vfs: reorganize 'struct inode' layout a bit

This tries to make the 'struct inode' accesses denser in the data cache
by moving a commonly accessed field (i_security) closer to other fields
that are accessed often.

It also makes 'i_state' just an 'unsigned int' rather than 'unsigned
long', since we only use a few bits of that field, and moves it next to
the existing 'i_flags' so that we potentially get better structure
layout (although depending on config options, i_flags may already have
packed in the same word as i_lock, so this improves packing only for the
case of spinlock debugging)

Out 'struct inode' is still way too big, and we should probably move
some other fields around too (the acl fields in particular) for better
data cache access density.  Other fields (like the inode hash) are
likely to be entirely irrelevant under most loads.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 646a183..1c77787 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -744,9 +744,13 @@ struct inode {
 
        spinlock_t              i_lock; /* i_blocks, i_bytes, maybe i_size */
        unsigned int            i_flags;
+       unsigned int            i_state;
+#ifdef CONFIG_SECURITY
+       void                    *i_security;
+#endif
        struct mutex            i_mutex;
 
-       unsigned long           i_state;
+
        unsigned long           dirtied_when;   /* jiffies of first dirtying */
 
        struct hlist_node       i_hash;
@@ -798,9 +802,6 @@ struct inode {
        atomic_t                i_readcount; /* struct files open RO */
 #endif
        atomic_t                i_writecount;
-#ifdef CONFIG_SECURITY
-       void                    *i_security;
-#endif
 #ifdef CONFIG_FS_POSIX_ACL
        struct posix_acl        *i_acl;
        struct posix_acl        *i_default_acl;