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2022-06-14fs-writeback: writeback_sb_inodes：Recalculate 'wrote' according skipped pagesZhihao Cheng1-5/+8
commit 68f4c6eba70df70a720188bce95c85570ddfcc87 upstream. Commit 505a666ee3fc ("writeback: plug writeback in wb_writeback() and writeback_inodes_wb()") has us holding a plug during wb_writeback, which may cause a potential ABBA dead lock: wb_writeback fat_file_fsync blk_start_plug(&plug) for (;;) { iter i-1: some reqs have been added into plug->mq_list // LOCK A iter i: progress = __writeback_inodes_wb(wb, work) . writeback_sb_inodes // fat's bdev . __writeback_single_inode . . generic_writepages . . __block_write_full_page . . . . __generic_file_fsync . . . . sync_inode_metadata . . . . writeback_single_inode . . . . __writeback_single_inode . . . . fat_write_inode . . . . __fat_write_inode . . . . sync_dirty_buffer // fat's bdev . . . . lock_buffer(bh) // LOCK B . . . . submit_bh . . . . blk_mq_get_tag // LOCK A . . . trylock_buffer(bh) // LOCK B . . . redirty_page_for_writepage . . . wbc->pages_skipped++ . . --wbc->nr_to_write . wrote += write_chunk - wbc.nr_to_write // wrote > 0 . requeue_inode . redirty_tail_locked if (progress) // progress > 0 continue; iter i+1: queue_io // similar process with iter i, infinite for-loop ! } blk_finish_plug(&plug) // flush plug won't be called Above process triggers a hungtask like: [ 399.044861] INFO: task bb:2607 blocked for more than 30 seconds. [ 399.046824] Not tainted 5.18.0-rc1-00005-gefae4d9eb6a2-dirty [ 399.051539] task:bb state:D stack: 0 pid: 2607 ppid: 2426 flags:0x00004000 [ 399.051556] Call Trace: [ 399.051570] __schedule+0x480/0x1050 [ 399.051592] schedule+0x92/0x1a0 [ 399.051602] io_schedule+0x22/0x50 [ 399.051613] blk_mq_get_tag+0x1d3/0x3c0 [ 399.051640] __blk_mq_alloc_requests+0x21d/0x3f0 [ 399.051657] blk_mq_submit_bio+0x68d/0xca0 [ 399.051674] __submit_bio+0x1b5/0x2d0 [ 399.051708] submit_bio_noacct+0x34e/0x720 [ 399.051718] submit_bio+0x3b/0x150 [ 399.051725] submit_bh_wbc+0x161/0x230 [ 399.051734] __sync_dirty_buffer+0xd1/0x420 [ 399.051744] sync_dirty_buffer+0x17/0x20 [ 399.051750] __fat_write_inode+0x289/0x310 [ 399.051766] fat_write_inode+0x2a/0xa0 [ 399.051783] __writeback_single_inode+0x53c/0x6f0 [ 399.051795] writeback_single_inode+0x145/0x200 [ 399.051803] sync_inode_metadata+0x45/0x70 [ 399.051856] __generic_file_fsync+0xa3/0x150 [ 399.051880] fat_file_fsync+0x1d/0x80 [ 399.051895] vfs_fsync_range+0x40/0xb0 [ 399.051929] __x64_sys_fsync+0x18/0x30 In my test, 'need_resched()' (which is imported by 590dca3a71 "fs-writeback: unplug before cond_resched in writeback_sb_inodes") in function 'writeback_sb_inodes()' seldom comes true, unless cond_resched() is deleted from write_cache_pages(). Fix it by correcting wrote number according number of skipped pages in writeback_sb_inodes(). Goto Link to find a reproducer. Link: https://bugzilla.kernel.org/show_bug.cgi?id=215837 Cc: stable@vger.kernel.org # v4.3 Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20220510133805.1988292-1-chengzhihao1@huawei.com Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-07-14writeback: fix obtain a reference to a freeing memcg cssMuchun Song1-2/+7
[ Upstream commit 8b0ed8443ae6458786580d36b7d5f8125535c5d4 ] The caller of wb_get_create() should pin the memcg, because wb_get_create() relies on this guarantee. The rcu read lock only can guarantee that the memcg css returned by css_from_id() cannot be released, but the reference of the memcg can be zero. rcu_read_lock() memcg_css = css_from_id() wb_get_create(memcg_css) cgwb_create(memcg_css) // css_get can change the ref counter from 0 back to 1 css_get(memcg_css) rcu_read_unlock() Fix it by holding a reference to the css before calling wb_get_create(). This is not a problem I encountered in the real world. Just the result of a code review. Fixes: 682aa8e1a6a1 ("writeback: implement unlocked_inode_to_wb transaction and use it for stat updates") Link: https://lore.kernel.org/r/20210402091145.80635-1-songmuchun@bytedance.com Signed-off-by: Muchun Song <songmuchun@bytedance.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-07-14writeback, cgroup: increment isw_nr_in_flight before grabbing an inodeRoman Gushchin1-2/+3
[ Upstream commit 8826ee4fe75051f8cbfa5d4a9aa70565938e724c ] isw_nr_in_flight is used to determine whether the inode switch queue should be flushed from the umount path. Currently it's increased after grabbing an inode and even scheduling the switch work. It means the umount path can walk past cleanup_offline_cgwb() with active inode references, which can result in a "Busy inodes after unmount." message and use-after-free issues (with inode->i_sb which gets freed). Fix it by incrementing isw_nr_in_flight before doing anything with the inode and decrementing in the case when switching wasn't scheduled. The problem hasn't yet been seen in the real life and was discovered by Jan Kara by looking into the code. Link: https://lkml.kernel.org/r/20210608230225.2078447-4-guro@fb.com Signed-off-by: Roman Gushchin <guro@fb.com> Suggested-by: Jan Kara <jack@suse.com> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Dave Chinner <dchinner@redhat.com> Cc: Dennis Zhou <dennis@kernel.org> Cc: Tejun Heo <tj@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-07-14block_dump: remove block_dump feature in mark_inode_dirty()zhangyi (F)1-25/+0
[ Upstream commit 12e0613715e1cf305fffafaf0e89d810d9a85cc0 ] block_dump is an old debugging interface, one of it's functions is used to print the information about who write which file on disk. If we enable block_dump through /proc/sys/vm/block_dump and turn on debug log level, we can gather information about write process name, target file name and disk from kernel message. This feature is realized in block_dump___mark_inode_dirty(), it print above information into kernel message directly when marking inode dirty, so it is noisy and can easily trigger log storm. At the same time, get the dentry refcount is also not safe, we found it will lead to deadlock on ext4 file system with data=journal mode. After tracepoints has been introduced into the kernel, we got a tracepoint in __mark_inode_dirty(), which is a better replacement of block_dump___mark_inode_dirty(). The only downside is that it only trace the inode number and not a file name, but it probably doesn't matter because the original printed file name in block_dump is not accurate in some cases, and we can still find it through the inode number and device id. So this patch delete the dirting inode part of block_dump feature. Signed-off-by: zhangyi (F) <yi.zhang@huawei.com> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20210313030146.2882027-2-yi.zhang@huawei.com Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Sasha Levin <sashal@kernel.org>
2021-01-30fs: fix lazytime expiration handling in __writeback_single_inode()Eric Biggers1-11/+13
commit 1e249cb5b7fc09ff216aa5a12f6c302e434e88f9 upstream. When lazytime is enabled and an inode is being written due to its in-memory updated timestamps having expired, either due to a sync() or syncfs() system call or due to dirtytime_expire_interval having elapsed, the VFS needs to inform the filesystem so that the filesystem can copy the inode's timestamps out to the on-disk data structures. This is done by __writeback_single_inode() calling mark_inode_dirty_sync(), which then calls ->dirty_inode(I_DIRTY_SYNC). However, this occurs after __writeback_single_inode() has already cleared the dirty flags from ->i_state. This causes two bugs: - mark_inode_dirty_sync() redirties the inode, causing it to remain dirty. This wastefully causes the inode to be written twice. But more importantly, it breaks cases where sync_filesystem() is expected to clean dirty inodes. This includes the FS_IOC_REMOVE_ENCRYPTION_KEY ioctl (as reported at https://lore.kernel.org/r/20200306004555.GB225345@gmail.com), as well as possibly filesystem freezing (freeze_super()). - Since ->i_state doesn't contain I_DIRTY_TIME when ->dirty_inode() is called from __writeback_single_inode() for lazytime expiration, xfs_fs_dirty_inode() ignores the notification. (XFS only cares about lazytime expirations, and it assumes that i_state will contain I_DIRTY_TIME during those.) Therefore, lazy timestamps aren't persisted by sync(), syncfs(), or dirtytime_expire_interval on XFS. Fix this by moving the call to mark_inode_dirty_sync() to earlier in __writeback_single_inode(), before the dirty flags are cleared from i_state. This makes filesystems be properly notified of the timestamp expiration, and it avoids incorrectly redirtying the inode. This fixes xfstest generic/580 (which tests FS_IOC_REMOVE_ENCRYPTION_KEY) when run on ext4 or f2fs with lazytime enabled. It also fixes the new lazytime xfstest I've proposed, which reproduces the above-mentioned XFS bug (https://lore.kernel.org/r/20210105005818.92978-1-ebiggers@kernel.org). Alternatively, we could call ->dirty_inode(I_DIRTY_SYNC) directly. But due to the introduction of I_SYNC_QUEUED, mark_inode_dirty_sync() is the right thing to do because mark_inode_dirty_sync() now knows not to move the inode to a writeback list if it is currently queued for sync. Fixes: 0ae45f63d4ef ("vfs: add support for a lazytime mount option") Cc: stable@vger.kernel.org Depends-on: 5afced3bf281 ("writeback: Avoid skipping inode writeback") Link: https://lore.kernel.org/r/20210112190253.64307-2-ebiggers@kernel.org Suggested-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-01-30writeback: Drop I_DIRTY_TIME_EXPIREJan Kara1-17/+11
commit 5fcd57505c002efc5823a7355e21f48dd02d5a51 upstream. The only use of I_DIRTY_TIME_EXPIRE is to detect in __writeback_single_inode() that inode got there because flush worker decided it's time to writeback the dirty inode time stamps (either because we are syncing or because of age). However we can detect this directly in __writeback_single_inode() and there's no need for the strange propagation with I_DIRTY_TIME_EXPIRE flag. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jan Kara <jack@suse.cz> Cc: Eric Biggers <ebiggers@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-09-03writeback: Fix sync livelock due to b_dirty_time processingJan Kara1-27/+17
commit f9cae926f35e8230330f28c7b743ad088611a8de upstream. When we are processing writeback for sync(2), move_expired_inodes() didn't set any inode expiry value (older_than_this). This can result in writeback never completing if there's steady stream of inodes added to b_dirty_time list as writeback rechecks dirty lists after each writeback round whether there's more work to be done. Fix the problem by using sync(2) start time is inode expiry value when processing b_dirty_time list similarly as for ordinarily dirtied inodes. This requires some refactoring of older_than_this handling which simplifies the code noticeably as a bonus. Fixes: 0ae45f63d4ef ("vfs: add support for a lazytime mount option") CC: stable@vger.kernel.org Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-09-03writeback: Avoid skipping inode writebackJan Kara1-5/+12
commit 5afced3bf28100d81fb2fe7e98918632a08feaf5 upstream. Inode's i_io_list list head is used to attach inode to several different lists - wb->{b_dirty, b_dirty_time, b_io, b_more_io}. When flush worker prepares a list of inodes to writeback e.g. for sync(2), it moves inodes to b_io list. Thus it is critical for sync(2) data integrity guarantees that inode is not requeued to any other writeback list when inode is queued for processing by flush worker. That's the reason why writeback_single_inode() does not touch i_io_list (unless the inode is completely clean) and why __mark_inode_dirty() does not touch i_io_list if I_SYNC flag is set. However there are two flaws in the current logic: 1) When inode has only I_DIRTY_TIME set but it is already queued in b_io list due to sync(2), concurrent __mark_inode_dirty(inode, I_DIRTY_SYNC) can still move inode back to b_dirty list resulting in skipping writeback of inode time stamps during sync(2). 2) When inode is on b_dirty_time list and writeback_single_inode() races with __mark_inode_dirty() like: writeback_single_inode() __mark_inode_dirty(inode, I_DIRTY_PAGES) inode->i_state |= I_SYNC __writeback_single_inode() inode->i_state |= I_DIRTY_PAGES; if (inode->i_state & I_SYNC) bail if (!(inode->i_state & I_DIRTY_ALL)) - not true so nothing done We end up with I_DIRTY_PAGES inode on b_dirty_time list and thus standard background writeback will not writeback this inode leading to possible dirty throttling stalls etc. (thanks to Martijn Coenen for this analysis). Fix these problems by tracking whether inode is queued in b_io or b_more_io lists in a new I_SYNC_QUEUED flag. When this flag is set, we know flush worker has queued inode and we should not touch i_io_list. On the other hand we also know that once flush worker is done with the inode it will requeue the inode to appropriate dirty list. When I_SYNC_QUEUED is not set, __mark_inode_dirty() can (and must) move inode to appropriate dirty list. Reported-by: Martijn Coenen <maco@android.com> Reviewed-by: Martijn Coenen <maco@android.com> Tested-by: Martijn Coenen <maco@android.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Fixes: 0ae45f63d4ef ("vfs: add support for a lazytime mount option") CC: stable@vger.kernel.org Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-09-03writeback: Protect inode->i_io_list with inode->i_lockJan Kara1-5/+17
commit b35250c0816c7cf7d0a8de92f5fafb6a7508a708 upstream. Currently, operations on inode->i_io_list are protected by wb->list_lock. In the following patches we'll need to maintain consistency between inode->i_state and inode->i_io_list so change the code so that inode->i_lock protects also all inode's i_io_list handling. Reviewed-by: Martijn Coenen <maco@android.com> Reviewed-by: Christoph Hellwig <hch@lst.de> CC: stable@vger.kernel.org # Prerequisite for "writeback: Avoid skipping inode writeback" Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-02-11memcg: fix a crash in wb_workfn when a device disappearsTheodore Ts'o1-1/+1
commit 68f23b89067fdf187763e75a56087550624fdbee upstream. Without memcg, there is a one-to-one mapping between the bdi and bdi_writeback structures. In this world, things are fairly straightforward; the first thing bdi_unregister() does is to shutdown the bdi_writeback structure (or wb), and part of that writeback ensures that no other work queued against the wb, and that the wb is fully drained. With memcg, however, there is a one-to-many relationship between the bdi and bdi_writeback structures; that is, there are multiple wb objects which can all point to a single bdi. There is a refcount which prevents the bdi object from being released (and hence, unregistered). So in theory, the bdi_unregister() *should* only get called once its refcount goes to zero (bdi_put will drop the refcount, and when it is zero, release_bdi gets called, which calls bdi_unregister). Unfortunately, del_gendisk() in block/gen_hd.c never got the memo about the Brave New memcg World, and calls bdi_unregister directly. It does this without informing the file system, or the memcg code, or anything else. This causes the root wb associated with the bdi to be unregistered, but none of the memcg-specific wb's are shutdown. So when one of these wb's are woken up to do delayed work, they try to dereference their wb->bdi->dev to fetch the device name, but unfortunately bdi->dev is now NULL, thanks to the bdi_unregister() called by del_gendisk(). As a result, *boom*. Fortunately, it looks like the rest of the writeback path is perfectly happy with bdi->dev and bdi->owner being NULL, so the simplest fix is to create a bdi_dev_name() function which can handle bdi->dev being NULL. This also allows us to bulletproof the writeback tracepoints to prevent them from dereferencing a NULL pointer and crashing the kernel if one is tracing with memcg's enabled, and an iSCSI device dies or a USB storage stick is pulled. The most common way of triggering this will be hotremoval of a device while writeback with memcg enabled is going on. It was triggering several times a day in a heavily loaded production environment. Google Bug Id: 145475544 Link: https://lore.kernel.org/r/20191227194829.150110-1-tytso@mit.edu Link: http://lkml.kernel.org/r/20191228005211.163952-1-tytso@mit.edu Signed-off-by: Theodore Ts'o <tytso@mit.edu> Cc: Chris Mason <clm@fb.com> Cc: Tejun Heo <tj@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-11-08cgroup,writeback: don't switch wbs immediately on dead wbs if the memcg is deadTejun Heo1-3/+6
cgroup writeback tries to refresh the associated wb immediately if the current wb is dead. This is to avoid keeping issuing IOs on the stale wb after memcg - blkcg association has changed (ie. when blkcg got disabled / enabled higher up in the hierarchy). Unfortunately, the logic gets triggered spuriously on inodes which are associated with dead cgroups. When the logic is triggered on dead cgroups, the attempt fails only after doing quite a bit of work allocating and initializing a new wb. While c3aab9a0bd91 ("mm/filemap.c: don't initiate writeback if mapping has no dirty pages") alleviated the issue significantly as it now only triggers when the inode has dirty pages. However, the condition can still be triggered before the inode is switched to a different cgroup and the logic simply doesn't make sense. Skip the immediate switching if the associated memcg is dying. This is a simplified version of the following two patches: * https://lore.kernel.org/linux-mm/20190513183053.GA73423@dennisz-mbp/ * http://lkml.kernel.org/r/156355839560.2063.5265687291430814589.stgit@buzz Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Fixes: e8a7abf5a5bd ("writeback: disassociate inodes from dying bdi_writebacks") Acked-by: Dennis Zhou <dennis@kernel.org> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-10-15fs/fs-writeback.c: fix kernel-doc warningRandy Dunlap1-1/+1
Fix kernel-doc warning in fs/fs-writeback.c: fs/fs-writeback.c:913: warning: Excess function parameter 'nr_pages' description in 'cgroup_writeback_by_id' Link: http://lkml.kernel.org/r/756645ac-0ce8-d47e-d30a-04d9e4923a4f@infradead.org Fixes: d62241c7a406 ("writeback, memcg: Implement cgroup_writeback_by_id()") Signed-off-by: Randy Dunlap <rdunlap@infradead.org> Cc: Tejun Heo <tj@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-10-08writeback: fix use-after-free in finish_writeback_work()Tejun Heo1-2/+7
finish_writeback_work() reads @done->waitq after decrementing @done->cnt. However, once @done->cnt reaches zero, @done may be freed (from stack) at any moment and @done->waitq can contain something unrelated by the time finish_writeback_work() tries to read it. This led to the following crash. "BUG: kernel NULL pointer dereference, address: 0000000000000002" #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] SMP DEBUG_PAGEALLOC CPU: 40 PID: 555153 Comm: kworker/u98:50 Kdump: loaded Not tainted ... Workqueue: writeback wb_workfn (flush-btrfs-1) RIP: 0010:_raw_spin_lock_irqsave+0x10/0x30 Code: 48 89 d8 5b c3 e8 50 db 6b ff eb f4 0f 1f 40 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 53 9c 5b fa 31 c0 ba 01 00 00 00 <f0> 0f b1 17 75 05 48 89 d8 5b c3 89 c6 e8 fe ca 6b ff eb f2 66 90 RSP: 0018:ffffc90049b27d98 EFLAGS: 00010046 RAX: 0000000000000000 RBX: 0000000000000246 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000003 RDI: 0000000000000002 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001 R10: ffff889fff407600 R11: ffff88ba9395d740 R12: 000000000000e300 R13: 0000000000000003 R14: 0000000000000000 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff88bfdfa00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000002 CR3: 0000000002409005 CR4: 00000000001606e0 Call Trace: __wake_up_common_lock+0x63/0xc0 wb_workfn+0xd2/0x3e0 process_one_work+0x1f5/0x3f0 worker_thread+0x2d/0x3d0 kthread+0x111/0x130 ret_from_fork+0x1f/0x30 Fix it by reading and caching @done->waitq before decrementing @done->cnt. Link: http://lkml.kernel.org/r/20190924010631.GH2233839@devbig004.ftw2.facebook.com Fixes: 5b9cce4c7eb069 ("writeback: Generalize and expose wb_completion") Signed-off-by: Tejun Heo <tj@kernel.org> Debugged-by: Chris Mason <clm@fb.com> Reviewed-by: Jens Axboe <axboe@kernel.dk> Cc: Jan Kara <jack@suse.cz> Cc: <stable@vger.kernel.org> [5.2+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-08-30writeback: add tracepoints for cgroup foreign writebacksTejun Heo1-0/+5
cgroup foreign inode handling has quite a bit of heuristics and internal states which sometimes makes it difficult to understand what's going on. Add tracepoints to improve visibility. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-08-27writeback, memcg: Implement cgroup_writeback_by_id()Tejun Heo1-0/+83
Implement cgroup_writeback_by_id() which initiates cgroup writeback from bdi and memcg IDs. This will be used by memcg foreign inode flushing. v2: Use wb_get_lookup() instead of wb_get_create() to avoid creating spurious wbs. v3: Interpret 0 @nr as 1.25 * nr_dirty to implement best-effort flushing while avoding possible livelocks. Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-08-27writeback: Generalize and expose wb_completionTejun Heo1-33/+14
wb_completion is used to track writeback completions. We want to use it from memcg side for foreign inode flushes. This patch updates it to remember the target waitq instead of assuming bdi->wb_waitq and expose it outside of fs-writeback.c. Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-08-15writeback, cgroup: inode_switch_wbs() shouldn't give up on wb_switch_rwsem ↵Tejun Heo1-12/+5
trylock fail As inode wb switching may make sync(2) miss some inodes, they're synchronized using wb_switch_rwsem so that no wb switching happens while sync(2) is in progress. In addition to synchronizing the actual switching, the rwsem is also used to prevent queueing new switch attempts while sync(2) is in progress. This is to avoid queueing too many instances while the rwsem is held by sync(2). Unfortunately, this is too agressive and can block wb switching for a long time if sync(2) is frequent. The goal is avoiding expolding the number of scheduled switches, not avoiding scheduling anything. Let's use wb_switch_rwsem only for synchronizing the actual switching and sync(2) and use isw_nr_in_flight instead for limiting the maximum number of scheduled switches. The limit is set to 1024 which should be more than enough while still avoiding extreme situations. Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-08-15writeback, cgroup: Adjust WB_FRN_TIME_CUT_DIV to accelerate foreign inode ↵Tejun Heo1-2/+20
switching WB_FRN_TIME_CUT_DIV is used to tell the foreign inode detection logic to ignore short writeback rounds to prevent getting confused by a burst of short writebacks. The parameter is currently 2 meaning that anything smaller than half of the running average writback duration will be ignored. This is unnecessarily aggressive. The detection logic uses 16 history slots and is already reasonably protected against some short bursts confusing it and the current parameter can lead to tens of seconds of missed detection depending on the writeback pattern. Let's change the parameter to 8, so that it only ignores writeback with are smaller than 12.5% of the current running average. v2: Add comment explaining what's going on with the foreign detection parameters. Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-07-10blkcg, writeback: Add wbc->no_cgroup_ownerTejun Heo1-1/+1
When writeback IOs are bounced through async layers, the IOs should only be accounted against the wbc from the original bdi writeback to avoid confusing cgroup inode ownership arbitration. Add wbc->no_cgroup_owner to allow disabling wbc cgroup owner accounting. This will be used make btrfs compression work well with cgroup IO control. v2: Renamed from no_wbc_acct to no_cgroup_owner and added comment as per Jan. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-07-10blkcg, writeback: Rename wbc_account_io() to wbc_account_cgroup_owner()Tejun Heo1-4/+4
wbc_account_io() does a very specific job - try to see which cgroup is actually dirtying an inode and transfer its ownership to the majority dirtier if needed. The name is too generic and confusing. Let's rename it to something more specific. Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-07-10cgroup, blkcg: Prepare some symbols for module and !CONFIG_CGROUP usagesTejun Heo1-0/+3
btrfs is going to use css_put() and wbc helpers to improve cgroup writeback support. Add dummy css_get() definition and export wbc helpers to prepare for module and !CONFIG_CGROUP builds. Reported-by: kbuild test robot <lkp@intel.com> Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-06-15blkcg, writeback: dead memcgs shouldn't contribute to writeback ownership ↵Tejun Heo1-1/+7
arbitration wbc_account_io() collects information on cgroup ownership of writeback pages to determine which cgroup should own the inode. Pages can stay associated with dead memcgs but we want to avoid attributing IOs to dead blkcgs as much as possible as the association is likely to be stale. However, currently, pages associated with dead memcgs contribute to the accounting delaying and/or confusing the arbitration. Fix it by ignoring pages associated with dead memcgs. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-05-21treewide: Add SPDX license identifier for missed filesThomas Gleixner1-0/+1
Add SPDX license identifiers to all files which: - Have no license information of any form - Have EXPORT_.*_SYMBOL_GPL inside which was used in the initial scan/conversion to ignore the file These files fall under the project license, GPL v2 only. The resulting SPDX license identifier is: GPL-2.0-only Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-05-19fs/writeback.c: use rcu_barrier() to wait for inflight wb switches going ↵Jiufei Xue1-3/+8
into workqueue when umount synchronize_rcu() didn't wait for call_rcu() callbacks, so inode wb switch may not go to the workqueue after synchronize_rcu(). Thus previous scheduled switches was not finished even flushing the workqueue, which will cause a NULL pointer dereferenced followed below. VFS: Busy inodes after unmount of vdd. Self-destruct in 5 seconds. Have a nice day... BUG: unable to handle kernel NULL pointer dereference at 0000000000000278 evict+0xb3/0x180 iput+0x1b0/0x230 inode_switch_wbs_work_fn+0x3c0/0x6a0 worker_thread+0x4e/0x490 ? process_one_work+0x410/0x410 kthread+0xe6/0x100 ret_from_fork+0x39/0x50 Replace the synchronize_rcu() call with a rcu_barrier() to wait for all pending callbacks to finish. And inc isw_nr_in_flight after call_rcu() in inode_switch_wbs() to make more sense. Link: http://lkml.kernel.org/r/20190429024108.54150-1-jiufei.xue@linux.alibaba.com Signed-off-by: Jiufei Xue <jiufei.xue@linux.alibaba.com> Acked-by: Tejun Heo <tj@kernel.org> Suggested-by: Tejun Heo <tj@kernel.org> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-23writeback: synchronize sync(2) against cgroup writeback membership switchesTejun Heo1-2/+38
sync_inodes_sb() can race against cgwb (cgroup writeback) membership switches and fail to writeback some inodes. For example, if an inode switches to another wb while sync_inodes_sb() is in progress, the new wb might not be visible to bdi_split_work_to_wbs() at all or the inode might jump from a wb which hasn't issued writebacks yet to one which already has. This patch adds backing_dev_info->wb_switch_rwsem to synchronize cgwb switch path against sync_inodes_sb() so that sync_inodes_sb() is guaranteed to see all the target wbs and inodes can't jump wbs to escape syncing. v2: Fixed misplaced rwsem init. Spotted by Jiufei. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Jiufei Xue <xuejiufei@gmail.com> Link: http://lkml.kernel.org/r/dc694ae2-f07f-61e1-7097-7c8411cee12d@gmail.com Acked-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-10-21fs: Convert writeback to XArrayMatthew Wilcox1-16/+9
A couple of short loops. Signed-off-by: Matthew Wilcox <willy@infradead.org>
2018-05-04bdi: Fix oops in wb_workfn()Jan Kara1-1/+1
Syzbot has reported that it can hit a NULL pointer dereference in wb_workfn() due to wb->bdi->dev being NULL. This indicates that wb_workfn() was called for an already unregistered bdi which should not happen as wb_shutdown() called from bdi_unregister() should make sure all pending writeback works are completed before bdi is unregistered. Except that wb_workfn() itself can requeue the work with: mod_delayed_work(bdi_wq, &wb->dwork, 0); and if this happens while wb_shutdown() is waiting in: flush_delayed_work(&wb->dwork); the dwork can get executed after wb_shutdown() has finished and bdi_unregister() has cleared wb->bdi->dev. Make wb_workfn() use wakeup_wb() for requeueing the work which takes all the necessary precautions against racing with bdi unregistration. CC: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> CC: Tejun Heo <tj@kernel.org> Fixes: 839a8e8660b6777e7fe4e80af1a048aebe2b5977 Reported-by: syzbot <syzbot+9873874c735f2892e7e9@syzkaller.appspotmail.com> Reviewed-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-04-21writeback: safer lock nestingGreg Thelen1-3/+4
lock_page_memcg()/unlock_page_memcg() use spin_lock_irqsave/restore() if the page's memcg is undergoing move accounting, which occurs when a process leaves its memcg for a new one that has memory.move_charge_at_immigrate set. unlocked_inode_to_wb_begin,end() use spin_lock_irq/spin_unlock_irq() if the given inode is switching writeback domains. Switches occur when enough writes are issued from a new domain. This existing pattern is thus suspicious: lock_page_memcg(page); unlocked_inode_to_wb_begin(inode, &locked); ... unlocked_inode_to_wb_end(inode, locked); unlock_page_memcg(page); If both inode switch and process memcg migration are both in-flight then unlocked_inode_to_wb_end() will unconditionally enable interrupts while still holding the lock_page_memcg() irq spinlock. This suggests the possibility of deadlock if an interrupt occurs before unlock_page_memcg(). truncate __cancel_dirty_page lock_page_memcg unlocked_inode_to_wb_begin unlocked_inode_to_wb_end <interrupts mistakenly enabled> <interrupt> end_page_writeback test_clear_page_writeback lock_page_memcg <deadlock> unlock_page_memcg Due to configuration limitations this deadlock is not currently possible because we don't mix cgroup writeback (a cgroupv2 feature) and memory.move_charge_at_immigrate (a cgroupv1 feature). If the kernel is hacked to always claim inode switching and memcg moving_account, then this script triggers lockup in less than a minute: cd /mnt/cgroup/memory mkdir a b echo 1 > a/memory.move_charge_at_immigrate echo 1 > b/memory.move_charge_at_immigrate ( echo $BASHPID > a/cgroup.procs while true; do dd if=/dev/zero of=/mnt/big bs=1M count=256 done ) & while true; do sync done & sleep 1h & SLEEP=$! while true; do echo $SLEEP > a/cgroup.procs echo $SLEEP > b/cgroup.procs done The deadlock does not seem possible, so it's debatable if there's any reason to modify the kernel. I suggest we should to prevent future surprises. And Wang Long said "this deadlock occurs three times in our environment", so there's more reason to apply this, even to stable. Stable 4.4 has minor conflicts applying this patch. For a clean 4.4 patch see "[PATCH for-4.4] writeback: safer lock nesting" https://lkml.org/lkml/2018/4/11/146 Wang Long said "this deadlock occurs three times in our environment" [gthelen@google.com: v4] Link: http://lkml.kernel.org/r/20180411084653.254724-1-gthelen@google.com [akpm@linux-foundation.org: comment tweaks, struct initialization simplification] Change-Id: Ibb773e8045852978f6207074491d262f1b3fb613 Link: http://lkml.kernel.org/r/20180410005908.167976-1-gthelen@google.com Fixes: 682aa8e1a6a1 ("writeback: implement unlocked_inode_to_wb transaction and use it for stat updates") Signed-off-by: Greg Thelen <gthelen@google.com> Reported-by: Wang Long <wanglong19@meituan.com> Acked-by: Wang Long <wanglong19@meituan.com> Acked-by: Michal Hocko <mhocko@suse.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Tejun Heo <tj@kernel.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: <stable@vger.kernel.org> [v4.2+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-04-11page cache: use xa_lockMatthew Wilcox1-11/+11
Remove the address_space ->tree_lock and use the xa_lock newly added to the radix_tree_root. Rename the address_space ->page_tree to ->i_pages, since we don't really care that it's a tree. [willy@infradead.org: fix nds32, fs/dax.c] Link: http://lkml.kernel.org/r/20180406145415.GB20605@bombadil.infradead.orgLink: http://lkml.kernel.org/r/20180313132639.17387-9-willy@infradead.org Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com> Acked-by: Jeff Layton <jlayton@redhat.com> Cc: Darrick J. Wong <darrick.wong@oracle.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-03-28fs: move I_DIRTY_INODE to fs.hChristoph Hellwig1-6/+3
And use it in a few more places rather than opencoding the values. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-01-06writeback: update comment in inode_io_list_move_lockedWang Long1-1/+1
The @head can be wb->b_dirty_time, so update the comment. Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Wang Long <wanglong19@meituan.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-11-28Rename superblock flags (MS_xyz -> SB_xyz)Linus Torvalds1-1/+1
This is a pure automated search-and-replace of the internal kernel superblock flags. The s_flags are now called SB_*, with the names and the values for the moment mirroring the MS_* flags that they're equivalent to. Note how the MS_xyz flags are the ones passed to the mount system call, while the SB_xyz flags are what we then use in sb->s_flags. The script to do this was: # places to look in; re security/*: it generally should *not* be # touched (that stuff parses mount(2) arguments directly), but # there are two places where we really deal with superblock flags. FILES="drivers/mtd drivers/staging/lustre fs ipc mm \ include/linux/fs.h include/uapi/linux/bfs_fs.h \ security/apparmor/apparmorfs.c security/apparmor/include/lib.h" # the list of MS_... constants SYMS="RDONLY NOSUID NODEV NOEXEC SYNCHRONOUS REMOUNT MANDLOCK \ DIRSYNC NOATIME NODIRATIME BIND MOVE REC VERBOSE SILENT \ POSIXACL UNBINDABLE PRIVATE SLAVE SHARED RELATIME KERNMOUNT \ I_VERSION STRICTATIME LAZYTIME SUBMOUNT NOREMOTELOCK NOSEC BORN \ ACTIVE NOUSER" SED_PROG= for i in $SYMS; do SED_PROG="$SED_PROG -e s/MS_$i/SB_$i/g"; done # we want files that contain at least one of MS_..., # with fs/namespace.c and fs/pnode.c excluded. L=$(for i in $SYMS; do git grep -w -l MS_$i $FILES; done| sort|uniq|grep -v '^fs/namespace.c'|grep -v '^fs/pnode.c') for f in $L; do sed -i $f $SED_PROG; done Requested-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-10-10writeback: merge try_to_writeback_inodes_sb_nr() into callerRakesh Pandit1-24/+6
Since commit 925a6efb8ff0c ("Btrfs: stop using try_to_writeback_inodes_sb_nr to flush delalloc") this function hasn't been used outside so stop exporting it. In addition we merge it into try_to_writeback_inodes_sb() which is the only caller. Also change return type of try_to_writeback_inodes_sb to void as the only user ext4 doesn't care. Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Rakesh Pandit <rakesh@tuxera.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-10-04writeback: eliminate work item allocation in bd_start_writeback()Jens Axboe1-37/+34
Handle start-all writeback like we do periodic or kupdate style writeback - by marking the bdi_writeback as needing a full flush, and simply waking the thread. This eliminates the need to allocate and queue a specific work item just for this purpose. After this change, we truly only ever have one of them running at any point in time. We mark the need to start all flushes, and the writeback thread will clear it once it has processed the request. Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-10-03writeback: only allow one inflight and pending full flushJens Axboe1-0/+25
When someone calls wakeup_flusher_threads() or wakeup_flusher_threads_bdi(), they schedule writeback of all dirty pages in the system (or on that bdi). If we are tight on memory, we can get tons of these queued from kswapd/vmscan. This causes (at least) two problems: 1) We consume a ton of memory just allocating writeback work items. We've seen as much as 600 million of these writeback work items pending. That's a lot of memory to pointlessly hold hostage, while the box is under memory pressure. 2) We spend so much time processing these work items, that we introduce a softlockup in writeback processing. This is because each of the writeback work items don't end up doing any work (it's hard when you have millions of identical ones coming in to the flush machinery), so we just sit in a tight loop pulling work items and deleting/freeing them. Fix this by adding a 'start_all' bit to the writeback structure, and set that when someone attempts to flush all dirty pages. The bit is cleared when we start writeback on that work item. If the bit is already set when we attempt to queue !nr_pages writeback, then we simply ignore it. This provides us one full flush in flight, with one pending as well, and makes for more efficient handling of this type of writeback. Acked-by: Johannes Weiner <hannes@cmpxchg.org> Tested-by: Chris Mason <clm@fb.com> Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-10-03writeback: move nr_pages == 0 logic to one locationJens Axboe1-24/+17
Now that we have no external callers of wb_start_writeback(), we can shuffle the passing in of 'nr_pages'. Everybody passes in 0 at this point, so just kill the argument and move the dirty count retrieval to that function. Acked-by: Johannes Weiner <hannes@cmpxchg.org> Tested-by: Chris Mason <clm@fb.com> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-10-03writeback: make wb_start_writeback() staticJens Axboe1-2/+2
We don't have any callers outside of fs-writeback.c anymore, make it private. Acked-by: Johannes Weiner <hannes@cmpxchg.org> Tested-by: Chris Mason <clm@fb.com> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-10-03writeback: provide a wakeup_flusher_threads_bdi()Jens Axboe1-10/+29
Similar to wakeup_flusher_threads(), except that we only wake up the flusher threads on the specified backing device. No functional changes in this patch. Acked-by: Johannes Weiner <hannes@cmpxchg.org> Tested-by: Chris Mason <clm@fb.com> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-10-03writeback: remove 'range_cyclic' argument for wb_start_writeback()Jens Axboe1-3/+3
All the callers pass in 'true' for range_cyclic, so kill the argument. Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-10-03writeback: switch wakeup_flusher_threads() to cyclic writebackJens Axboe1-1/+1
We're writing back the full range of dirty pages on the devices, there's no point in making this special and not do normal range cyclic writeback. Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-10-03fs: kill 'nr_pages' argument from wakeup_flusher_threads()Jens Axboe1-5/+4
Everybody is passing in 0 now, let's get rid of the argument. Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2017-07-13writeback: rework wb_[dec|inc]_stat family of functionsNikolay Borisov1-4/+4
Currently the writeback statistics code uses a percpu counters to hold various statistics. Furthermore we have 2 families of functions - those which disable local irq and those which doesn't and whose names begin with double underscore. However, they both end up calling __add_wb_stats which in turn calls percpu_counter_add_batch which is already irq-safe. Exploiting this fact allows to eliminated the __wb_* functions since they don't add any further protection than we already have. Furthermore, refactor the wb_* function to call __add_wb_stat directly without the irq-disabling dance. This will likely result in better runtime of code which deals with modifying the stat counters. While at it also document why percpu_counter_add_batch is in fact preempt and irq-safe since at least 3 people got confused. Link: http://lkml.kernel.org/r/1498029937-27293-1-git-send-email-nborisov@suse.com Signed-off-by: Nikolay Borisov <nborisov@suse.com> Acked-by: Tejun Heo <tj@kernel.org> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Josef Bacik <jbacik@fb.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Jeff Layton <jlayton@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-05-16fs: add a blank lines on some kernel-doc commentsMauro Carvalho Chehab1-5/+7
Sphinx gets confused when it finds identation without a good reason for it and without a preceding blank line: ./fs/mpage.c:347: ERROR: Unexpected indentation. ./fs/namei.c:4303: ERROR: Unexpected indentation. ./fs/fs-writeback.c:2060: ERROR: Unexpected indentation. No functional changes. Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
2017-03-13writeback: fix memory leak in wb_queue_work()Tahsin Erdogan1-14/+21
When WB_registered flag is not set, wb_queue_work() skips queuing the work, but does not perform the necessary clean up. In particular, if work->auto_free is true, it should free the memory. The leak condition can be reprouced by following these steps: mount /dev/sdb /mnt/sdb /* In qemu console: device_del sdb */ umount /dev/sdb Above will result in a wb_queue_work() call on an unregistered wb and thus leak memory. Reported-by: John Sperbeck <jsperbeck@google.com> Signed-off-by: Tahsin Erdogan <tahsin@google.com> Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-12-13fs/fs-writeback.c: remove redundant if checkTahsin Erdogan1-9/+7
b_more_io non-empty check is already preceded by an opposite check. Link: http://lkml.kernel.org/r/1478591249-30641-1-git-send-email-tahsin@google.com Signed-off-by: Tahsin Erdogan <tahsin@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-08-10mm, writeback: flush plugged IO in wakeup_flusher_threads()Konstantin Khlebnikov1-0/+6
I've found funny live-lock between raid10 barriers during resync and memory controller hard limits. Inside mpage_readpages() task holds on to its plug bio which blocks the barrier in raid10. Its memory cgroup have no free memory thus the task goes into reclaimer but all reclaimable pages are dirty and cannot be written because raid10 is rebuilding and stuck on the barrier. Common flush of such IO in schedule() never happens, because the caller doesn't go to sleep. Lock is 'live' because changing memory limit or killing tasks which holds that stuck bio unblock whole progress. That was what happened in 3.18.x but I see no difference in upstream logic. Theoretically this might happen even without memory cgroup. Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-08-04writeback: Write dirty times for WB_SYNC_ALL writebackJan Kara1-0/+1
Currently we take care to handle I_DIRTY_TIME in vfs_fsync() and queue_io() so that inodes which have only dirty timestamps are properly written on fsync(2) and sync(2). However there are other call sites - most notably going through write_inode_now() - which expect inode to be clean after WB_SYNC_ALL writeback. This is not currently true as we do not clear I_DIRTY_TIME in __writeback_single_inode() even for WB_SYNC_ALL writeback in all the cases. This then resulted in the following oops because bdev_write_inode() did not clean the inode and writeback code later stumbled over a dirty inode with detached wb. general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN Modules linked in: CPU: 3 PID: 32 Comm: kworker/u10:1 Not tainted 4.6.0-rc3+ #349 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Workqueue: writeback wb_workfn (flush-11:0) task: ffff88006ccf1840 ti: ffff88006cda8000 task.ti: ffff88006cda8000 RIP: 0010:[<ffffffff818884d2>] [<ffffffff818884d2>] locked_inode_to_wb_and_lock_list+0xa2/0x750 RSP: 0018:ffff88006cdaf7d0 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88006ccf2050 RDX: 0000000000000000 RSI: 000000114c8a8484 RDI: 0000000000000286 RBP: ffff88006cdaf820 R08: ffff88006ccf1840 R09: 0000000000000000 R10: 000229915090805f R11: 0000000000000001 R12: ffff88006a72f5e0 R13: dffffc0000000000 R14: ffffed000d4e5eed R15: ffffffff8830cf40 FS: 0000000000000000(0000) GS:ffff88006d500000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000003301bf8 CR3: 000000006368f000 CR4: 00000000000006e0 DR0: 0000000000001ec9 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 Stack: ffff88006a72f680 ffff88006a72f768 ffff8800671230d8 03ff88006cdaf948 ffff88006a72f668 ffff88006a72f5e0 ffff8800671230d8 ffff88006cdaf948 ffff880065b90cc8 ffff880067123100 ffff88006cdaf970 ffffffff8188e12e Call Trace: [< inline >] inode_to_wb_and_lock_list fs/fs-writeback.c:309 [<ffffffff8188e12e>] writeback_sb_inodes+0x4de/0x1250 fs/fs-writeback.c:1554 [<ffffffff8188efa4>] __writeback_inodes_wb+0x104/0x1e0 fs/fs-writeback.c:1600 [<ffffffff8188f9ae>] wb_writeback+0x7ce/0xc90 fs/fs-writeback.c:1709 [< inline >] wb_do_writeback fs/fs-writeback.c:1844 [<ffffffff81891079>] wb_workfn+0x2f9/0x1000 fs/fs-writeback.c:1884 [<ffffffff813bcd1e>] process_one_work+0x78e/0x15c0 kernel/workqueue.c:2094 [<ffffffff813bdc2b>] worker_thread+0xdb/0xfc0 kernel/workqueue.c:2228 [<ffffffff813cdeef>] kthread+0x23f/0x2d0 drivers/block/aoe/aoecmd.c:1303 [<ffffffff867bc5d2>] ret_from_fork+0x22/0x50 arch/x86/entry/entry_64.S:392 Code: 05 94 4a a8 06 85 c0 0f 85 03 03 00 00 e8 07 15 d0 ff 41 80 3e 00 0f 85 64 06 00 00 49 8b 9c 24 88 01 00 00 48 89 d8 48 c1 e8 03 <42> 80 3c 28 00 0f 85 17 06 00 00 48 8b 03 48 83 c0 50 48 39 c3 RIP [< inline >] wb_get include/linux/backing-dev-defs.h:212 RIP [<ffffffff818884d2>] locked_inode_to_wb_and_lock_list+0xa2/0x750 fs/fs-writeback.c:281 RSP <ffff88006cdaf7d0> ---[ end trace 986a4d314dcb2694 ]--- Fix the problem by making sure __writeback_single_inode() writes inode only with dirty times in WB_SYNC_ALL mode. Reported-by: Dmitry Vyukov <dvyukov@google.com> Tested-by: Laurent Dufour <ldufour@linux.vnet.ibm.com> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-07-29mm: move most file-based accounting to the nodeMel Gorman1-2/+2
There are now a number of accounting oddities such as mapped file pages being accounted for on the node while the total number of file pages are accounted on the zone. This can be coped with to some extent but it's confusing so this patch moves the relevant file-based accounted. Due to throttling logic in the page allocator for reliable OOM detection, it is still necessary to track dirty and writeback pages on a per-zone basis. [mgorman@techsingularity.net: fix NR_ZONE_WRITE_PENDING accounting] Link: http://lkml.kernel.org/r/1468404004-5085-5-git-send-email-mgorman@techsingularity.net Link: http://lkml.kernel.org/r/1467970510-21195-20-git-send-email-mgorman@techsingularity.net Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Minchan Kim <minchan@kernel.org> Cc: Rik van Riel <riel@surriel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-07-27fs/fs-writeback.c: inode writeback list tracking tracepointsBrian Foster1-2/+7
The per-sb inode writeback list tracks inodes currently under writeback to facilitate efficient sync processing. In particular, it ensures that sync only needs to walk through a list of inodes that were cleaned by the sync. Add a couple tracepoints to help identify when inodes are added/removed to and from the writeback lists. Piggyback off of the writeback lazytime tracepoint template as it already tracks the relevant inode information. Link: http://lkml.kernel.org/r/1466594593-6757-3-git-send-email-bfoster@redhat.com Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Dave Chinner <dchinner@redhat.com> cc: Josef Bacik <jbacik@fb.com> Cc: Holger Hoffstätte <holger.hoffstaette@applied-asynchrony.com> Cc: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-07-27fs/fs-writeback.c: add a new writeback list for syncDave Chinner1-25/+81
wait_sb_inodes() currently does a walk of all inodes in the filesystem to find dirty one to wait on during sync. This is highly inefficient and wastes a lot of CPU when there are lots of clean cached inodes that we don't need to wait on. To avoid this "all inode" walk, we need to track inodes that are currently under writeback that we need to wait for. We do this by adding inodes to a writeback list on the sb when the mapping is first tagged as having pages under writeback. wait_sb_inodes() can then walk this list of "inodes under IO" and wait specifically just for the inodes that the current sync(2) needs to wait for. Define a couple helpers to add/remove an inode from the writeback list and call them when the overall mapping is tagged for or cleared from writeback. Update wait_sb_inodes() to walk only the inodes under writeback due to the sync. With this change, filesystem sync times are significantly reduced for fs' with largely populated inode caches and otherwise no other work to do. For example, on a 16xcpu 2GHz x86-64 server, 10TB XFS filesystem with a ~10m entry inode cache, sync times are reduced from ~7.3s to less than 0.1s when the filesystem is fully clean. Link: http://lkml.kernel.org/r/1466594593-6757-2-git-send-email-bfoster@redhat.com Signed-off-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Josef Bacik <jbacik@fb.com> Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Jan Kara <jack@suse.cz> Tested-by: Holger Hoffstätte <holger.hoffstaette@applied-asynchrony.com> Cc: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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