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authorMiklos Szeredi <mszeredi@suse.cz>2012-06-05 15:10:17 +0200
committerAl Viro <viro@zeniv.linux.org.uk>2012-07-14 16:33:04 +0400
commitd18e9008c377dc6a6d2166a6840bf3a23a5867fd (patch)
tree6bbb29aea7e931b603bd4cea3cc74a0eda7b6379 /Documentation/filesystems/vfs.txt
parent54ef487241e863a6046536ac5b1fcd5d7cde86e5 (diff)
vfs: add i_op->atomic_open()
Add a new inode operation which is called on the last component of an open. Using this the filesystem can look up, possibly create and open the file in one atomic operation. If it cannot perform this (e.g. the file type turned out to be wrong) it may signal this by returning NULL instead of an open struct file pointer. i_op->atomic_open() is only called if the last component is negative or needs lookup. Handling cached positive dentries here doesn't add much value: these can be opened using f_op->open(). If the cached file turns out to be invalid, the open can be retried, this time using ->atomic_open() with a fresh dentry. For now leave the old way of using open intents in lookup and revalidate in place. This will be removed once all the users are converted. David Howells noticed that if ->atomic_open() opens the file but does not create it, handle_truncate() will be called on it even if it is not a regular file. Fix this by checking the file type in this case too. Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'Documentation/filesystems/vfs.txt')
-rw-r--r--Documentation/filesystems/vfs.txt11
1 files changed, 11 insertions, 0 deletions
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index efd23f48170..beb6e691f70 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -364,6 +364,9 @@ struct inode_operations {
ssize_t (*listxattr) (struct dentry *, char *, size_t);
int (*removexattr) (struct dentry *, const char *);
void (*update_time)(struct inode *, struct timespec *, int);
+ struct file * (*atomic_open)(struct inode *, struct dentry *,
+ struct opendata *, unsigned open_flag,
+ umode_t create_mode, bool *created);
};
Again, all methods are called without any locks being held, unless
@@ -476,6 +479,14 @@ otherwise noted.
an inode. If this is not defined the VFS will update the inode itself
and call mark_inode_dirty_sync.
+ atomic_open: called on the last component of an open. Using this optional
+ method the filesystem can look up, possibly create and open the file in
+ one atomic operation. If it cannot perform this (e.g. the file type
+ turned out to be wrong) it may signal this by returning NULL instead of
+ an open struct file pointer. This method is only called if the last
+ component is negative or needs lookup. Cached positive dentries are
+ still handled by f_op->open().
+
The Address Space Object
========================