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authorJohn Muir <john@jmuir.com>2011-12-07 00:50:06 +0400
committerMiklos Szeredi <mszeredi@suse.cz>2011-12-13 14:58:49 +0400
commit451d0f599934fd97faf54a5d7954b518e66192cb (patch)
tree6dd7a6fcdc8ff3bc50dec37b114c447b3b1d7ba1 /fs/fuse/fuse_i.h
parentb18da0c56e9ff43a007b6c8e302c62e720964151 (diff)
downloadlinux-451d0f599934fd97faf54a5d7954b518e66192cb.tar.xz
FUSE: Notifying the kernel of deletion.
Allows a FUSE file-system to tell the kernel when a file or directory is deleted. If the specified dentry has the specified inode number, the kernel will unhash it. The current 'fuse_notify_inval_entry' does not cause the kernel to clean up directories that are in use properly, and as a result the users of those directories see incorrect semantics from the file-system. The error condition seen when 'fuse_notify_inval_entry' is used to notify of a deleted directory is avoided when 'fuse_notify_delete' is used instead. The following scenario demonstrates the difference: 1. User A chdirs into 'testdir' and starts reading 'testfile'. 2. User B rm -rf 'testdir'. 3. User B creates 'testdir'. 4. User C chdirs into 'testdir'. If you run the above within the same machine on any file-system (including fuse file-systems), there is no problem: user C is able to chdir into the new testdir. The old testdir is removed from the dentry tree, but still open by user A. If operations 2 and 3 are performed via the network such that the fuse file-system uses one of the notify functions to tell the kernel that the nodes are gone, then the following error occurs for user C while user A holds the original directory open: muirj@empacher:~> ls /test/testdir ls: cannot access /test/testdir: No such file or directory The issue here is that the kernel still has a dentry for testdir, and so it is requesting the attributes for the old directory, while the file-system is responding that the directory no longer exists. If on the other hand, if the file-system can notify the kernel that the directory is deleted using the new 'fuse_notify_delete' function, then the above ls will find the new directory as expected. Signed-off-by: John Muir <john@jmuir.com> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Diffstat (limited to 'fs/fuse/fuse_i.h')
-rw-r--r--fs/fuse/fuse_i.h8
1 files changed, 7 insertions, 1 deletions
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 09337bcc2554..a571584a091a 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -755,9 +755,15 @@ int fuse_reverse_inval_inode(struct super_block *sb, u64 nodeid,
/**
* File-system tells the kernel to invalidate parent attributes and
* the dentry matching parent/name.
+ *
+ * If the child_nodeid is non-zero and:
+ * - matches the inode number for the dentry matching parent/name,
+ * - is not a mount point
+ * - is a file or oan empty directory
+ * then the dentry is unhashed (d_delete()).
*/
int fuse_reverse_inval_entry(struct super_block *sb, u64 parent_nodeid,
- struct qstr *name);
+ u64 child_nodeid, struct qstr *name);
int fuse_do_open(struct fuse_conn *fc, u64 nodeid, struct file *file,
bool isdir);