fs/9p: Fix race in initializing writeback fid

When two process open the same file we can end up with both of them
allocating the writeback_fid. Add a new mutex which can be used
for synchronizing v9fs_inode member values.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>

diff --git a/fs/9p/v9fs.h b/fs/9p/v9fs.h
index bd8496d..89657e8 100644 (file)
--- a/fs/9p/v9fs.h
+++ b/fs/9p/v9fs.h
@@ -130,6 +130,7 @@ struct v9fs_inode {
 #endif
        unsigned int cache_validity;
        struct p9_fid *writeback_fid;
+       struct mutex v_mutex;
        struct inode vfs_inode;
 };
 

diff --git a/fs/9p/vfs_file.c b/fs/9p/vfs_file.c
index 78bcb97..3337d58 100644 (file)
--- a/fs/9p/vfs_file.c
+++ b/fs/9p/vfs_file.c
@@ -90,6 +90,7 @@ int v9fs_file_open(struct inode *inode, struct file *file)
        }
 
        file->private_data = fid;
+       mutex_lock(&v9inode->v_mutex);
        if (v9ses->cache && !v9inode->writeback_fid) {
                /*
                 * clone a fid and add it to writeback_fid
@@ -101,10 +102,12 @@ int v9fs_file_open(struct inode *inode, struct file *file)
                fid = v9fs_writeback_fid(file->f_path.dentry);
                if (IS_ERR(fid)) {
                        err = PTR_ERR(fid);
+                       mutex_unlock(&v9inode->v_mutex);
                        goto out_error;
                }
                v9inode->writeback_fid = (void *) fid;
        }
+       mutex_unlock(&v9inode->v_mutex);
 #ifdef CONFIG_9P_FSCACHE
        if (v9ses->cache)
                v9fs_cache_inode_set_cookie(inode, file);

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index 8a2c232..c6cef24 100644 (file)
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -221,6 +221,7 @@ struct inode *v9fs_alloc_inode(struct super_block *sb)
 #endif
        v9inode->writeback_fid = NULL;
        v9inode->cache_validity = 0;
+       mutex_init(&v9inode->v_mutex);
        return &v9inode->vfs_inode;
 }
 
@@ -650,6 +651,7 @@ v9fs_vfs_create(struct inode *dir, struct dentry *dentry, int mode,
        /* if we are opening a file, assign the open fid to the file */
        if (nd && nd->flags & LOOKUP_OPEN) {
                v9inode = V9FS_I(dentry->d_inode);
+               mutex_lock(&v9inode->v_mutex);
                if (v9ses->cache && !v9inode->writeback_fid) {
                        /*
                         * clone a fid and add it to writeback_fid
@@ -661,10 +663,12 @@ v9fs_vfs_create(struct inode *dir, struct dentry *dentry, int mode,
                        inode_fid = v9fs_writeback_fid(dentry);
                        if (IS_ERR(inode_fid)) {
                                err = PTR_ERR(inode_fid);
+                               mutex_unlock(&v9inode->v_mutex);
                                goto error;
                        }
                        v9inode->writeback_fid = (void *) inode_fid;
                }
+               mutex_unlock(&v9inode->v_mutex);
                filp = lookup_instantiate_filp(nd, dentry, generic_file_open);
                if (IS_ERR(filp)) {
                        err = PTR_ERR(filp);

diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
index 67c138e..327c578 100644 (file)
--- a/fs/9p/vfs_inode_dotl.c
+++ b/fs/9p/vfs_inode_dotl.c
@@ -245,6 +245,7 @@ v9fs_vfs_create_dotl(struct inode *dir, struct dentry *dentry, int omode,
        v9fs_set_create_acl(dentry, dacl, pacl);
 
        v9inode = V9FS_I(inode);
+       mutex_lock(&v9inode->v_mutex);
        if (v9ses->cache && !v9inode->writeback_fid) {
                /*
                 * clone a fid and add it to writeback_fid
@@ -256,10 +257,12 @@ v9fs_vfs_create_dotl(struct inode *dir, struct dentry *dentry, int omode,
                inode_fid = v9fs_writeback_fid(dentry);
                if (IS_ERR(inode_fid)) {
                        err = PTR_ERR(inode_fid);
+                       mutex_unlock(&v9inode->v_mutex);
                        goto error;
                }
                v9inode->writeback_fid = (void *) inode_fid;
        }
+       mutex_unlock(&v9inode->v_mutex);
        /* Since we are opening a file, assign the open fid to the file */
        filp = lookup_instantiate_filp(nd, dentry, generic_file_open);
        if (IS_ERR(filp)) {