lock);
}

/*
 * VFS helper functions..
 */
extern int vfs_permission(struct nameidata *, int);
extern int vfs_create(struct inode *, struct dentry *, int, struct nameidata *);
extern int vfs_mkdir(struct inode *, struct dentry *, int);
extern int vfs_mknod(struct inode *, struct dentry *, int, dev_t);
extern int vfs_symlink(struct inode *, struct dentry *, const char *, int);
extern int vfs_link(struct dentry *, struct inode *, struct dentry *);
extern int vfs_rmdir(struct inode *, struct dentry *);
extern int vfs_unlink(struct inode *, struct dentry *);
extern int vfs_rename(struct inode *, struct dentry *, struct inode *, struct dentry *);

/*
 * VFS dentry helper functions.
 */
extern void dentry_unhash(struct dentry *dentry);

/*
 * VFS file helper functions.
 */
extern int file_permission(struct file *, int);

/*
 * File types
 *
 * NOTE! These match bits 12..15 of stat.st_mode
 * (ie "(i_mode >> 12) & 15").
 */
#define DT_UNKNOWN      0
#define DT_FIFO         1
#define DT_CHR          2
#define DT_DIR          4
#define DT_BLK          6
#define DT_REG          8
#define DT_LNK          10
#define DT_SOCK         12
#define DT_WHT          14

#define OSYNC_METADATA  (1<<0)
#define OSYNC_DATA      (1<<1)
#define OSYNC_INODE     (1<<2)
int generic_osync_inode(struct inode *, struct address_space *, int);

/*
 * This is the "filldir" function type, used by readdir() to let
 * the kernel specify what kind of dirent layout it wants to have.
 * This allows the kernel to read directories into kernel space or
 * to have different dirent layouts depending on the binary type.
 */
typedef int (*filldir_t)(void *, const char *, int, loff_t, ino_t, unsigned);

struct block_device_operations {
        int (*open) (struct inode *, struct file *);
        int (*release) (struct inode *, struct file *);
        int (*ioctl) (struct inode *, struct file *, unsigned, unsigned long);
        long (*unlocked_ioctl) (struct file *, unsigned, unsigned long);
        long (*compat_ioctl) (struct file *, unsigned, unsigned long);
        int (*direct_access) (struct block_device *, sector_t, unsigned long *);
        int (*media_changed) (struct gendisk *);
        int (*revalidate_disk) (struct gendisk *);
        int (*getgeo)(struct block_device *, struct hd_geometry *);
        struct module *owner;
};

/*
 * "descriptor" for what we're up to with a read for sendfile().
 * This allows us to use the same read code yet
 * have multiple different users of the data that
 * we read from a file.
 *
 * The simplest case just copies the data to user
 * mode.
 */
typedef struct {
        size_t written;
        size_t count;
        union {
                char __user * buf;
                void *data;
        } arg;
        int error;
} read_descriptor_t;

typedef int (*read_actor_t)(read_descriptor_t *, struct page *, unsigned long, unsigned long);

/* These macros are for out of kernel modules to test that
 * the kernel supports the unlocked_ioctl and compat_ioctl
 * fields in struct file_operations. */
#define HAVE_COMPAT_IOCTL 1
#define HAVE_UNLOCKED_IOCTL 1

/*
 * NOTE:
 * read, write, poll, fsync, readv, writev, unlocked_ioctl and compat_ioctl
 * can be called without the big kernel lock held in all filesystems.
 */
struct file_operations {
        struct module *owner;
        loff_t (*llseek) (struct file *, loff_t, int);
        ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
        ssize_t (*aio_read) (struct kiocb *, char __user *, size_t, loff_t);
        ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
        ssize_t (*aio_write) (struct kiocb *, const char __user *, size_t, loff_t);
        int (*readdir) (struct file *, void *, filldir_t);
        unsigned int (*poll) (struct file *, struct poll_table_struct *);
        int (*ioctl) (struct inode *, struct file *, unsigned int, unsigned long);
        long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
        long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
        int (*mmap) (struct file *, struct vm_area_struct *);
        int (*open) (struct inode *, struct file *);
        int (*flush) (struct file *, fl_owner_t id);
        int (*release) (struct inode *, struct file *);
        int (*fsync) (struct file *, struct dentry *, int datasync);
        int (*aio_fsync) (struct kiocb *, int datasync);
        int (*fasync) (int, struct file *, int);
        int (*lock) (struct file *, int, struct file_lock *);
        ssize_t (*readv) (struct file *, const struct iovec *, unsigned long, loff_t *);
        ssize_t (*writev) (struct file *, const struct iovec *, unsigned long, loff_t *);
        ssize_t (*sendfile) (struct file *, loff_t *, size_t, read_actor_t, void *);
        ssize_t (*sendpage) (struct file *, struct page *, int, size_t, loff_t *, int);
        unsigned long (*get_unmapped_area)(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
        int (*check_flags)(int);
        int (*dir_notify)(struct file *filp, unsigned long arg);
        int (*flock) (struct file *, int, struct file_lock *);
        ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *, size_t, unsigned int);
        ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *, size_t, unsigned int);
};

struct inode_operations {
        int (*create) (struct inode *,struct dentry *,int, struct nameidata *);
        struct dentry * (*lookup) (struct inode *,struct dentry *, struct nameidata *);
        int (*link) (struct dentry *,struct inode *,struct dentry *);
        int (*unlink) (struct inode *,struct dentry *);
        int (*symlink) (struct inode *,struct dentry *,const char *);
        int (*mkdir) (struct inode *,struct dentry *,int);
        int (*rmdir) (struct inode *,struct dentry *);
        int (*mknod) (struct inode *,struct dentry *,int,dev_t);
        int (*rename) (struct inode *, struct dentry *,
                        struct inode *, struct dentry *);
        int (*readlink) (struct dentry *, char __user *,int);
        void * (*follow_link) (struct dentry *, struct nameidata *);
        void (*put_link) (struct dentry *, struct nameidata *, void *);
        void (*truncate) (struct inode *);
        int (*permission) (struct inode *, int, struct nameidata *);
        int (*setattr) (struct dentry *, struct iattr *);
        int (*getattr) (struct vfsmount *mnt, struct dentry *, struct kstat *);
        int (*setxattr) (struct dentry *, const char *,const void *,size_t,int);
        ssize_t (*getxattr) (struct dentry *, const char *, void *, size_t);
        ssize_t (*listxattr) (struct dentry *, char *, size_t);
        int (*removexattr) (struct dentry *, const char *);
        void (*truncate_range)(struct inode *, loff_t, loff_t);
};

struct seq_file;

extern ssize_t vfs_read(struct file *, char __user *, size_t, loff_t *);
extern ssize_t vfs_write(struct file *, const char __user *, size_t, loff_t *);
extern ssize_t vfs_readv(struct file *, const struct iovec __user *,
                unsigned long, loff_t *);
extern ssize_t vfs_writev(struct file *, const struct iovec __user *,
                unsigned long, loff_t *);

/*
 * NOTE: write_inode, delete_inode, clear_inode, put_inode can be called
 * without the big kernel lock held in all filesystems.
 */
struct super_operations {
        struct inode *(*alloc_inode)(struct super_block *sb);
        void (*destroy_inode)(struct inode *);

        void (*read_inode) (struct inode *);
  
        void (*dirty_inode) (struct inode *);
        int (*write_inode) (struct inode *, int);
        void (*put_inode) (struct inode *);
        void (*drop_inode) (struct inode *);
        void (*delete_inode) (struct inode *);
        void (*put_super) (struct super_block *);
        void (*write_super) (struct super_block *);
        int (*sync_fs)(struct super_block *sb, int wait);
        void (*write_super_lockfs) (struct super_block *);
        void (*unlockfs) (struct super_block *);
        int (*statfs) (struct dentry *, struct kstatfs *);
        int (*remount_fs) (struct super_block *, int *, char *);
        void (*clear_inode) (struct inode *);
        void (*umount_begin) (struct vfsmount *, int);

        int (*show_options)(struct seq_file *, struct vfsmount *);
        int (*show_stats)(struct seq_file *, struct vfsmount *);

        ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);
        ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
};

/* Inode state bits.  Protected by inode_lock. */
#define I_DIRTY_SYNC            1 /* Not dirty enough for O_DATASYNC */
#define I_DIRTY_DATASYNC        2 /* Data-related inode changes pending */
#define I_DIRTY_PAGES           4 /* Data-related inode changes pending */
#define __I_LOCK                3
#define I_LOCK                  (1 << __I_LOCK)
#define I_FREEING               16
#define I_CLEAR                 32
#define I_NEW                   64
#define I_WILL_FREE             128

#define I_DIRTY (I_DIRTY_SYNC | I_DIRTY_DATASYNC | I_DIRTY_PAGES)

extern void __mark_inode_dirty(struct inode *, int);
static inline void mark_inode_dirty(struct inode *inode)
{
        __mark_inode_dirty(inode, I_DIRTY);
}

static inline void mark_inode_dirty_sync(struct inode *inode)
{
        __mark_inode_dirty(inode, I_DIRTY_SYNC);
}

static inline void inode_inc_link_count(struct inode *inode)
{
        inode->i_nlink++;
        mark_inode_dirty(inode);
}

static inline void inode_dec_link_count(struct inode *inode)
{
        inode->i_nlink--;
        mark_inode_dirty(inode);
}

extern void touch_atime(struct vfsmount *mnt, struct dentry *dentry);
static inline void file_accessed(struct file *file)
{
        if (!(file->f_flags & O_NOATIME))
                touch_atime(file->f_vfsmnt, file->f_dentry);
}

int sync_inode(struct inode *inode, struct writeback_control *wbc);

/**
 * struct export_operations - for nfsd to communicate with file systems
 * @decode_fh:      decode a file handle fragment and return a &struct dentry
 * @encode_fh:      encode a file handle fragment from a dentry
 * @get_name:       find the name for a given inode in a given directory
 * @get_parent:     find the parent of a given directory
 * @get_dentry:     find a dentry for the inode given a file handle sub-fragment
 * @find_exported_dentry:
 *      set by the exporting module to a standard helper function.
 *
 * Description:
 *    The export_operations structure provides a means for nfsd to communicate
 *    with a particular exported file system  - particularly enabling nfsd and
 *    the filesystem to co-operate when dealing with file handles.
 *
 *    export_operations contains two basic operation for dealing with file
 *    handles, decode_fh() and encode_fh(), and allows for some other
 *    operations to be defined which standard helper routines use to get
 *    specific information from the filesystem.
 *
 *    nfsd encodes information use to determine which filesystem a filehandle
 *    applies to in the initial part of the file handle.  The remainder, termed
 *    a file handle fragment, is controlled completely by the filesystem.  The
 *    standard helper routines assume that this fragment will contain one or
 *    two sub-fragments, one which identifies the file, and one which may be
 *    used to identify the (a) directory containing the file.
 *
 *    In some situations, nfsd needs to get a dentry which is connected into a
 *    specific part of the file tree.  To allow for this, it passes the
 *    function acceptable() together with a @context which can be used to see
 *    if the dentry is acceptable.  As there can be multiple dentrys for a
 *    given file, the filesystem should check each one for acceptability before
 *    looking for the next.  As soon as an acceptable one is found, it should
 *    be returned.
 *
 * decode_fh:
 *    @decode_fh is given a &struct super_block (@sb), a file handle fragment
 *    (@fh, @fh_len) and an acceptability testing function (@acceptable,
 *    @context).  It should return a &struct dentry which refers to the same
 *    file that the file handle fragment refers to,  and which passes the
 *    acceptability test.  If it cannot, it should return a %NULL pointer if
 *    the file was found but no acceptable &dentries were available, or a
 *    %ERR_PTR error code indicating why it couldn't be found (e.g. %ENOENT or
 *    %ENOMEM).
 *
 * encode_fh:
 *    @encode_fh should store in the file handle fragment @fh (using at most
 *    @max_len bytes) information that can be used by @decode_fh to recover the
 *    file refered to by the &struct dentry @de.  If the @connectable flag is
 *    set, the encode_fh() should store sufficient information so that a good
 *    attempt can be made to find not only the file but also it's place in the
 *    filesystem.   This typically means storing a reference to de->d_parent in
 *    the filehandle fragment.  encode_fh() should return the number of bytes
 *    stored or a negative error code such as %-ENOSPC
 *
 * get_name:
 *    @get_name should find a name for the given @child in the given @parent
 *    directory.  The name should be stored in the @name (with the
 *    understanding that it is already pointing to a a %NAME_MAX+1 sized
 *    buffer.   get_name() should return %0 on success, a negative error code
 *    or error.  @get_name will be called without @parent->i_mutex held.
 *
 * get_parent:
 *    @get_parent should find the parent directory for the given @child which
 *    is also a directory.  In the event that it cannot be found, or storage
 *    space cannot be allocated, a %ERR_PTR should be returned.
 *
 * get_dentry:
 *    Given a &super_block (@sb) and a pointer to a file-system specific inode
 *    identifier, possibly an inode number, (@inump) get_dentry() should find
 *    the identified inode and return a dentry for that inode.  Any suitable
 *    dentry can be returned including, if necessary, a new dentry created with
 *    d_alloc_root.  The caller can then find any other extant dentrys by
 *    following the d_alias links.  If a new dentry was created using
 *    d_alloc_root, DCACHE_NFSD_DISCONNECTED should be set, and the dentry
 *    should be d_rehash()ed.
 *
 *    If the inode cannot be found, either a %NULL pointer or an %ERR_PTR code
 *    can be returned.  The @inump will be whatever was passed to
 *    nfsd_find_fh_dentry() in either the @obj or @parent parameters.
 *
 * Locking rules:
 *    get_parent is called with child->d_inode->i_mutex down
 *    get_name is not (which is possibly inconsistent)
 */

struct export_operations {
        struct dentry *(*decode_fh)(struct super_block *sb, __u32 *fh, int fh_len, int fh_type,
                         int (*acceptable)(void *context, struct dentry *de),
                         void *context);
        int (*encode_fh)(struct dentry *de, __u32 *fh, int *max_len,
                         int connectable);

        /* the following are only called from the filesystem itself */
        int (*get_name)(struct dentry *parent, char *name,
                        struct dentry *child);
        struct dentry * (*get_parent)(struct dentry *child);
        struct dentry * (*get_dentry)(struct super_block *sb, void *inump);

        /* This is set by the exporting module to a standard helper */
        struct dentry * (*find_exported_dentry)(
                struct super_block *sb, void *obj, void *parent,
                int (*acceptable)(void *context, struct dentry *de),
                void *context);


};

extern struct dentry *
find_exported_dentry(struct super_block *sb, void *obj, void *parent,
                     int (*acceptable)(void *context, struct dentry *de),
                     void *context);

struct file_system_type {
        const char *name;
        int fs_flags;
        int (*get_sb) (struct file_system_type *, int,
                       const char *, void *, struct vfsmount *);
        void (*kill_sb) (struct super_block *);
        struct module *owner;
        struct file_system_type * next;
        struct list_head fs_supers;
        struct lock_class_key s_lock_key;
        struct lock_class_key s_umount_key;
};

extern int get_sb_bdev(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *data,
        int (*fill_super)(struct super_block *, void *, int),
        struct vfsmount *mnt);
extern int get_sb_single(struct file_system_type *fs_type,
        int flags, void *data,
        int (*fill_super)(struct super_block *, void *, int),
        struct vfsmount *mnt);
extern int get_sb_nodev(struct file_system_type *fs_type,
        int flags, void *data,
        int (*fill_super)(struct super_block *, void *, int),
        struct vfsmount *mnt);
void generic_shutdown_super(struct super_block *sb);
void kill_block_super(struct super_block *sb);
void kill_anon_super(struct super_block *sb);
void kill_litter_super(struct super_block *sb);
void deactivate_super(struct super_block *sb);
int set_anon_super(struct super_block *s, void *data);
struct super_block *sget(struct file_system_type *type,
                        int (*test)(struct super_block *,void *),
                        int (*set)(struct super_block *,void *),
                        void *data);
extern int get_sb_pseudo(struct file_system_type *, char *,
        struct super_operations *ops, unsigned long,
        struct vfsmount *mnt);
extern int simple_set_mnt(struct vfsmount *mnt, struct super_block *sb);
int __put_super(struct super_block *sb);
int __put_super_and_need_restart(struct super_block *sb);
void unnamed_dev_init(void);

/* Alas, no aliases. Too much hassle with bringing module.h everywhere */
#define fops_get(fops) \
        (((fops) && try_module_get((fops)->owner) ? (fops) : NULL))
#define fops_put(fops) \
        do { if (fops) module_put((fops)->owner); } while(0)

extern int register_filesystem(struct file_system_type *);
extern int unregister_filesystem(struct file_system_type *);
extern struct vfsmount *kern_mount(struct file_system_type *);
extern int may_umount_tree(struct vfsmount *);
extern int may_umount(struct vfsmount *);
extern void umount_tree(struct vfsmount *, int, struct list_head *);
extern void release_mounts(struct list_head *);
extern long do_mount(char *, char *, char *, unsigned long, void *);
extern struct vfsmount *copy_tree(struct vfsmount *, struct dentry *, int);
extern void mnt_set_mountpoint(struct vfsmount *, struct dentry *,
                                  struct vfsmount *);

extern int vfs_statfs(struct dentry *, struct kstatfs *);

/* /sys/fs */
extern struct subsystem fs_subsys;

#define FLOCK_VERIFY_READ  1
#define FLOCK_VERIFY_WRITE 2

extern int locks_mandatory_locked(struct inode *);
extern int locks_mandatory_area(int, struct inode *, struct file *, loff_t, size_t);

/*
 * Candidates for mandatory locking have the setgid bit set
 * but no group execute bit -  an otherwise meaningless combination.
 */
#define MANDATORY_LOCK(inode) \
        (IS_MANDLOCK(inode) && ((inode)->i_mode & (S_ISGID | S_IXGRP)) == S_ISGID)

static inline int locks_verify_locked(struct inode *inode)
{
        if (MANDATORY_LOCK(inode))
                return locks_mandatory_locked(inode);
        return 0;
}

extern int rw_verify_area(int, struct file *, loff_t *, size_t);

static inline int locks_verify_truncate(struct inode *inode,
                                    struct file *filp,
                                    loff_t size)
{
        if (inode->i_flock && MANDATORY_LOCK(inode))
                return locks_mandatory_area(
                        FLOCK_VERIFY_WRITE, inode, filp,
                        size < inode->i_size ? size : inode->i_size,
                        (size < inode->i_size ? inode->i_size - size
                         : size - inode->i_size)
                );
        return 0;
}

static inline int break_lease(struct inode *inode, unsigned int mode)
{
        if (inode->i_flock)
                return __break_lease(inode, mode);
        return 0;
}

/* fs/open.c */

extern int do_truncate(struct dentry *, loff_t start, unsigned int time_attrs,
                       struct file *filp);
extern long do_sys_open(int fdf, const char __user *filename, int flags,
                        int mode);
extern struct file *filp_open(const char *, int, int);
extern struct file * dentry_open(struct dentry *, struct vfsmount *, int);
extern int filp_close(struct file *, fl_owner_t id);
extern char * getname(const char __user *);

/* fs/dcache.c */
extern void __init vfs_caches_init_early(void);
extern void __init vfs_caches_init(unsigned long);

#define __getname()     kmem_cache_alloc(names_cachep, SLAB_KERNEL)
#define __putname(name) kmem_cache_free(names_cachep, (void *)(name))
#ifndef CONFIG_AUDITSYSCALL
#define putname(name)   __putname(name)
#else
extern void putname(const char *name);
#endif

extern int register_blkdev(unsigned int, const char *);
extern int unregister_blkdev(unsigned int, const char *);
extern struct block_device *bdget(dev_t);
extern void bd_set_size(struct block_device *, loff_t size);
extern void bd_forget(struct inode *inode);
extern void bdput(struct block_device *);
extern struct block_device *open_by_devnum(dev_t, unsigned);
extern struct block_device *open_partition_by_devnum(dev_t, unsigned);
extern const struct file_operations def_blk_fops;
extern const struct address_space_operations def_blk_aops;
extern const struct file_operations def_chr_fops;
extern const struct file_operations bad_sock_fops;
extern const struct file_operations def_fifo_fops;
extern int ioctl_by_bdev(struct block_device *, unsigned, unsigned long);
extern int blkdev_ioctl(struct inode *, struct file *, unsigned, unsigned long);
extern long compat_blkdev_ioctl(struct file *, unsigned, unsigned long);
extern int blkdev_get(struct block_device *, mode_t, unsigned);
extern int blkdev_put(struct block_device *);
extern int blkdev_put_partition(struct block_device *);
extern int bd_claim(struct block_device *, void *);
extern void bd_release(struct block_device *);
#ifdef CONFIG_SYSFS
extern int bd_claim_by_disk(struct block_device *, void *, struct gendisk *);
extern void bd_release_from_disk(struct block_device *, struct gendisk *);
#else
#define bd_claim_by_disk(bdev, holder, disk)    bd_claim(bdev, holder)
#define bd_release_from_disk(bdev, disk)        bd_release(bdev)
#endif

/* fs/char_dev.c */
#define CHRDEV_MAJOR_HASH_SIZE  255
extern int alloc_chrdev_region(dev_t *, unsigned, unsigned, const char *);
extern int register_chrdev_region(dev_t, unsigned, const char *);
extern int register_chrdev(unsigned int, const char *,
                           const struct file_operations *);
extern int unregister_chrdev(unsigned int, const char *);
extern void unregister_chrdev_region(dev_t, unsigned);
extern int chrdev_open(struct inode *, struct file *);
extern void chrdev_show(struct seq_file *,off_t);

/* fs/block_dev.c */
#define BLKDEV_MAJOR_HASH_SIZE  255
#define BDEVNAME_SIZE   32      /* Largest string for a blockdev identifier */
extern const char *__bdevname(dev_t, char *buffer);
extern const char *bdevname(struct block_device *bdev, char *buffer);
extern struct block_device *lookup_bdev(const char *);
extern struct block_device *open_bdev_excl(const char *, int, void *);
extern void close_bdev_excl(struct block_device *);
extern void blkdev_show(struct seq_file *,off_t);

extern void init_special_inode(struct inode *, umode_t, dev_t);

/* Invalid inode operations -- fs/bad_inode.c */
extern void make_bad_inode(struct inode *);
extern int is_bad_inode(struct inode *);

extern const struct file_operations read_fifo_fops;
extern const struct file_operations write_fifo_fops;
extern const struct file_operations rdwr_fifo_fops;

extern int fs_may_remount_ro(struct super_block *);

/*
 * return READ, READA, or WRITE
 */
#define bio_rw(bio)             ((bio)->bi_rw & (RW_MASK | RWA_MASK))

/*
 * return data direction, READ or WRITE
 */
#define bio_data_dir(bio)       ((bio)->bi_rw & 1)

extern int check_disk_change(struct block_device *);
extern int invalidate_inodes(struct super_block *);
extern int __invalidate_device(struct block_device *);
extern int invalidate_partition(struct gendisk *, int);
unsigned long invalidate_mapping_pages(struct address_space *mapping,
                                        pgoff_t start, pgoff_t end);
unsigned long invalidate_inode_pages(struct address_space *mapping);
static inline void invalidate_remote_inode(struct inode *inode)
{
        if (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) ||
            S_ISLNK(inode->i_mode))
                invalidate_inode_pages(inode->i_mapping);
}
extern int invalidate_inode_pages2(struct address_space *mapping);
extern int invalidate_inode_pages2_range(struct address_space *mapping,
                                         pgoff_t start, pgoff_t end);
extern int write_inode_now(struct inode *, int);
extern int filemap_fdatawrite(struct address_space *);
extern int filemap_flush(struct address_space *);
extern int filemap_fdatawait(struct address_space *);
extern int filemap_write_and_wait(struct address_space *mapping);
extern int filemap_write_and_wait_range(struct address_space *mapping,
                                        loff_t lstart, loff_t lend);
extern int wait_on_page_writeback_range(struct address_space *mapping,
                                pgoff_t start, pgoff_t end);
extern int __filemap_fdatawrite_range(struct address_space *mapping,
                                loff_t start, loff_t end, int sync_mode);

extern long do_fsync(struct file *file, int datasync);
extern void sync_supers(void);
extern void sync_filesystems(int wait);
extern void emergency_sync(void);
extern void emergency_remount(void);
extern int do_remount_sb(struct super_block *sb, int flags,
                         void *data, int force);
extern sector_t bmap(struct inode *, sector_t);
extern int notify_change(struct dentry *, struct iattr *);
extern int permission(struct inode *, int, struct nameidata *);
extern int generic_permission(struct inode *, int,
                int (*check_acl)(struct inode *, int));

extern int get_write_access(struct inode *);
extern int deny_write_access(struct file *);
static inline void put_write_access(struct inode * inode)
{
        atomic_dec(&inode->i_writecount);
}
static inline void allow_write_access(struct file *file)
{
        if (file)
                atomic_inc(&file->f_dentry->d_inode->i_writecount);
}
extern int do_pipe(int *);

extern int open_namei(int dfd, const char *, int, int, struct nameidata *);
extern int may_open(struct nameidata *, int, int);

extern int kernel_read(struct file *, unsigned long, char *, unsigned long);
extern struct file * open_exec(const char *);
 
/* fs/dcache.c -- generic fs support functions */
extern int is_subdir(struct dentry *, struct dentry *);
extern ino_t find_inode_number(struct dentry *, struct qstr *);

#include <linux/err.h>

/* needed for stackable file system support */
extern loff_t default_llseek(struct file *file, loff_t offset, int origin);

extern loff_t vfs_llseek(struct file *file, loff_t offset, int origin);

extern void inode_init_once(struct inode *);
extern void iput(struct inode *);
extern struct inode * igrab(struct inode *);
extern ino_t iunique(struct super_block *, ino_t);
extern int inode_needs_sync(struct inode *inode);
extern void generic_delete_inode(struct inode *inode);
extern void generic_drop_inode(struct inode *inode);

extern struct inode *ilookup5_nowait(struct super_block *sb,
                unsigned long hashval, int (*test)(struct inode *, void *),
                void *data);
extern struct inode *ilookup5(struct super_block *sb, unsigned long hashval,
                int (*test)(struct inode *, void *), void *data);
extern struct inode *ilookup(struct super_block *sb, unsigned long ino);

extern struct inode * iget5_locked(struct super_block *, unsigned long, int (*test)(struct inode *, void *), int (*set)(struct inode *, void *), void *);
extern struct inode * iget_locked(struct super_block *, unsigned long);
extern void unlock_new_inode(struct inode *);

static inline struct inode *iget(struct super_block *sb, unsigned long ino)
{
        struct inode *inode = iget_locked(sb, ino);
        
        if (inode && (inode->i_state & I_NEW)) {
                sb->s_op->read_inode(inode);
                unlock_new_inode(inode);
        }

        return inode;
}

extern void __iget(struct inode * inode);
extern void clear_inode(struct inode *);
extern void destroy_inode(struct inode *);
extern struct inode *new_inode(struct super_block *);
extern int remove_suid(struct dentry *);
extern void remove_dquot_ref(struct super_block *, int, struct list_head *);

extern void __insert_inode_hash(struct inode *, unsigned long hashval);
extern void remove_inode_hash(struct inode *);
static inline void insert_inode_hash(struct inode *inode) {
        __insert_inode_hash(inode, inode->i_ino);
}

extern struct file * get_empty_filp(void);
extern void file_move(struct file *f, struct list_head *list);
extern void file_kill(struct file *f);
struct bio;
extern void submit_bio(int, struct bio *);
extern int bdev_read_only(struct block_device *);
extern int set_blocksize(struct block_device *, int);
extern int sb_set_blocksize(struct super_block *, int);
extern int sb_min_blocksize(struct super_block *, int);

extern int generic_file_mmap(struct file *, struct vm_area_struct *);
extern int generic_file_readonly_mmap(struct file *, struct vm_area_struct *);
extern int file_read_actor(read_descriptor_t * desc, struct page *page, unsigned long offset, unsigned long size);
extern int file_send_actor(read_descriptor_t * desc, struct page *page, unsigned long offset, unsigned long size);
extern ssize_t generic_file_read(struct file *, char __user *, size_t, loff_t *);
int generic_write_checks(struct file *file, loff_t *pos, size_t *count, int isblk);
extern ssize_t generic_file_write(struct file *, const char __user *, size_t, loff_t *);
extern ssize_t generic_file_aio_read(struct kiocb *, char __user *, size_t, loff_t);
extern ssize_t __generic_file_aio_read(struct kiocb *, const struct iovec *, unsigned long, loff_t *);
extern ssize_t generic_file_aio_write(struct kiocb *, const char __user *, size_t, loff_t);
extern ssize_t generic_file_aio_write_nolock(struct kiocb *, const struct iovec *,
                unsigned long, loff_t *);
extern ssize_t generic_file_direct_write(struct kiocb *, const struct iovec *,
                unsigned long *, loff_t, loff_t *, size_t, size_t);
extern ssize_t generic_file_buffered_write(struct kiocb *, const struct iovec *,
                unsigned long, loff_t, loff_t *, size_t, ssize_t);
extern ssize_t do_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos);
extern ssize_t do_sync_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos);
ssize_t generic_file_write_nolock(struct file *file, const struct iovec *iov,
                                unsigned long nr_segs, loff_t *ppos);
extern ssize_t generic_file_sendfile(struct file *, loff_t *, size_t, read_actor_t, void *);
extern void do_generic_mapping_read(struct address_space *mapping,
                                    struct file_ra_state *, struct file *,
                                    loff_t *, read_descriptor_t *, read_actor_t);

/* fs/splice.c */
extern ssize_t generic_file_splice_read(struct file *, loff_t *,
                struct pipe_inode_info *, size_t, unsigned int);
extern ssize_t generic_file_splice_write(struct pipe_inode_info *,
                struct file *, loff_t *, size_t, unsigned int);
extern ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe,
                struct file *out, loff_t *, size_t len, unsigned int flags);
extern long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
                size_t len, unsigned int flags);

extern void
file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping);
extern ssize_t generic_file_readv(struct file *filp, const struct iovec *iov, 
        unsigned long nr_segs, loff_t *ppos);
ssize_t generic_file_writev(struct file *filp, const struct iovec *iov, 
                        unsigned long nr_segs, loff_t *ppos);
extern loff_t no_llseek(struct file *file, loff_t offset, int origin);
extern loff_t generic_file_llseek(struct file *file, loff_t offset, int origin);
extern loff_t remote_llseek(struct file *file, loff_t offset, int origin);
extern int generic_file_open(struct inode * inode, struct file * filp);
extern int nonseekable_open(struct inode * inode, struct file * filp);

#ifdef CONFIG_FS_XIP
extern ssize_t xip_file_read(struct file *filp, char __user *buf, size_t len,
                             loff_t *ppos);
extern ssize_t xip_file_sendfile(struct file *in_file, loff_t *ppos,
                                 size_t count, read_actor_t actor,
                                 void *target);
extern int xip_file_mmap(struct file * file, struct vm_area_struct * vma);
extern ssize_t xip_file_write(struct file *filp, const char __user *buf,
                              size_t len, loff_t *ppos);
extern int xip_truncate_page(struct address_space *mapping, loff_t from);
#else
static inline int xip_truncate_page(struct address_space *mapping, loff_t from)
{
        return 0;
}
#endif

static inline void do_generic_file_read(struct file * filp, loff_t *ppos,
                                        read_descriptor_t * desc,
                                        read_actor_t actor)
{
        do_generic_mapping_read(filp->f_mapping,
                                &filp->f_ra,
                                filp,
                                ppos,
                                desc,
                                actor);
}

ssize_t __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode,
        struct block_device *bdev, const struct iovec *iov, loff_t offset,
        unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io,
        int lock_type);

enum {
        DIO_LOCKING = 1, /* need locking between buffered and direct access */
        DIO_NO_LOCKING,  /* bdev; no locking at all between buffered/direct */
        DIO_OWN_LOCKING, /* filesystem locks buffered and direct internally */
};

static inline ssize_t blockdev_direct_IO(int rw, struct kiocb *iocb,
        struct inode *inode, struct block_device *bdev, const struct iovec *iov,
        loff_t offset, unsigned long nr_segs, get_block_t get_block,
        dio_iodone_t end_io)
{
        return __blockdev_direct_IO(rw, iocb, inode, bdev, iov, offset,
                                nr_segs, get_block, end_io, DIO_LOCKING);
}

static inline ssize_t blockdev_direct_IO_no_locking(int rw, struct kiocb *iocb,
        struct inode *inode, struct block_device *bdev, const struct iovec *iov,
        loff_t offset, unsigned long nr_segs, get_block_t get_block,
        dio_iodone_t end_io)
{
        return __blockdev_direct_IO(rw, iocb, inode, bdev, iov, offset,
                                nr_segs, get_block, end_io, DIO_NO_LOCKING);
}

static inline ssize_t blockdev_direct_IO_own_locking(int rw, struct kiocb *iocb,
        struct inode *inode, struct block_device *bdev, const struct iovec *iov,
        loff_t offset, unsigned long nr_segs, get_block_t get_block,
        dio_iodone_t end_io)
{
        return __blockdev_direct_IO(rw, iocb, inode, bdev, iov, offset,
                                nr_segs, get_block, end_io, DIO_OWN_LOCKING);
}

extern const struct file_operations generic_ro_fops;

#define special_file(m) (S_ISCHR(m)||S_ISBLK(m)||S_ISFIFO(m)||S_ISSOCK(m))

extern int vfs_readlink(struct dentry *, char __user *, int, const char *);
extern int vfs_follow_link(struct nameidata *, const char *);
extern int page_readlink(struct dentry *, char __user *, int);
extern void *page_follow_link_light(struct dentry *, struct nameidata *);
extern void page_put_link(struct dentry *, struct nameidata *, void *);
extern int __page_symlink(struct inode *inode, const char *symname, int len,
                gfp_t gfp_mask);
extern int page_symlink(struct inode *inode, const char *symname, int len);
extern struct inode_operations page_symlink_inode_operations;
extern int generic_readlink(struct dentry *, char __user *, int);
extern void generic_fillattr(struct inode *, struct kstat *);
extern int vfs_getattr(struct vfsmount *, struct dentry *, struct kstat *);
void inode_add_bytes(struct inode *inode, loff_t bytes);
void inode_sub_bytes(struct inode *inode, loff_t bytes);
loff_t inode_get_bytes(struct inode *inode);
void inode_set_bytes(struct inode *inode, loff_t bytes);

extern int vfs_readdir(struct file *, filldir_t, void *);

extern int vfs_stat(char __user *, struct kstat *);
extern int vfs_lstat(char __user *, struct kstat *);
extern int vfs_stat_fd(int dfd, char __user *, struct kstat *);
extern int vfs_lstat_fd(int dfd, char __user *, struct kstat *);
extern int vfs_fstat(unsigned int, struct kstat *);

extern int vfs_ioctl(struct file *, unsigned int, unsigned int, unsigned long);

extern struct file_system_type *get_fs_type(const char *name);
extern struct super_block *get_super(struct block_device *);
extern struct super_block *user_get_super(dev_t);
extern void drop_super(struct super_block *sb);

extern int dcache_dir_open(struct inode *, struct file *);
extern int dcache_dir_close(struct inode *, struct file *);
extern loff_t dcache_dir_lseek(struct file *, loff_t, int);
extern int dcache_readdir(struct file *, void *, filldir_t);
extern int simple_getattr(struct vfsmount *, struct dentry *, struct kstat *);
extern int simple_statfs(struct dentry *, struct kstatfs *);
extern int simple_link(struct dentry *, struct inode *, struct dentry *);
extern int simple_unlink(struct inode *, struct dentry *);
extern int simple_rmdir(struct inode *, struct dentry *);
extern int simple_rename(struct inode *, struct dentry *, struct inode *, struct dentry *);
extern int simple_sync_file(struct file *, struct dentry *, int);
extern int simple_empty(struct dentry *);
extern int simple_readpage(struct file *file, struct page *page);
extern int simple_prepare_write(struct file *file, struct page *page,
                        unsigned offset, unsigned to);
extern int simple_commit_write(struct file *file, struct page *page,
                                unsigned offset, unsigned to);

extern struct dentry *simple_lookup(struct inode *, struct dentry *, struct nameidata *);
extern ssize_t generic_read_dir(struct file *, char __user *, size_t, loff_t *);
extern const struct file_operations simple_dir_operations;
extern struct inode_operations simple_dir_inode_operations;
struct tree_descr { char *name; const struct file_operations *ops; int mode; };
struct dentry *d_alloc_name(struct dentry *, const char *);
extern int simple_fill_super(struct super_block *, int, struct tree_descr *);
extern int simple_pin_fs(struct file_system_type *, struct vfsmount **mount, int *count);
extern void simple_release_fs(struct vfsmount **mount, int *count);

extern ssize_t simple_read_from_buffer(void __user *, size_t, loff_t *, const void *, size_t);

#ifdef CONFIG_MIGRATION
extern int buffer_migrate_page(struct address_space *,
                                struct page *, struct page *);
#else
#define buffer_migrate_page NULL
#endif

extern int inode_change_ok(struct inode *, struct iattr *);
extern int __must_check inode_setattr(struct inode *, struct iattr *);

extern void file_update_time(struct file *file);

static inline ino_t parent_ino(struct dentry *dentry)
{
        ino_t res;

        spin_lock(&dentry->d_lock);
        res = dentry->d_parent->d_inode->i_ino;
        spin_unlock(&dentry->d_lock);
        return res;
}

/* kernel/fork.c */
extern int unshare_files(void);

/* Transaction based IO helpers */

/*
 * An argresp is stored in an allocated page and holds the
 * size of the argument or response, along with its content
 */
struct simple_transaction_argresp {
        ssize_t size;
        char data[0];
};

#define SIMPLE_TRANSACTION_LIMIT (PAGE_SIZE - sizeof(struct simple_transaction_argresp))

char *simple_transaction_get(struct file *file, const char __user *buf,
                                size_t size);
ssize_t simple_transaction_read(struct file *file, char __user *buf,
                                size_t size, loff_t *pos);
int simple_transaction_release(struct inode *inode, struct file *file);

static inline void simple_transaction_set(struct file *file, size_t n)
{
        struct simple_transaction_argresp *ar = file->private_data;

        BUG_ON(n > SIMPLE_TRANSACTION_LIMIT);

        /*
         * The barrier ensures that ar->size will really remain zero until
         * ar->data is ready for reading.
         */
        smp_mb();
        ar->size = n;
}

/*
 * simple attribute files
 *
 * These attributes behave similar to those in sysfs:
 *
 * Writing to an attribute immediately sets a value, an open file can be
 * written to multiple times.
 *
 * Reading from an attribute creates a buffer from the value that might get
 * read with multiple read calls. When the attribute has been read
 * completely, no further read calls are possible until the file is opened
 * again.
 *
 * All attributes contain a text representation of a numeric value
 * that are accessed with the get() and set() functions.
 */
#define DEFINE_SIMPLE_ATTRIBUTE(__fops, __get, __set, __fmt)            \
static int __fops ## _open(struct inode *inode, struct file *file)      \
{                                                                       \
        __simple_attr_check_format(__fmt, 0ull);                        \
        return simple_attr_open(inode, file, __get, __set, __fmt);      \
}                                                                       \
static struct file_operations __fops = {                                \
        .owner   = THIS_MODULE,                                         \
        .open    = __fops ## _open,                                     \
        .release = simple_attr_close,                                   \
        .read    = simple_attr_read,                                    \
        .write   = simple_attr_write,                                   \
};

static inline void __attribute__((format(printf, 1, 2)))
__simple_attr_check_format(const char *fmt, ...)
{
        /* don't do anything, just let the compiler check the arguments; */
}

int simple_attr_open(struct inode *inode, struct file *file,
                     u64 (*get)(void *), void (*set)(void *, u64),
                     const char *fmt);
int simple_attr_close(struct inode *inode, struct file *file);
ssize_t simple_attr_read(struct file *file, char __user *buf,
                         size_t len, loff_t *ppos);
ssize_t simple_attr_write(struct file *file, const char __user *buf,
                          size_t len, loff_t *ppos);


#ifdef CONFIG_SECURITY
static inline char *alloc_secdata(void)
{
        return (char *)get_zeroed_page(GFP_KERNEL);
}

static inline void free_secdata(void *secdata)
{
        free_page((unsigned long)secdata);
}
#else
static inline char *alloc_secdata(void)
{
        return (char *)1;
}

static inline void free_secdata(void *secdata)
{ }
#endif  /* CONFIG_SECURITY */

#endif /* __KERNEL__ */
#endif /* _LINUX_FS_H */