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author | John Muir <john@jmuir.com> | 2011-12-06 21:50:06 +0100 |
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committer | Miklos Szeredi <mszeredi@suse.cz> | 2011-12-13 11:58:49 +0100 |
commit | 451d0f599934fd97faf54a5d7954b518e66192cb (patch) | |
tree | 6dd7a6fcdc8ff3bc50dec37b114c447b3b1d7ba1 /mm/sparse-vmemmap.c | |
parent | b18da0c56e9ff43a007b6c8e302c62e720964151 (diff) | |
download | linux-451d0f599934fd97faf54a5d7954b518e66192cb.tar.bz2 |
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 'mm/sparse-vmemmap.c')
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