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2008-11-23ext4: Fix lockdep recursive locking warningAneesh Kumar K.V
In ext4_mb_init_group(), if the filesystem block size is less than PAGE_SIZE/2, the code tries to grab alloc_sem for multiple block groups in a loop. We need to allow for this by using down_write_nested() and passing in the loop index as a lock subclass number. This works because no other code path needs to take multiple alloc_sem's. Note that lockdep will fail for filesystem blocksize smaller than to PAGE_SIZE/16k. (e.g., a 1k filesystem blocksize with a 32k page size, or a 2k filesystem blocksize with a 64k blocksize, etc.) Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
2009-01-05ext4: don't use blocks freed but not yet committed in buddy cache initAneesh Kumar K.V
When we generate buddy cache (especially during resize) we need to make sure we don't use the blocks freed but not yet comitted. This makes sure we have the right value of free blocks count in the group info and also in the bitmap. This also ensures the ordered mode consistency Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Cc: stable@kernel.org
2008-11-23vfs, seqfile: fix comment style on mangle_pathTörök Edwin
Impact: use standard docbook tags Reported-by: Randy Dunlap <randy.dunlap@oracle.com> Signed-off-by: Török Edwin <edwintorok@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-23vfs, seqfile: make mangle_path() globalTörök Edwin
Impact: expose new VFS API make mangle_path() available, as per the suggestions of Christoph Hellwig and Al Viro: http://lkml.org/lkml/2008/11/4/338 Signed-off-by: Török Edwin <edwintorok@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-11-21UBIFS: pre-allocate bulk-read bufferArtem Bityutskiy
To avoid memory allocation failure during bulk-read, pre-allocate a bulk-read buffer, so that if there is only one bulk-reader at a time, it would just use the pre-allocated buffer and would not do any memory allocation. However, if there are more than 1 bulk- reader, then only one reader would use the pre-allocated buffer, while the other reader would allocate the buffer for itself. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2008-11-21UBIFS: do not allocate too muchArtem Bityutskiy
Bulk-read allocates 128KiB or more using kmalloc. The allocation starts failing often when the memory gets fragmented. UBIFS still works fine in this case, because it falls-back to standard (non-optimized) read method, though. This patch teaches bulk-read to allocate exactly the amount of memory it needs, instead of allocating 128KiB every time. This patch is also a preparation to the further fix where we'll have a pre-allocated bulk-read buffer as well. For example, now the @bu object is prepared in 'ubifs_bulk_read()', so we could path either pre-allocated or allocated information to 'ubifs_do_bulk_read()' later. Or teaching 'ubifs_do_bulk_read()' not to allocate 'bu->buf' if it is already there. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2008-11-21UBIFS: do not print scary memory allocation warningsArtem Bityutskiy
Bulk-read allocates a lot of memory with 'kmalloc()', and when it is/gets fragmented 'kmalloc()' fails with a scarry warning. But because bulk-read is just an optimization, UBIFS keeps working fine. Supress the warning by passing __GFP_NOWARN option to 'kmalloc()'. This patch also introduces a macro for the magic 128KiB constant. This is just neater. Note, this is not really fixes the problem we had, but just hides the warnings. The further patches fix the problem. Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
2008-11-20Merge branch 'master' of ↵David S. Miller
master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 Conflicts: drivers/net/ixgbe/ixgbe_main.c include/net/mac80211.h net/phonet/af_phonet.c
2008-11-20Merge git://git.kernel.org/pub/scm/linux/kernel/git/sfrench/cifs-2.6Linus Torvalds
* git://git.kernel.org/pub/scm/linux/kernel/git/sfrench/cifs-2.6: [CIFS] Do not attempt to close invalidated file handles [CIFS] fix check for dead tcon in smb_init
2008-11-20[CIFS] Do not attempt to close invalidated file handlesSteve French
If a connection with open file handles has gone down and come back up and reconnected without reopening the file handle yet, do not attempt to send an SMB close request for this handle in cifs_close. We were checking for the connection being invalid in cifs_close but since the connection may have been reconnected we also need to check whether the file handle was marked invalid (otherwise we could close the wrong file handle by accident). Acked-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Steve French <sfrench@us.ibm.com>
2008-11-20Btrfs: Fix for lockdep warnings with alloc_mutex and pinned_mutexJosef Bacik
This the lockdep complaint by having a different mutex to gaurd caching the block group, so you don't end up with this backwards dependancy. Thank you, Signed-off-by: Josef Bacik <jbacik@redhat.com>
2008-11-20Btrfs: only flush down bios for writeback pagesChris Mason
The btrfs write_cache_pages call has a flush function so that it submits the bio it has been building before it waits on any writeback pages. This adds a check so that flush only happens on writeback pages. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-11-20Btrfs: Drop dirty roots created by log replay immediately whenYan Zheng
The log replay produces dirty roots. These dirty roots should be dropped immediately if the fs is mounted as ro. Otherwise they can be added to the dirty root list again when remounting the fs as rw. Thank you, Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
2008-11-20Btrfs: compat code fixesChris Mason
The btrfs git kernel trees is used to build a standalone tree for compiling against older kernels. This commit makes the standalone tree work with 2.6.27 Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-11-19Btrfs: Use current_fsuid/gidChris Mason
This fixes compile problems with linux-next Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-11-19hostfs: fix a duplicated global function nameWANG Cong
fs/hostfs/hostfs_user.c defines do_readlink() as non-static, and so does fs/xfs/linux-2.6/xfs_ioctl.c when CONFIG_XFS_DEBUG=y. So rename do_readlink() in hostfs to hostfs_do_readlink(). I think it's better if XFS guys will also rename their do_readlink(), it's not necessary to use such a general name. Signed-off-by: WANG Cong <wangcong@zeuux.org> Cc: Jeff Dike <jdike@addtoit.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-11-19don't unlink an active swapfileHugh Dickins
Peter Cordes is sorry that he rm'ed his swapfiles while they were in use, he then had no pathname to swapoff. It's a curious little oversight, but not one worth a lot of hackery. Kudos to Willy Tarreau for turning this around from a discussion of synthetic pathnames to how to prevent unlink. Mimic immutable: prohibit unlinking an active swapfile in may_delete() (and don't worry my little head over the tiny race window). Signed-off-by: Hugh Dickins <hugh@veritas.com> Cc: Willy Tarreau <w@1wt.eu> Acked-by: Christoph Hellwig <hch@infradead.org> Cc: Peter Cordes <peter@cordes.ca> Cc: Bodo Eggert <7eggert@gmx.de> Cc: David Newall <davidn@davidnewall.com> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-11-19eCryptfs: Allocate up to two scatterlists for crypto ops on keysMichael Halcrow
I have received some reports of out-of-memory errors on some older AMD architectures. These errors are what I would expect to see if crypt_stat->key were split between two separate pages. eCryptfs should not assume that any of the memory sent through virt_to_scatterlist() is all contained in a single page, and so this patch allocates two scatterlist structs instead of one when processing keys. I have received confirmation from one person affected by this bug that this patch resolves the issue for him, and so I am submitting it for inclusion in a future stable release. Note that virt_to_scatterlist() runs sg_init_table() on the scatterlist structs passed to it, so the calls to sg_init_table() in decrypt_passphrase_encrypted_session_key() are redundant. Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com> Reported-by: Paulo J. S. Silva <pjssilva@ime.usp.br> Cc: "Leon Woestenberg" <leon.woestenberg@gmail.com> Cc: Tim Gardner <tim.gardner@canonical.com> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-11-19Btrfs: Fixes for 2.6.28-rc API changesChris Mason
* open/close_bdev_excl -> open/close_bdev_exclusive * blkdev_issue_discard takes a GFP mask now * Fix blkdev_issue_discard usage now that it is enabled Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-11-20nfsctl: add headers for credentialsRandy Dunlap
Needs headers help for current_cred: Adding only cred.h wasn't enough. linux-next-20081023/fs/nfsctl.c:45: error: implicit declaration of function 'current_cred' Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Cc: David Howells <dhowells@redhat.com> Cc: James Morris <jmorris@namei.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: James Morris <jmorris@namei.org>
2008-11-20coda: fix creds referenceRandy Dunlap
Needs a header file for credentials struct: linux-next-20081023/fs/coda/file.c:177: error: dereferencing pointer to incomplete type Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com> Cc: Jan Harkes <jaharkes@cs.cmu.edu> Cc: David Howells <dhowells@redhat.com> Cc: James Morris <jmorris@namei.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: James Morris <jmorris@namei.org>
2008-11-19Merge branch 'master' of ↵Chris Mason
git://git.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-unstable
2008-11-19Btrfs: fix free space accounting when unpinning extentsJosef Bacik
This patch fixes what I hope is the last early ENOSPC bug left. I did not know that pinned extents would merge into one big extent when inserted on to the pinned extent tree, so I was adding free space to a block group that could possibly span multiple block groups. This is a big issue because first that space doesn't exist in that block group, and second we won't actually use that space because there are a bunch of other checks to make sure we're allocating within the constraints of the block group. This patch fixes the problem by adding the btrfs_add_free_space to btrfs_update_pinned_extents which makes sure we are adding the appropriate amount of free space to the appropriate block group. Thanks much to Lee Trager for running my myriad of debug patches to help me track this problem down. Thank you, Signed-off-by: Josef Bacik <jbacik@redhat.com>
2008-11-19Btrfs: Do fsync log replay when mount -o ro, except when on readonly mediaChris Mason
fsync log replay can change the filesystem, so it cannot be delayed until mount -o rw,remount, and it can't be forgotten entirely. So, this patch changes btrfs to do with reiserfs, ext3 and xfs do, which is to do the log replay even when mounted readonly. On a readonly device if log replay is required, the mount is aborted. Getting all of this right had required fixing up some of the error handling in open_ctree. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-11-19Btrfs: Avoid writeback stallsChris Mason
While building large bios in writepages, btrfs may end up waiting for other page writeback to finish if WB_SYNC_ALL is used. While it is waiting, the bio it is building has a number of pages with the writeback bit set and they aren't getting to the disk any time soon. This lowers the latencies of writeback in general by sending down the bio being built before waiting for other pages. The bio submission code tries to limit the total number of async bios in flight by waiting when we're over a certain number of async bios. But, the waits are happening while writepages is building bios, and this can easily lead to stalls and other problems for people calling wait_on_page_writeback. The current fix is to let the congestion tests take care of waiting. sync() and others make sure to drain the current async requests to make sure that everything that was pending when the sync was started really get to disk. The code would drain pending requests both before and after submitting a new request. But, if one of the requests is waiting for page writeback to finish, the draining waits might block that page writeback. This changes the draining code to only wait after submitting the bio being processed. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-11-18Merge branch 'master' of ↵David S. Miller
master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6 Conflicts: drivers/isdn/i4l/isdn_net.c fs/cifs/connect.c
2008-11-18Btrfs: switch back to wait_on_page_writeback to wait on metadata writesChris Mason
The extent based waiting was using more CPU, and other fixes have helped with the unplug storm problems. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-11-18Btrfs: Update the disk format for the seed device and new root codeChris Mason
Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-11-18[CIFS] fix check for dead tcon in smb_initSteve French
This was recently changed to check for need_reconnect, but should actually be a check for a tidStatus of CifsExiting. Signed-off-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Steve French <sfrench@us.ibm.com>
2008-11-18Btrfs: unplug all devices in the unplug call backChris Mason
For larger multi-device filesystems, there was logic to limit the number of devices unplugged to just the page that was sent to our sync_page function. But, the code wasn't always unplugging the right device. Since this was just an optimization, disable it for now. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-11-18Btrfs: Some fixes for batching extent insert.Liu Hui
In insert_extents(), when ret==1 and last is not zero, it should check if the current inserted item is the last item in this batching inserts. If so, it should just break from loop. If not, 'cur = insert_list->next' will make no sense because the list is empty now, and 'op' will point to an unexpectable place. There are also some trivial fixs in this patch including one comment typo error and deleting two redundant lines. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-11-18block/md: fix md autodetectionTejun Heo
Block ext devt conversion missed md_autodetect_dev() call in rescan_partitions() leaving md autodetect unable to see partitions. Fix it. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Neil Brown <neilb@suse.de> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-11-18block: make add_partition() return pointer to hd_structTejun Heo
Make add_partition() return pointer to the new hd_struct on success and ERR_PTR() value on failure. This change will be used to fix md autodetection bug. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Neil Brown <neilb@suse.de> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-11-18block: fix add_partition() error pathTejun Heo
Partition stats structure was not freed on devt allocation failure path. Fix it. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2008-11-18Merge branch 'master' into nextJames Morris
Conflicts: fs/cifs/misc.c Merge to resolve above, per the patch below. Signed-off-by: James Morris <jmorris@namei.org> diff --cc fs/cifs/misc.c index ec36410,addd1dc..0000000 --- a/fs/cifs/misc.c +++ b/fs/cifs/misc.c @@@ -347,13 -338,13 +338,13 @@@ header_assemble(struct smb_hdr *buffer /* BB Add support for establishing new tCon and SMB Session */ /* with userid/password pairs found on the smb session */ /* for other target tcp/ip addresses BB */ - if (current->fsuid != treeCon->ses->linux_uid) { + if (current_fsuid() != treeCon->ses->linux_uid) { cFYI(1, ("Multiuser mode and UID " "did not match tcon uid")); - read_lock(&GlobalSMBSeslock); - list_for_each(temp_item, &GlobalSMBSessionList) { - ses = list_entry(temp_item, struct cifsSesInfo, cifsSessionList); + read_lock(&cifs_tcp_ses_lock); + list_for_each(temp_item, &treeCon->ses->server->smb_ses_list) { + ses = list_entry(temp_item, struct cifsSesInfo, smb_ses_list); - if (ses->linux_uid == current->fsuid) { + if (ses->linux_uid == current_fsuid()) { if (ses->server == treeCon->ses->server) { cFYI(1, ("found matching uid substitute right smb_uid")); buffer->Uid = ses->Suid;
2008-11-17Merge git://git.kernel.org/pub/scm/linux/kernel/git/sfrench/cifs-2.6Linus Torvalds
* git://git.kernel.org/pub/scm/linux/kernel/git/sfrench/cifs-2.6: prevent cifs_writepages() from skipping unwritten pages Fixed parsing of mount options when doing DFS submount [CIFS] Fix check for tcon seal setting and fix oops on failed mount from earlier patch [CIFS] Fix build break cifs: reinstate sharing of tree connections [CIFS] minor cleanup to cifs_mount cifs: reinstate sharing of SMB sessions sans races cifs: disable sharing session and tcon and add new TCP sharing code [CIFS] clean up server protocol handling [CIFS] remove unused list, add new cifs sock list to prepare for mount/umount fix [CIFS] Fix cifs reconnection flags [CIFS] Can't rely on iov length and base when kernel_recvmsg returns error
2008-11-18prevent cifs_writepages() from skipping unwritten pagesDave Kleikamp
Fixes a data corruption under heavy stress in which pages could be left dirty after all open instances of a inode have been closed. In order to write contiguous pages whenever possible, cifs_writepages() asks pagevec_lookup_tag() for more pages than it may write at one time. Normally, it then resets index just past the last page written before calling pagevec_lookup_tag() again. If cifs_writepages() can't write the first page returned, it wasn't resetting index, and the next call to pagevec_lookup_tag() resulted in skipping all of the pages it previously returned, even though cifs_writepages() did nothing with them. This can result in data loss when the file descriptor is about to be closed. This patch ensures that index gets set back to the next returned page so that none get skipped. Signed-off-by: Dave Kleikamp <shaggy@linux.vnet.ibm.com> Acked-by: Jeff Layton <jlayton@redhat.com> Cc: Shirish S Pargaonkar <shirishp@us.ibm.com> Signed-off-by: Steve French <sfrench@us.ibm.com>
2008-11-18Fixed parsing of mount options when doing DFS submountIgor Mammedov
Since these hit the same routines, and are relatively small, it is easier to review them as one patch. Fixed incorrect handling of the last option in some cases Fixed prefixpath handling convert path_consumed into host depended string length (in bytes) Use non default separator if it is provided in the original mount options Acked-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Igor Mammedov <niallain@gmail.com> Signed-off-by: Steve French <sfrench@us.ibm.com>
2008-11-17Btrfs: prevent loops in the directory tree when creating snapshotsChris Mason
For a directory tree: /mnt/subvolA/subvolB btrfsctl -s /mnt/subvolA/subvolB /mnt Will create a directory loop with subvolA under subvolB. This commit uses the forward refs for each subvol and snapshot to error out before creating the loop. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-11-17Btrfs: Add backrefs and forward refs for subvols and snapshotsChris Mason
Subvols and snapshots can now be referenced from any point in the directory tree. We need to maintain back refs for them so we can find lost subvols. Forward refs are added so that we know all of the subvols and snapshots referenced anywhere in the directory tree of a single subvol. This can be used to do recursive snapshotting (but they aren't yet) and it is also used to detect and prevent directory loops when creating new snapshots. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-11-17Btrfs: Give each subvol and snapshot their own anonymous devidChris Mason
Each subvolume has its own private inode number space, and so we need to fill in different device numbers for each subvolume to avoid confusing applications. This commit puts a struct super_block into struct btrfs_root so it can call set_anon_super() and get a different device number generated for each root. btrfs_rename is changed to prevent renames across subvols. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-11-17Btrfs: Allow subvolumes and snapshots anywhere in the directory treeChris Mason
Before, all snapshots and subvolumes lived in a single flat directory. This was awkward and confusing because the single flat directory was only writable with the ioctls. This commit changes the ioctls to create subvols and snapshots at any point in the directory tree. This requires making separate ioctls for snapshot and subvol creation instead of a combining them into one. The subvol ioctl does: btrfsctl -S subvol_name parent_dir After the ioctl is done subvol_name lives inside parent_dir. The snapshot ioctl does: btrfsctl -s path_for_snapshot root_to_snapshot path_for_snapshot can be an absolute or relative path. btrfsctl breaks it up into directory and basename components. root_to_snapshot can be any file or directory in the FS. The snapshot is taken of the entire root where that file lives. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-11-17Btrfs: Add some debugging around the ENOSPC bugsJosef Bacik
Some people are still reporting problems with early enospc. This will help narrown down the cause. Signed-off-by: Chris Mason <chris.mason@oracle.com>
2008-11-17Btrfs: fix free space leakJosef Bacik
In my batch delete/update/insert patch I introduced a free space leak. The extent that we do the original search on in free_extents is never pinned, so we always update the block saying that it has free space, but the free space never actually gets added to the free space tree, since op->del will always be 0 and it's never actually added to the pinned extents tree. This patch fixes this problem by making sure we call pin_down_bytes on the pending extent op and set op->del to the return value of pin_down_bytes so update_block_group is called with the right value. This seems to fix the case where we were getting ENOSPC when there was plenty of space available. Signed-off-by: Josef Bacik <jbacik@redhat.com>
2008-11-17[CIFS] Fix check for tcon seal setting and fix oops on failed mount from ↵Steve French
earlier patch set tcon->ses earlier If the inital tree connect fails, we'll end up calling cifs_put_smb_ses with a NULL pointer. Fix it by setting the tcon->ses earlier. Acked-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Steve French <sfrench@us.ibm.com>
2008-11-17[XFS] Fix double free of log ticketsDave Chinner
When an I/O error occurs during an intermediate commit on a rolling transaction, xfs_trans_commit() will free the transaction structure and the related ticket. However, the duplicate transaction that gets used as the transaction continues still contains a pointer to the ticket. Hence when the duplicate transaction is cancelled and freed, we free the ticket a second time. Add reference counting to the ticket so that we hold an extra reference to the ticket over the transaction commit. We drop the extra reference once we have checked that the transaction commit did not return an error, thus avoiding a double free on commit error. Credit to Nick Piggin for tripping over the problem. SGI-PV: 989741 Signed-off-by: Dave Chinner <david@fromorbit.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
2008-11-17[CIFS] Fix build breakSteve French
Signed-off-by: Steve French <sfrench@us.ibm.com>
2008-11-17cifs: reinstate sharing of tree connectionsJeff Layton
Use a similar approach to the SMB session sharing. Add a list of tcons attached to each SMB session. Move the refcount to non-atomic. Protect all of the above with the cifs_tcp_ses_lock. Add functions to properly find and put references to the tcons. Signed-off-by: Jeff Layton <jlayton@redhat.com> Signed-off-by: Steve French <sfrench@us.ibm.com>
2008-11-16Fix broken ownership of /proc/sys/ filesAl Viro
D'oh... Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Reported-and-tested-by: Peter Palfrader <peter@palfrader.org> Cc: stable@kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-11-15Fix inotify watch removal/umount racesAl Viro
Inotify watch removals suck violently. To kick the watch out we need (in this order) inode->inotify_mutex and ih->mutex. That's fine if we have a hold on inode; however, for all other cases we need to make damn sure we don't race with umount. We can *NOT* just grab a reference to a watch - inotify_unmount_inodes() will happily sail past it and we'll end with reference to inode potentially outliving its superblock. Ideally we just want to grab an active reference to superblock if we can; that will make sure we won't go into inotify_umount_inodes() until we are done. Cleanup is just deactivate_super(). However, that leaves a messy case - what if we *are* racing with umount() and active references to superblock can't be acquired anymore? We can bump ->s_count, grab ->s_umount, which will almost certainly wait until the superblock is shut down and the watch in question is pining for fjords. That's fine, but there is a problem - we might have hit the window between ->s_active getting to 0 / ->s_count - below S_BIAS (i.e. the moment when superblock is past the point of no return and is heading for shutdown) and the moment when deactivate_super() acquires ->s_umount. We could just do drop_super() yield() and retry, but that's rather antisocial and this stuff is luser-triggerable. OTOH, having grabbed ->s_umount and having found that we'd got there first (i.e. that ->s_root is non-NULL) we know that we won't race with inotify_umount_inodes(). So we could grab a reference to watch and do the rest as above, just with drop_super() instead of deactivate_super(), right? Wrong. We had to drop ih->mutex before we could grab ->s_umount. So the watch could've been gone already. That still can be dealt with - we need to save watch->wd, do idr_find() and compare its result with our pointer. If they match, we either have the damn thing still alive or we'd lost not one but two races at once, the watch had been killed and a new one got created with the same ->wd at the same address. That couldn't have happened in inotify_destroy(), but inotify_rm_wd() could run into that. Still, "new one got created" is not a problem - we have every right to kill it or leave it alone, whatever's more convenient. So we can use idr_find(...) == watch && watch->inode->i_sb == sb as "grab it and kill it" check. If it's been our original watch, we are fine, if it's a newcomer - nevermind, just pretend that we'd won the race and kill the fscker anyway; we are safe since we know that its superblock won't be going away. And yes, this is far beyond mere "not very pretty"; so's the entire concept of inotify to start with. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Acked-by: Greg KH <greg@kroah.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>