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authorJohn Muir <john@jmuir.com>2011-12-06 21:50:06 +0100
committerMiklos Szeredi <mszeredi@suse.cz>2011-12-13 11:58:49 +0100
commit451d0f599934fd97faf54a5d7954b518e66192cb (patch)
tree6dd7a6fcdc8ff3bc50dec37b114c447b3b1d7ba1 /include/linux/fuse.h
parentb18da0c56e9ff43a007b6c8e302c62e720964151 (diff)
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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 'include/linux/fuse.h')
-rw-r--r--include/linux/fuse.h9
1 files changed, 9 insertions, 0 deletions
diff --git a/include/linux/fuse.h b/include/linux/fuse.h
index 446c89718b9c..8ba2c9460b28 100644
--- a/include/linux/fuse.h
+++ b/include/linux/fuse.h
@@ -53,6 +53,7 @@
*
* 7.18
* - add FUSE_IOCTL_DIR flag
+ * - add FUSE_NOTIFY_DELETE
*/
#ifndef _LINUX_FUSE_H
@@ -288,6 +289,7 @@ enum fuse_notify_code {
FUSE_NOTIFY_INVAL_ENTRY = 3,
FUSE_NOTIFY_STORE = 4,
FUSE_NOTIFY_RETRIEVE = 5,
+ FUSE_NOTIFY_DELETE = 6,
FUSE_NOTIFY_CODE_MAX,
};
@@ -611,6 +613,13 @@ struct fuse_notify_inval_entry_out {
__u32 padding;
};
+struct fuse_notify_delete_out {
+ __u64 parent;
+ __u64 child;
+ __u32 namelen;
+ __u32 padding;
+};
+
struct fuse_notify_store_out {
__u64 nodeid;
__u64 offset;