From 451d0f599934fd97faf54a5d7954b518e66192cb Mon Sep 17 00:00:00 2001 From: John Muir Date: Tue, 6 Dec 2011 21:50:06 +0100 Subject: 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 Signed-off-by: Miklos Szeredi --- include/linux/fuse.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'include/linux/fuse.h') 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; -- cgit v1.2.1