kernel/git/stable/linux.git/fs/super.c, branch linux-5.9.y

vfs: remove lockdep bogosity in __sb_start_write

2020-11-24T12:38:53+00:00

[ Upstream commit 22843291efc986ce7722610073fcf85a39b4cb13 ] __sb_start_write has some weird looking lockdep code that claims to exist to handle nested freeze locking requests from xfs. The code as written seems broken -- if we think we hold a read lock on any of the higher freeze levels (e.g. we hold SB_FREEZE_WRITE and are trying to lock SB_FREEZE_PAGEFAULT), it converts a blocking lock attempt into a trylock. However, it's not correct to downgrade a blocking lock attempt to a trylock unless the downgrading code or the callers are prepared to deal with that situation. Neither __sb_start_write nor its callers handle this at all. For example: sb_start_pagefault ignores the return value completely, with the result that if xfs_filemap_fault loses a race with a different thread trying to fsfreeze, it will proceed without pagefault freeze protection (thereby breaking locking rules) and then unlocks the pagefault freeze lock that it doesn't own on its way out (thereby corrupting the lock state), which leads to a system hang shortly afterwards. Normally, this won't happen because our ownership of a read lock on a higher freeze protection level blocks fsfreeze from grabbing a write lock on that higher level. *However*, if lockdep is offline, lock_is_held_type unconditionally returns 1, which means that percpu_rwsem_is_held returns 1, which means that __sb_start_write unconditionally converts blocking freeze lock attempts into trylocks, even when we *don't* hold anything that would block a fsfreeze. Apparently this all held together until 5.10-rc1, when bugs in lockdep caused lockdep to shut itself off early in an fstests run, and once fstests gets to the "race writes with freezer" tests, kaboom. This might explain the long trail of vanishingly infrequent livelocks in fstests after lockdep goes offline that I've never been able to diagnose. We could fix it by spinning on the trylock if wait==true, but AFAICT the locking works fine if lockdep is not built at all (and I didn't see any complaints running fstests overnight), so remove this snippet entirely. NOTE: Commit f4b554af9931 in 2015 created the current weird logic (which used to exist in a different form in commit 5accdf82ba25c from 2012) in __sb_start_write. XFS solved this whole problem in the late 2.6 era by creating a variant of transactions (XFS_TRANS_NO_WRITECOUNT) that don't grab intwrite freeze protection, thus making lockdep's solution unnecessary. The commit claims that Dave Chinner explained that the trylock hack + comment could be removed, but nobody ever did. Signed-off-by: Darrick J. Wong Reviewed-by: Christoph Hellwig Reviewed-by: Jan Kara Signed-off-by: Sasha Levin

Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2020-06-10T23:09:11+00:00

Pull vfs fixes from Al Viro: "A couple of trivial patches that fell through the cracks last cycle" * 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: fs: fix indentation in deactivate_super() vfs: Remove duplicated d_mountpoint check in __is_local_mountpoint

Merge tag 'for-5.8/block-2020-06-01' of git://git.kernel.dk/linux-block

2020-06-02T22:29:19+00:00

Pull block updates from Jens Axboe: "Core block changes that have been queued up for this release: - Remove dead blk-throttle and blk-wbt code (Guoqing) - Include pid in blktrace note traces (Jan) - Don't spew I/O errors on wouldblock termination (me) - Zone append addition (Johannes, Keith, Damien) - IO accounting improvements (Konstantin, Christoph) - blk-mq hardware map update improvements (Ming) - Scheduler dispatch improvement (Salman) - Inline block encryption support (Satya) - Request map fixes and improvements (Weiping) - blk-iocost tweaks (Tejun) - Fix for timeout failing with error injection (Keith) - Queue re-run fixes (Douglas) - CPU hotplug improvements (Christoph) - Queue entry/exit improvements (Christoph) - Move DMA drain handling to the few drivers that use it (Christoph) - Partition handling cleanups (Christoph)" * tag 'for-5.8/block-2020-06-01' of git://git.kernel.dk/linux-block: (127 commits) block: mark bio_wouldblock_error() bio with BIO_QUIET blk-wbt: rename __wbt_update_limits to wbt_update_limits blk-wbt: remove wbt_update_limits blk-throttle: remove tg_drain_bios blk-throttle: remove blk_throtl_drain null_blk: force complete for timeout request blk-mq: drain I/O when all CPUs in a hctx are offline blk-mq: add blk_mq_all_tag_iter blk-mq: open code __blk_mq_alloc_request in blk_mq_alloc_request_hctx blk-mq: use BLK_MQ_NO_TAG in more places blk-mq: rename BLK_MQ_TAG_FAIL to BLK_MQ_NO_TAG blk-mq: move more request initialization to blk_mq_rq_ctx_init blk-mq: simplify the blk_mq_get_request calling convention blk-mq: remove the bio argument to ->prepare_request nvme: force complete cancelled requests blk-mq: blk-mq: provide forced completion method block: fix a warning when blkdev.h is included for !CONFIG_BLOCK builds block: blk-crypto-fallback: remove redundant initialization of variable err block: reduce part_stat_lock() scope block: use __this_cpu_add() instead of access by smp_processor_id() ...

fs: fix indentation in deactivate_super()

2020-05-29T14:35:25+00:00

Fix the breaked indent in deactive_super(). Signed-off-by: Yufen Yu Signed-off-by: Al Viro

bdi: remove the name field in struct backing_dev_info

2020-05-09T22:15:13+00:00

The name is only printed for a not registered bdi in writeback. Use the device name there as is more useful anyway for the unlike case that the warning triggers. Signed-off-by: Christoph Hellwig Reviewed-by: Jan Kara Reviewed-by: Greg Kroah-Hartman Reviewed-by: Bart Van Assche Signed-off-by: Jens Axboe

bdi: simplify bdi_alloc

2020-05-09T22:15:13+00:00

Merge the _node vs normal version and drop the superflous gfp_t argument. Signed-off-by: Christoph Hellwig Reviewed-by: Jan Kara Reviewed-by: Greg Kroah-Hartman Reviewed-by: Bart Van Assche Signed-off-by: Jens Axboe

Fix use after free in get_tree_bdev()

2020-04-28T21:37:40+00:00

Commit 6fcf0c72e4b9, a fix to get_tree_bdev() put a missing blkdev_put() in the wrong place, before a warnf() that displays the bdev under consideration rather after it. This results in a silent lockup in printk("%pg") called via warnf() from get_tree_bdev() under some circumstances when there's a race with the blockdev being frozen. This can be caused by xfstests/tests/generic/085 in combination with Lukas Czerner's ext4 mount API conversion patchset. It looks like it ought to occur with other users of get_tree_bdev() such as XFS, but apparently doesn't. Fix this by switching the order of the lines. Fixes: 6fcf0c72e4b9 ("vfs: add missing blkdev_put() in get_tree_bdev()") Reported-by: Lukas Czerner Signed-off-by: David Howells cc: Ian Kent cc: Al Viro Signed-off-by: Linus Torvalds

fs: call fsnotify_sb_delete after evict_inodes

2019-12-18T05:03:01+00:00

When a filesystem is unmounted, we currently call fsnotify_sb_delete() before evict_inodes(), which means that fsnotify_unmount_inodes() must iterate over all inodes on the superblock looking for any inodes with watches. This is inefficient and can lead to livelocks as it iterates over many unwatched inodes. At this point, SB_ACTIVE is gone and dropping refcount to zero kicks the inode out out immediately, so anything processed by fsnotify_sb_delete / fsnotify_unmount_inodes gets evicted in that loop. After that, the call to evict_inodes will evict everything else with a zero refcount. This should speed things up overall, and avoid livelocks in fsnotify_unmount_inodes(). Signed-off-by: Eric Sandeen Reviewed-by: Jan Kara Signed-off-by: Al Viro

Merge branch 'work.mount3' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2019-10-10T15:16:44+00:00

Pull mount fixes from Al Viro: "A couple of regressions from the mount series" * 'work.mount3' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: vfs: add missing blkdev_put() in get_tree_bdev() shmem: fix LSM options parsing

vfs: add missing blkdev_put() in get_tree_bdev()

2019-10-10T02:53:57+00:00

Is there are a couple of missing blkdev_put() in get_tree_bdev()? Signed-off-by: Al Viro