linux/include
John Muir 451d0f5999 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>
2011-12-13 11:58:49 +01:00
..
acpi Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux 2011-11-07 10:13:52 -08:00
asm-generic asm-generic/unistd.h: support new process_vm_{readv,write} syscalls 2011-12-03 15:31:48 -05:00
crypto crypto: Add a report function pointer to crypto_type 2011-10-21 14:24:03 +02:00
drm drm/radeon/kms: add some new pci ids 2011-12-01 16:34:15 +00:00
keys encrypted-keys: add key format support 2011-06-27 09:10:45 -04:00
linux FUSE: Notifying the kernel of deletion. 2011-12-13 11:58:49 +01:00
math-emu
media Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
misc [media] altera-stapl: it is time to move out from staging 2011-09-23 15:00:57 -03:00
mtd mtd: kill old field for `struct mtd_info_user' 2011-09-11 15:57:44 +03:00
net sch_red: fix red_calc_qavg_from_idle_time 2011-11-30 23:27:22 -05:00
pcmcia pcmcia: add PCMCIA_DEVICE_MANF_CARD_PROD_ID3 2011-08-08 16:04:11 -04:00
rdma Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/roland/infiniband 2011-11-01 10:51:38 -07:00
rxrpc atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
scsi Merge git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi-misc-2.6 2011-10-28 16:44:18 -07:00
sound Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
target target: remove the unused se_dev_list 2011-12-06 06:00:57 +00:00
trace Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
video ARM: OMAP: HWMOD: Unify DSS resets for OMAPs 2011-11-08 03:16:13 -07:00
xen xen: Remove hanging references to CONFIG_XEN_PLATFORM_PCI 2011-11-16 12:13:42 -05:00
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