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* writeback: fix a subtle race condition in I_DIRTY clearingTejun Heo2014-11-041-7/+22
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | After invoking ->dirty_inode(), __mark_inode_dirty() does smp_mb() and tests inode->i_state locklessly to see whether it already has all the necessary I_DIRTY bits set. The comment above the barrier doesn't contain any useful information - memory barriers can't ensure "changes are seen by all cpus" by itself. And it sure enough was broken. Please consider the following scenario. CPU 0 CPU 1 ------------------------------------------------------------------------------- enters __writeback_single_inode() grabs inode->i_lock tests PAGECACHE_TAG_DIRTY which is clear enters __set_page_dirty() grabs mapping->tree_lock sets PAGECACHE_TAG_DIRTY releases mapping->tree_lock leaves __set_page_dirty() enters __mark_inode_dirty() smp_mb() sees I_DIRTY_PAGES set leaves __mark_inode_dirty() clears I_DIRTY_PAGES releases inode->i_lock Now @inode has dirty pages w/ I_DIRTY_PAGES clear. This doesn't seem to lead to an immediately critical problem because requeue_inode() later checks PAGECACHE_TAG_DIRTY instead of I_DIRTY_PAGES when deciding whether the inode needs to be requeued for IO and there are enough unintentional memory barriers inbetween, so while the inode ends up with inconsistent I_DIRTY_PAGES flag, it doesn't fall off the IO list. The lack of explicit barrier may also theoretically affect the other I_DIRTY bits which deal with metadata dirtiness. There is no guarantee that a strong enough barrier exists between I_DIRTY_[DATA]SYNC clearing and write_inode() writing out the dirtied inode. Filesystem inode writeout path likely has enough stuff which can behave as full barrier but it's theoretically possible that the writeout may not see all the updates from ->dirty_inode(). Fix it by adding an explicit smp_mb() after I_DIRTY clearing. Note that I_DIRTY_PAGES needs a special treatment as it always needs to be cleared to be interlocked with the lockless test on __mark_inode_dirty() side. It's cleared unconditionally and reinstated after smp_mb() if the mapping still has dirty pages. Also add comments explaining how and why the barriers are paired. Lightly tested. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Jan Kara <jack@suse.cz> Cc: Mikulas Patocka <mpatocka@redhat.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: stable@vger.kernel.org Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@fb.com>
* sched: Remove proliferation of wait_on_bit() action functionsNeilBrown2014-07-161-1/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The current "wait_on_bit" interface requires an 'action' function to be provided which does the actual waiting. There are over 20 such functions, many of them identical. Most cases can be satisfied by one of just two functions, one which uses io_schedule() and one which just uses schedule(). So: Rename wait_on_bit and wait_on_bit_lock to wait_on_bit_action and wait_on_bit_lock_action to make it explicit that they need an action function. Introduce new wait_on_bit{,_lock} and wait_on_bit{,_lock}_io which are *not* given an action function but implicitly use a standard one. The decision to error-out if a signal is pending is now made based on the 'mode' argument rather than being encoded in the action function. All instances of the old wait_on_bit and wait_on_bit_lock which can use the new version have been changed accordingly and their action functions have been discarded. wait_on_bit{_lock} does not return any specific error code in the event of a signal so the caller must check for non-zero and interpolate their own error code as appropriate. The wait_on_bit() call in __fscache_wait_on_invalidate() was ambiguous as it specified TASK_UNINTERRUPTIBLE but used fscache_wait_bit_interruptible as an action function. David Howells confirms this should be uniformly "uninterruptible" The main remaining user of wait_on_bit{,_lock}_action is NFS which needs to use a freezer-aware schedule() call. A comment in fs/gfs2/glock.c notes that having multiple 'action' functions is useful as they display differently in the 'wchan' field of 'ps'. (and /proc/$PID/wchan). As the new bit_wait{,_io} functions are tagged "__sched", they will not show up at all, but something higher in the stack. So the distinction will still be visible, only with different function names (gds2_glock_wait versus gfs2_glock_dq_wait in the gfs2/glock.c case). Since first version of this patch (against 3.15) two new action functions appeared, on in NFS and one in CIFS. CIFS also now uses an action function that makes the same freezer aware schedule call as NFS. Signed-off-by: NeilBrown <neilb@suse.de> Acked-by: David Howells <dhowells@redhat.com> (fscache, keys) Acked-by: Steven Whitehouse <swhiteho@redhat.com> (gfs2) Acked-by: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Steve French <sfrench@samba.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/20140707051603.28027.72349.stgit@notabene.brown Signed-off-by: Ingo Molnar <mingo@kernel.org>
* Merge tag 'gfs2-merge-window' of ↵Linus Torvalds2014-04-041-0/+2
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/steve/gfs2-3.0-nmw Pull GFS2 updates from Steven Whitehouse: "One of the main highlights this time, is not the patches themselves but instead the widening contributor base. It is good to see that interest is increasing in GFS2, and I'd like to thank all the contributors to this patch set. In addition to the usual set of bug fixes and clean ups, there are patches to improve inode creation performance when xattrs are required and some improvements to the transaction code which is intended to help improve scalability after further changes in due course. Journal extent mapping is also updated to make it more efficient and again, this is a foundation for future work in this area. The maximum number of ACLs has been increased to 300 (for a 4k block size) which means that even with a few additional xattrs from selinux, everything should fit within a single fs block. There is also a patch to bring GFS2's own copy of the writepages code up to the same level as the core VFS. Eventually we may be able to merge some of this code, since it is fairly similar. The other major change this time, is bringing consistency to the printing of messages via fs_<level>, pr_<level> macros" * tag 'gfs2-merge-window' of git://git.kernel.org/pub/scm/linux/kernel/git/steve/gfs2-3.0-nmw: (29 commits) GFS2: Fix address space from page function GFS2: Fix uninitialized VFS inode in gfs2_create_inode GFS2: Fix return value in slot_get() GFS2: inline function gfs2_set_mode GFS2: Remove extraneous function gfs2_security_init GFS2: Increase the max number of ACLs GFS2: Re-add a call to log_flush_wait when flushing the journal GFS2: Ensure workqueue is scheduled after noexp request GFS2: check NULL return value in gfs2_ok_to_move GFS2: Convert gfs2_lm_withdraw to use fs_err GFS2: Use fs_<level> more often GFS2: Use pr_<level> more consistently GFS2: Move recovery variables to journal structure in memory GFS2: global conversion to pr_foo() GFS2: return -E2BIG if hit the maximum limits of ACLs GFS2: Clean up journal extent mapping GFS2: replace kmalloc - __vmalloc / memset 0 GFS2: Remove extra "if" in gfs2_log_flush() fs: NULL dereference in posix_acl_to_xattr() GFS2: Move log buffer accounting to transaction ...
| * GFS2: journal data writepages updateSteven Whitehouse2014-02-061-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | GFS2 has carried what is more or less a copy of the write_cache_pages() for some time. It seems that this copy has slipped behind the core code over time. This patch brings it back uptodate, and in addition adds the tracepoint which would otherwise be missing. We could go further, and eliminate some or all of the code duplication here. The issue is that if we do that, then the function we need to split out from the existing write_cache_pages(), which will look a lot like gfs2_jdata_write_pagevec(), would land up putting quite a lot of extra variables on the stack. I know that has been a problem in the past in the writeback code path, which is why I've hesitated to do it here. Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
* | bdi: avoid oops on device removalJan Kara2014-04-031-5/+18
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | After commit 839a8e8660b6 ("writeback: replace custom worker pool implementation with unbound workqueue") when device is removed while we are writing to it we crash in bdi_writeback_workfn() -> set_worker_desc() because bdi->dev is NULL. This can happen because even though bdi_unregister() cancels all pending flushing work, nothing really prevents new ones from being queued from balance_dirty_pages() or other places. Fix the problem by clearing BDI_registered bit in bdi_unregister() and checking it before scheduling of any flushing work. Fixes: 839a8e8660b6777e7fe4e80af1a048aebe2b5977 Reviewed-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jan Kara <jack@suse.cz> Cc: Derek Basehore <dbasehore@chromium.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>
* | backing_dev: fix hung task on syncDerek Basehore2014-04-031-4/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | bdi_wakeup_thread_delayed() used the mod_delayed_work() function to schedule work to writeback dirty inodes. The problem with this is that it can delay work that is scheduled for immediate execution, such as the work from sync_inodes_sb(). This can happen since mod_delayed_work() can now steal work from a work_queue. This fixes the problem by using queue_delayed_work() instead. This is a regression caused by commit 839a8e8660b6 ("writeback: replace custom worker pool implementation with unbound workqueue"). The reason that this causes a problem is that laptop-mode will change the delay, dirty_writeback_centisecs, to 60000 (10 minutes) by default. In the case that bdi_wakeup_thread_delayed() races with sync_inodes_sb(), sync will be stopped for 10 minutes and trigger a hung task. Even if dirty_writeback_centisecs is not long enough to cause a hung task, we still don't want to delay sync for that long. We fix the problem by using queue_delayed_work() when we want to schedule writeback sometime in future. This function doesn't change the timer if it is already armed. For the same reason, we also change bdi_writeback_workfn() to immediately queue the work again in the case that the work_list is not empty. The same problem can happen if the sync work is run on the rescue worker. [jack@suse.cz: update changelog, add comment, use bdi_wakeup_thread_delayed()] Signed-off-by: Derek Basehore <dbasehore@chromium.org> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Alexander Viro <viro@zento.linux.org.uk> Reviewed-by: Tejun Heo <tj@kernel.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: "Darrick J. Wong" <darrick.wong@oracle.com> Cc: Derek Basehore <dbasehore@chromium.org> Cc: Kees Cook <keescook@chromium.org> Cc: Benson Leung <bleung@chromium.org> Cc: Sonny Rao <sonnyrao@chromium.org> Cc: Luigi Semenzato <semenzato@chromium.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Dave Chinner <david@fromorbit.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | Revert "writeback: do not sync data dirtied after sync start"Jan Kara2014-02-221-22/+11
|/ | | | | | | | | | | | | | This reverts commit c4a391b53a72d2df4ee97f96f78c1d5971b47489. Dave Chinner <david@fromorbit.com> has reported the commit may cause some inodes to be left out from sync(2). This is because we can call redirty_tail() for some inode (which sets i_dirtied_when to current time) after sync(2) has started or similarly requeue_inode() can set i_dirtied_when to current time if writeback had to skip some pages. The real problem is in the functions clobbering i_dirtied_when but fixing that isn't trivial so revert is a safer choice for now. CC: stable@vger.kernel.org # >= 3.13 Signed-off-by: Jan Kara <jack@suse.cz>
* writeback: Fix data corruption on NFSJan Kara2013-12-141-6/+9
| | | | | | | | | | | | | | | | | | | Commit 4f8ad655dbc8 "writeback: Refactor writeback_single_inode()" added a condition to skip clean inode. However this is wrong in WB_SYNC_ALL mode because there we also want to wait for outstanding writeback on possibly clean inode. This was causing occasional data corruption issues on NFS because it uses sync_inode() to make sure all outstanding writes are flushed to the server before truncating the inode and with sync_inode() returning prematurely file was sometimes extended back by an outstanding write after it was truncated. So modify the test to also check for pages under writeback in WB_SYNC_ALL mode. CC: stable@vger.kernel.org # >= 3.5 Fixes: 4f8ad655dbc82cf05d2edc11e66b78a42d38bf93 Reported-and-tested-by: Dan Duval <dan.duval@oracle.com> Signed-off-by: Jan Kara <jack@suse.cz>
* Merge branch 'akpm' (patches from Andrew Morton)Linus Torvalds2013-11-131-11/+22
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Merge first patch-bomb from Andrew Morton: "Quite a lot of other stuff is banked up awaiting further next->mainline merging, but this batch contains: - Lots of random misc patches - OCFS2 - Most of MM - backlight updates - lib/ updates - printk updates - checkpatch updates - epoll tweaking - rtc updates - hfs - hfsplus - documentation - procfs - update gcov to gcc-4.7 format - IPC" * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (269 commits) ipc, msg: fix message length check for negative values ipc/util.c: remove unnecessary work pending test devpts: plug the memory leak in kill_sb ./Makefile: export initial ramdisk compression config option init/Kconfig: add option to disable kernel compression drivers: w1: make w1_slave::flags long to avoid memory corruption drivers/w1/masters/ds1wm.cuse dev_get_platdata() drivers/memstick/core/ms_block.c: fix unreachable state in h_msb_read_page() drivers/memstick/core/mspro_block.c: fix attributes array allocation drivers/pps/clients/pps-gpio.c: remove redundant of_match_ptr kernel/panic.c: reduce 1 byte usage for print tainted buffer gcov: reuse kbasename helper kernel/gcov/fs.c: use pr_warn() kernel/module.c: use pr_foo() gcov: compile specific gcov implementation based on gcc version gcov: add support for gcc 4.7 gcov format gcov: move gcov structs definitions to a gcc version specific file kernel/taskstats.c: return -ENOMEM when alloc memory fails in add_del_listener() kernel/taskstats.c: add nla_nest_cancel() for failure processing between nla_nest_start() and nla_nest_end() kernel/sysctl_binary.c: use scnprintf() instead of snprintf() ...
| * writeback: do not sync data dirtied after sync startJan Kara2013-11-131-11/+22
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When there are processes heavily creating small files while sync(2) is running, it can easily happen that quite some new files are created between WB_SYNC_NONE and WB_SYNC_ALL pass of sync(2). That can happen especially if there are several busy filesystems (remember that sync traverses filesystems sequentially and waits in WB_SYNC_ALL phase on one fs before starting it on another fs). Because WB_SYNC_ALL pass is slow (e.g. causes a transaction commit and cache flush for each inode in ext3), resulting sync(2) times are rather large. The following script reproduces the problem: function run_writers { for (( i = 0; i < 10; i++ )); do mkdir $1/dir$i for (( j = 0; j < 40000; j++ )); do dd if=/dev/zero of=$1/dir$i/$j bs=4k count=4 &>/dev/null done & done } for dir in "$@"; do run_writers $dir done sleep 40 time sync Fix the problem by disregarding inodes dirtied after sync(2) was called in the WB_SYNC_ALL pass. To allow for this, sync_inodes_sb() now takes a time stamp when sync has started which is used for setting up work for flusher threads. To give some numbers, when above script is run on two ext4 filesystems on simple SATA drive, the average sync time from 10 runs is 267.549 seconds with standard deviation 104.799426. With the patched kernel, the average sync time from 10 runs is 2.995 seconds with standard deviation 0.096. Signed-off-by: Jan Kara <jack@suse.cz> Reviewed-by: Fengguang Wu <fengguang.wu@intel.com> Reviewed-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | new helpers: lock_mount_hash/unlock_mount_hashAl Viro2013-10-241-0/+1
|/ | | | | | | aka br_write_{lock,unlock} of vfsmount_lock. Inlines in fs/mount.h, vfsmount_lock extern moved over there as well. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* Merge tag 'writeback-fixes' of ↵Linus Torvalds2013-09-131-3/+5
|\ | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux Pull writeback fix from Wu Fengguang: "A trivial writeback fix" * tag 'writeback-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux: writeback: Do not sort b_io list only because of block device inode
| * writeback: Do not sort b_io list only because of block device inodeJan Kara2013-07-091-3/+5
| | | | | | | | | | | | | | | | | | | | It is very likely that block device inode will be part of BDI dirty list as well. However it doesn't make sence to sort inodes on the b_io list just because of this inode (as it contains buffers all over the device anyway). So save some CPU cycles which is valuable since we hold relatively contented wb->list_lock. Signed-off-by: Jan Kara <jack@suse.cz>
* | writeback: fix race that cause writeback hungJunxiao Bi2013-09-111-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There is a race between mark inode dirty and writeback thread, see the following scenario. In this case, writeback thread will not run though there is dirty_io. __mark_inode_dirty() bdi_writeback_workfn() ... ... spin_lock(&inode->i_lock); ... if (bdi_cap_writeback_dirty(bdi)) { <<< assume wb has dirty_io, so wakeup_bdi is false. <<< the following inode_dirty also have wakeup_bdi false. if (!wb_has_dirty_io(&bdi->wb)) wakeup_bdi = true; } spin_unlock(&inode->i_lock); <<< assume last dirty_io is removed here. pages_written = wb_do_writeback(wb); ... <<< work_list empty and wb has no dirty_io, <<< delayed_work will not be queued. if (!list_empty(&bdi->work_list) || (wb_has_dirty_io(wb) && dirty_writeback_interval)) queue_delayed_work(bdi_wq, &wb->dwork, msecs_to_jiffies(dirty_writeback_interval * 10)); spin_lock(&bdi->wb.list_lock); inode->dirtied_when = jiffies; <<< new dirty_io is added. list_move(&inode->i_wb_list, &bdi->wb.b_dirty); spin_unlock(&bdi->wb.list_lock); <<< though there is dirty_io, but wakeup_bdi is false, <<< so writeback thread will not be waked up and <<< the new dirty_io will not be flushed. if (wakeup_bdi) bdi_wakeup_thread_delayed(bdi); Writeback will run until there is a new flush work queued. This may cause a lot of dirty pages stay in memory for a long time. Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | mm/writeback: make writeback_inodes_wb staticWanpeng Li2013-09-111-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | It's not used globally and could be static. Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Rik van Riel <riel@redhat.com> Cc: Fengguang Wu <fengguang.wu@intel.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Tejun Heo <tj@kernel.org> Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com> Cc: David Rientjes <rientjes@google.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Jiri Kosina <jkosina@suse.cz> Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | writeback: fix occasional slow sync(1)Jan Kara2013-09-111-4/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In case when system contains no dirty pages, wakeup_flusher_threads() will submit WB_SYNC_NONE writeback for 0 pages so wb_writeback() exits immediately without doing anything, even though there are dirty inodes in the system. Thus sync(1) will write all the dirty inodes from a WB_SYNC_ALL writeback pass which is slow. Fix the problem by using get_nr_dirty_pages() in wakeup_flusher_threads() instead of calculating number of dirty pages manually. That function also takes number of dirty inodes into account. Signed-off-by: Jan Kara <jack@suse.cz> Reported-by: Paul Taysom <taysom@chromium.org> Cc: Wu Fengguang <fengguang.wu@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | mm/writeback: don't check force_wait to handle bdi->work_listWanpeng Li2013-07-091-8/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | After commit 839a8e8660b6 ("writeback: replace custom worker pool implementation with unbound workqueue"), bdi_writeback_workfn runs off bdi_writeback->dwork, on each execution, it processes bdi->work_list and reschedules if there are more things to do instead of flush any work that race with us existing. It is unecessary to check force_wait in wb_do_writeback since it is always 0 after the mentioned commit. This patch remove the force_wait in wb_do_writeback. Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com> Reviewed-by: Tejun Heo <tj@kernel.org> Reviewed-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | fs/fs-writeback.c: : make wb_do_writeback() as staticHaicheng Li2013-07-091-1/+1
| | | | | | | | | | | | | | | | | | | | | | It's not used globally and could be static. Signed-off-by: Haicheng Li <haicheng.li@linux.intel.com> Cc: Jan Kara <jack@suse.cz> Cc: Wu Fengguang <fengguang.wu@intel.com> Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | sync: don't block the flusher thread waiting on IODave Chinner2013-07-021-2/+7
|/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When sync does it's WB_SYNC_ALL writeback, it issues data Io and then immediately waits for IO completion. This is done in the context of the flusher thread, and hence completely ties up the flusher thread for the backing device until all the dirty inodes have been synced. On filesystems that are dirtying inodes constantly and quickly, this means the flusher thread can be tied up for minutes per sync call and hence badly affect system level write IO performance as the page cache cannot be cleaned quickly. We already have a wait loop for IO completion for sync(2), so cut this out of the flusher thread and delegate it to wait_sb_inodes(). Hence we can do rapid IO submission, and then wait for it all to complete. Effect of sync on fsmark before the patch: FSUse% Count Size Files/sec App Overhead ..... 0 640000 4096 35154.6 1026984 0 720000 4096 36740.3 1023844 0 800000 4096 36184.6 916599 0 880000 4096 1282.7 1054367 0 960000 4096 3951.3 918773 0 1040000 4096 40646.2 996448 0 1120000 4096 43610.1 895647 0 1200000 4096 40333.1 921048 And a single sync pass took: real 0m52.407s user 0m0.000s sys 0m0.090s After the patch, there is no impact on fsmark results, and each individual sync(2) operation run concurrently with the same fsmark workload takes roughly 7s: real 0m6.930s user 0m0.000s sys 0m0.039s IOWs, sync is 7-8x faster on a busy filesystem and does not have an adverse impact on ongoing async data write operations. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Merge branch 'for-3.10/core' of git://git.kernel.dk/linux-blockLinus Torvalds2013-05-081-70/+32
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Pull block core updates from Jens Axboe: - Major bit is Kents prep work for immutable bio vecs. - Stable candidate fix for a scheduling-while-atomic in the queue bypass operation. - Fix for the hang on exceeded rq->datalen 32-bit unsigned when merging discard bios. - Tejuns changes to convert the writeback thread pool to the generic workqueue mechanism. - Runtime PM framework, SCSI patches exists on top of these in James' tree. - A few random fixes. * 'for-3.10/core' of git://git.kernel.dk/linux-block: (40 commits) relay: move remove_buf_file inside relay_close_buf partitions/efi.c: replace useless kzalloc's by kmalloc's fs/block_dev.c: fix iov_shorten() criteria in blkdev_aio_read() block: fix max discard sectors limit blkcg: fix "scheduling while atomic" in blk_queue_bypass_start Documentation: cfq-iosched: update documentation help for cfq tunables writeback: expose the bdi_wq workqueue writeback: replace custom worker pool implementation with unbound workqueue writeback: remove unused bdi_pending_list aoe: Fix unitialized var usage bio-integrity: Add explicit field for owner of bip_buf block: Add an explicit bio flag for bios that own their bvec block: Add bio_alloc_pages() block: Convert some code to bio_for_each_segment_all() block: Add bio_for_each_segment_all() bounce: Refactor __blk_queue_bounce to not use bi_io_vec raid1: use bio_copy_data() pktcdvd: Use bio_reset() in disabled code to kill bi_idx usage pktcdvd: use bio_copy_data() block: Add bio_copy_data() ...
| * writeback: replace custom worker pool implementation with unbound workqueueTejun Heo2013-04-011-70/+32
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Writeback implements its own worker pool - each bdi can be associated with a worker thread which is created and destroyed dynamically. The worker thread for the default bdi is always present and serves as the "forker" thread which forks off worker threads for other bdis. there's no reason for writeback to implement its own worker pool when using unbound workqueue instead is much simpler and more efficient. This patch replaces custom worker pool implementation in writeback with an unbound workqueue. The conversion isn't too complicated but the followings are worth mentioning. * bdi_writeback->last_active, task and wakeup_timer are removed. delayed_work ->dwork is added instead. Explicit timer handling is no longer necessary. Everything works by either queueing / modding / flushing / canceling the delayed_work item. * bdi_writeback_thread() becomes bdi_writeback_workfn() which runs off bdi_writeback->dwork. On each execution, it processes bdi->work_list and reschedules itself if there are more things to do. The function also handles low-mem condition, which used to be handled by the forker thread. If the function is running off a rescuer thread, it only writes out limited number of pages so that the rescuer can serve other bdis too. This preserves the flusher creation failure behavior of the forker thread. * INIT_LIST_HEAD(&bdi->bdi_list) is used to tell bdi_writeback_workfn() about on-going bdi unregistration so that it always drains work_list even if it's running off the rescuer. Note that the original code was broken in this regard. Under memory pressure, a bdi could finish unregistration with non-empty work_list. * The default bdi is no longer special. It now is treated the same as any other bdi and bdi_cap_flush_forker() is removed. * BDI_pending is no longer used. Removed. * Some tracepoints become non-applicable. The following TPs are removed - writeback_nothread, writeback_wake_thread, writeback_wake_forker_thread, writeback_thread_start, writeback_thread_stop. Everything, including devices coming and going away and rescuer operation under simulated memory pressure, seems to work fine in my test setup. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Jens Axboe <axboe@kernel.dk> Cc: Fengguang Wu <fengguang.wu@intel.com> Cc: Jeff Moyer <jmoyer@redhat.com>
* | writeback: set worker desc to identify writeback workers in task dumpsTejun Heo2013-04-301-0/+1
|/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Writeback has been recently converted to use workqueue instead of its private thread pool implementation. One negative side effect of this conversion is that there's no easy to tell which backing device a writeback work item was working on at the time of task dump, be it sysrq-t, BUG, WARN or whatever, which, according to our writeback brethren, is important in tracking down issues with a lot of mounted file systems on a lot of different devices. This patch restores that information using the new worker description facility. bdi_writeback_workfn() calls set_work_desc() to identify which bdi it's working on. The description is printed out together with the worqueue name and worker function as in the following example dump. WARNING: at fs/fs-writeback.c:1015 bdi_writeback_workfn+0x2b4/0x3c0() Modules linked in: Pid: 28, comm: kworker/u18:0 Not tainted 3.9.0-rc1-work+ #24 empty empty/S3992 Workqueue: writeback bdi_writeback_workfn (flush-8:16) ffffffff820a3a98 ffff88015b927cb8 ffffffff81c61855 ffff88015b927cf8 ffffffff8108f500 0000000000000000 ffff88007a171948 ffff88007a1716b0 ffff88015b49df00 ffff88015b8d3940 0000000000000000 ffff88015b927d08 Call Trace: [<ffffffff81c61855>] dump_stack+0x19/0x1b [<ffffffff8108f500>] warn_slowpath_common+0x70/0xa0 [<ffffffff8108f54a>] warn_slowpath_null+0x1a/0x20 [<ffffffff81200144>] bdi_writeback_workfn+0x2b4/0x3c0 [<ffffffff810b4c87>] process_one_work+0x1d7/0x660 [<ffffffff810b5c72>] worker_thread+0x122/0x380 [<ffffffff810bdfea>] kthread+0xea/0xf0 [<ffffffff81c6cedc>] ret_from_fork+0x7c/0xb0 Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Dave Chinner <david@fromorbit.com> Cc: Jan Kara <jack@suse.cz> Cc: Jens Axboe <axboe@kernel.dk> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Ingo Molnar <mingo@redhat.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>
* Merge tag 'writeback-fixes' of ↵Linus Torvalds2013-02-281-24/+20
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux Pull writeback fixes from Wu Fengguang: "Two writeback fixes - fix negative (setpoint - dirty) in 32bit archs - use down_read_trylock() in writeback_inodes_sb(_nr)_if_idle()" * tag 'writeback-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux: Negative (setpoint-dirty) in bdi_position_ratio() vfs: re-implement writeback_inodes_sb(_nr)_if_idle() and rename them
| * vfs: re-implement writeback_inodes_sb(_nr)_if_idle() and rename themMiao Xie2013-01-121-24/+20
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | writeback_inodes_sb(_nr)_if_idle() is re-implemented by replacing down_read() with down_read_trylock() because - If ->s_umount is write locked, then the sb is not idle. That is writeback_inodes_sb(_nr)_if_idle() needn't wait for the lock. - writeback_inodes_sb(_nr)_if_idle() grabs s_umount lock when it want to start writeback, it may bring us deadlock problem when doing umount. In order to fix the problem, ext4 and btrfs implemented their own writeback functions instead of writeback_inodes_sb(_nr)_if_idle(), but it introduced the redundant code, it is better to implement a new writeback_inodes_sb(_nr)_if_idle(). The name of these two functions is cumbersome, so rename them to try_to_writeback_inodes_sb(_nr). This idea came from Christoph Hellwig. Some code is from the patch of Kamal Mostafa. Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Miao Xie <miaox@cn.fujitsu.com> Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
* | writeback: add more tracepointsTejun Heo2013-01-141-2/+14
|/ | | | | | | | | | | | | | | | | | | | | | | Add tracepoints for page dirtying, writeback_single_inode start, inode dirtying and writeback. For the latter two inode events, a pair of events are defined to denote start and end of the operations (the starting one has _start suffix and the one w/o suffix happens after the operation is complete). These inode ops are FS specific and can be non-trivial and having enclosing tracepoints is useful for external tracers. This is part of tracepoint additions to improve visiblity into dirtying / writeback operations for io tracer and userland. v2: writeback_dirty_inode[_start] TPs may be called for files on pseudo FSes w/ unregistered bdi. Check whether bdi->dev is %NULL before dereferencing. v3: buffer dirtying moved to a block TP. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Jens Axboe <axboe@kernel.dk>
* writeback: fix a typo in commentYan Hong2012-12-121-1/+1
| | | | | | Signed-off-by: Yan Hong <clouds.yan@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* writeback: put unused inodes to LRU after writeback completionJan Kara2012-11-261-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit 169ebd90131b ("writeback: Avoid iput() from flusher thread") removed iget-iput pair from inode writeback. As a side effect, inodes that are dirty during iput_final() call won't be ever added to inode LRU (iput_final() doesn't add dirty inodes to LRU and later when the inode is cleaned there's noone to add the inode there). Thus inodes are effectively unreclaimable until someone looks them up again. The practical effect of this bug is limited by the fact that inodes are pinned by a dentry for long enough that the inode gets cleaned. But still the bug can have nasty consequences leading up to OOM conditions under certain circumstances. Following can easily reproduce the problem: for (( i = 0; i < 1000; i++ )); do mkdir $i for (( j = 0; j < 1000; j++ )); do touch $i/$j echo 2 > /proc/sys/vm/drop_caches done done then one needs to run 'sync; ls -lR' to make inodes reclaimable again. We fix the issue by inserting unused clean inodes into the LRU after writeback finishes in inode_sync_complete(). Signed-off-by: Jan Kara <jack@suse.cz> Reported-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Cc: Wu Fengguang <fengguang.wu@intel.com> Cc: Dave Chinner <david@fromorbit.com> Cc: <stable@vger.kernel.org> [3.5+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* Merge branch 'writeback-for-next' of ↵Linus Torvalds2012-10-121-1/+1
|\ | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux Pull writeback fixes from Fengguang Wu: "Three trivial writeback fixes" * 'writeback-for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux: CPU hotplug, writeback: Don't call writeback_set_ratelimit() too often during hotplug writeback: correct comment for move_expired_inodes() backing-dev: use kstrto* in preference to simple_strtoul
| * writeback: correct comment for move_expired_inodes()Wang Sheng-Hui2012-09-111-1/+1
| | | | | | | | | | | | | | | | | | | | The function scans @delaying_queue and stops at the first inode whose dirtied_when is after *work->older_than_this. So the expired ones being moved are those before *work->older_than_this. Correct the comment here. Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>
* | fs/fs-writeback.c: remove unneccesary parameter of __writeback_single_inode()Yan Hong2012-10-091-4/+3
| | | | | | | | | | | | | | | | | | The parameter 'wb' is never used in this function. Signed-off-by: Yan Hong <clouds.yan@gmail.com> Acked-by: Wu Fengguang <fengguang.wu@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | Merge tag 'ext4_for_linus' of ↵Linus Torvalds2012-10-081-0/+1
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4 Pull ext4 updates from Ted Ts'o: "The big new feature added this time is supporting online resizing using the meta_bg feature. This allows us to resize file systems which are greater than 16TB. In addition, the speed of online resizing has been improved in general. We also fix a number of races, some of which could lead to deadlocks, in ext4's Asynchronous I/O and online defrag support, thanks to good work by Dmitry Monakhov. There are also a large number of more minor bug fixes and cleanups from a number of other ext4 contributors, quite of few of which have submitted fixes for the first time." * tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (69 commits) ext4: fix ext4_flush_completed_IO wait semantics ext4: fix mtime update in nodelalloc mode ext4: fix ext_remove_space for punch_hole case ext4: punch_hole should wait for DIO writers ext4: serialize truncate with owerwrite DIO workers ext4: endless truncate due to nonlocked dio readers ext4: serialize unlocked dio reads with truncate ext4: serialize dio nonlocked reads with defrag workers ext4: completed_io locking cleanup ext4: fix unwritten counter leakage ext4: give i_aiodio_unwritten a more appropriate name ext4: ext4_inode_info diet ext4: convert to use leXX_add_cpu() ext4: ext4_bread usage audit fs: reserve fallocate flag codepoint ext4: remove redundant offset check in mext_check_arguments() ext4: don't clear orphan list on ro mount with errors jbd2: fix assertion failure in commit code due to lacking transaction credits ext4: release donor reference when EXT4_IOC_MOVE_EXT ioctl fails ext4: enable FITRIM ioctl on bigalloc file system ...
| * | ext4: fix potential deadlock in ext4_nonda_switch()Theodore Ts'o2012-09-191-0/+1
| |/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In ext4_nonda_switch(), if the file system is getting full we used to call writeback_inodes_sb_if_idle(). The problem is that we can be holding i_mutex already, and this causes a potential deadlock when writeback_inodes_sb_if_idle() when it tries to take s_umount. (See lockdep output below). As it turns out we don't need need to hold s_umount; the fact that we are in the middle of the write(2) system call will keep the superblock pinned. Unfortunately writeback_inodes_sb() checks to make sure s_umount is taken, and the VFS uses a different mechanism for making sure the file system doesn't get unmounted out from under us. The simplest way of dealing with this is to just simply grab s_umount using a trylock, and skip kicking the writeback flusher thread in the very unlikely case that we can't take a read lock on s_umount without blocking. Also, we now check the cirteria for kicking the writeback thread before we decide to whether to fall back to non-delayed writeback, so if there are any outstanding delayed allocation writes, we try to get them resolved as soon as possible. [ INFO: possible circular locking dependency detected ] 3.6.0-rc1-00042-gce894ca #367 Not tainted ------------------------------------------------------- dd/8298 is trying to acquire lock: (&type->s_umount_key#18){++++..}, at: [<c02277d4>] writeback_inodes_sb_if_idle+0x28/0x46 but task is already holding lock: (&sb->s_type->i_mutex_key#8){+.+...}, at: [<c01ddcce>] generic_file_aio_write+0x5f/0xd3 which lock already depends on the new lock. 2 locks held by dd/8298: #0: (sb_writers#2){.+.+.+}, at: [<c01ddcc5>] generic_file_aio_write+0x56/0xd3 #1: (&sb->s_type->i_mutex_key#8){+.+...}, at: [<c01ddcce>] generic_file_aio_write+0x5f/0xd3 stack backtrace: Pid: 8298, comm: dd Not tainted 3.6.0-rc1-00042-gce894ca #367 Call Trace: [<c015b79c>] ? console_unlock+0x345/0x372 [<c06d62a1>] print_circular_bug+0x190/0x19d [<c019906c>] __lock_acquire+0x86d/0xb6c [<c01999db>] ? mark_held_locks+0x5c/0x7b [<c0199724>] lock_acquire+0x66/0xb9 [<c02277d4>] ? writeback_inodes_sb_if_idle+0x28/0x46 [<c06db935>] down_read+0x28/0x58 [<c02277d4>] ? writeback_inodes_sb_if_idle+0x28/0x46 [<c02277d4>] writeback_inodes_sb_if_idle+0x28/0x46 [<c026f3b2>] ext4_nonda_switch+0xe1/0xf4 [<c0271ece>] ext4_da_write_begin+0x27/0x193 [<c01dcdb0>] generic_file_buffered_write+0xc8/0x1bb [<c01ddc47>] __generic_file_aio_write+0x1dd/0x205 [<c01ddce7>] generic_file_aio_write+0x78/0xd3 [<c026d336>] ext4_file_write+0x480/0x4a6 [<c0198c1d>] ? __lock_acquire+0x41e/0xb6c [<c0180944>] ? sched_clock_cpu+0x11a/0x13e [<c01967e9>] ? trace_hardirqs_off+0xb/0xd [<c018099f>] ? local_clock+0x37/0x4e [<c0209f2c>] do_sync_write+0x67/0x9d [<c0209ec5>] ? wait_on_retry_sync_kiocb+0x44/0x44 [<c020a7b9>] vfs_write+0x7b/0xe6 [<c020a9a6>] sys_write+0x3b/0x64 [<c06dd4bd>] syscall_call+0x7/0xb Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Cc: stable@vger.kernel.org
* | Merge branch 'for-linus' of ↵Linus Torvalds2012-10-011-4/+0
|\ \ | |/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial Pull the trivial tree from Jiri Kosina: "Tiny usual fixes all over the place" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial: (34 commits) doc: fix old config name of kprobetrace fs/fs-writeback.c: cleanup riteback_sb_inodes kerneldoc btrfs: fix the commment for the action flags in delayed-ref.h btrfs: fix trivial typo for the comment of BTRFS_FREE_INO_OBJECTID vfs: fix kerneldoc for generic_fh_to_parent() treewide: fix comment/printk/variable typos ipr: fix small coding style issues doc: fix broken utf8 encoding nfs: comment fix platform/x86: fix asus_laptop.wled_type module parameter mfd: printk/comment fixes doc: getdelays.c: remember to close() socket on error in create_nl_socket() doc: aliasing-test: close fd on write error mmc: fix comment typos dma: fix comments spi: fix comment/printk typos in spi Coccinelle: fix typo in memdup_user.cocci tmiofb: missing NULL pointer checks tools: perf: Fix typo in tools/perf tools/testing: fix comment / output typos ...
| * fs/fs-writeback.c: cleanup riteback_sb_inodes kerneldocLiu Bo2012-09-211-4/+0
| | | | | | | | | | | | | | Argument @only_this_sb has been removed. Signed-off-by: Liu Bo <liub.liubo@gmail.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
* | mm: prepare for removal of obsolete /proc/sys/vm/nr_pdflush_threadsWanpeng Li2012-07-311-5/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | Since per-BDI flusher threads were introduced in 2.6, the pdflush mechanism is not used any more. But the old interface exported through /proc/sys/vm/nr_pdflush_threads still exists and is obviously useless. For back-compatibility, printk warning information and return 2 to notify the users that the interface is removed. Signed-off-by: Wanpeng Li <liwp@linux.vnet.ibm.com> Cc: Wu Fengguang <fengguang.wu@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | Merge tag 'writeback-proportions' of ↵Linus Torvalds2012-07-301-2/+2
|\ \ | |/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux Pull writeback updates from Wu Fengguang: "Use time based periods to age the writeback proportions, which can adapt equally well to fast/slow devices." Fix up trivial conflict in comment in fs/sync.c * tag 'writeback-proportions' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux: writeback: Fix some comment errors block: Convert BDI proportion calculations to flexible proportions lib: Fix possible deadlock in flexible proportion code lib: Proportions with flexible period
| * writeback: Fix some comment errorsWanpeng Li2012-06-091-2/+2
| | | | | | | | | | Signed-off-by: Wanpeng Li <liwp@linux.vnet.ibm.com> Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
* | vfs: Move noop_backing_dev_info check from sync into writebackJan Kara2012-07-221-0/+5
|/ | | | | | | | | | | In principle, a filesystem may want to have ->sync_fs() called during sync(1) although it does not have a bdi (i.e. s_bdi is set to noop_backing_dev_info). Only writeback code really needs bdi set to something reasonable. So move the checks where they are more logical. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* writeback: Fix lock imbalance in writeback_sb_inodes()Jan Kara2012-06-091-0/+1
| | | | | | | | | | | | | | | | | | | | | | | Fix bug introduced by 169ebd90. We have to have wb_list_lock locked when restarting writeback loop after having waited for inode writeback. Bug description by Ted Tso: I can reproduce this fairly easily by using ext4 w/o a journal, running under KVM with 1024megs memory, with fsstress (xfstests #13): [ 45.153294] ===================================== [ 45.154784] [ BUG: bad unlock balance detected! ] [ 45.155591] 3.5.0-rc1-00002-gb22b1f1 #124 Not tainted [ 45.155591] ------------------------------------- [ 45.155591] flush-254:16/2499 is trying to release lock (&(&wb->list_lock)->rlock) at: [ 45.155591] [<c022c3da>] writeback_sb_inodes+0x160/0x327 [ 45.155591] but there are no more locks to release! Reported-by: Theodore Ts'o <tytso@mit.edu> Tested-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
* writeback: Avoid iput() from flusher threadJan Kara2012-05-061-13/+53
| | | | | | | | | | | | | | | | | | | | | Doing iput() from flusher thread (writeback_sb_inodes()) can create problems because iput() can do a lot of work - for example truncate the inode if it's the last iput on unlinked file. Some filesystems depend on flusher thread progressing (e.g. because they need to flush delay allocated blocks to reduce allocation uncertainty) and so flusher thread doing truncate creates interesting dependencies and possibilities for deadlocks. We get rid of iput() in flusher thread by using the fact that I_SYNC inode flag effectively pins the inode in memory. So if we take care to either hold i_lock or have I_SYNC set, we can get away without taking inode reference in writeback_sb_inodes(). As a side effect of these changes, we also fix possible use-after-free in wb_writeback() because inode_wait_for_writeback() call could try to reacquire i_lock on the inode that was already free. Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
* writeback: Refactor writeback_single_inode()Jan Kara2012-05-061-56/+86
| | | | | | | | | | | | | | | | | | | The code in writeback_single_inode() is relatively complex. The list requeing logic makes sense only for flusher thread but not really for sync_inode() or write_inode_now() callers. Also when we want to get rid of inode references held by flusher thread, we will need a special I_SYNC handling there. So separate part of writeback_single_inode() which does the real writeback work into __writeback_single_inode() and make writeback_single_inode() do only stuff necessary for callers writing only one inode, moving the special list handling into writeback_sb_inodes(). As a sideeffect this fixes a possible race where we could skip some inode during sync(2) because other writer refiled it from b_io to b_dirty list. Also I_SYNC handling is moved into the callers of __writeback_single_inode() to make locking easier. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
* writeback: Remove wb->list_lock from writeback_single_inode()Jan Kara2012-05-061-10/+7
| | | | | | | | | | | | | | | | writeback_single_inode() doesn't need wb->list_lock for anything on entry now. So remove the requirement. This makes locking of writeback_single_inode() temporarily awkward (entering with i_lock, returning with i_lock and wb->list_lock) but it will be sanitized in the next patch. Also inode_wait_for_writeback() doesn't need wb->list_lock for anything. It was just taking it to make usage convenient for callers but with writeback_single_inode() changing it's not very convenient anymore. So remove the lock from that function. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
* writeback: Separate inode requeueing after writebackJan Kara2012-05-061-47/+55
| | | | | | | | | Move inode requeueing after inode has been written out into a separate function. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
* writeback: Move I_DIRTY_PAGES handlingJan Kara2012-05-061-2/+3
| | | | | | | | | | | | | | Instead of clearing I_DIRTY_PAGES and resetting it when we didn't succeed in writing them all, just clear the bit only when we succeeded writing all the pages. We also move the clearing of the bit close to other i_state handling to separate it from writeback list handling. This is desirable because list handling will differ for flusher thread and other writeback_single_inode() callers in future. No filesystem plays any tricks with I_DIRTY_PAGES (like checking it in ->writepages or ->write_inode implementation) so this movement is safe. Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
* writeback: Move requeueing when I_SYNC set to writeback_sb_inodes()Jan Kara2012-05-061-14/+16
| | | | | | | | | | | | | | When writeback_single_inode() is called on inode which has I_SYNC already set while doing WB_SYNC_NONE, inode is moved to b_more_io list. However this makes sense only if the caller is flusher thread. For other callers of writeback_single_inode() it doesn't really make sense and may be even wrong - flusher thread may be doing WB_SYNC_ALL writeback in parallel. So we move requeueing from writeback_single_inode() to writeback_sb_inodes(). Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
* writeback: Move clearing of I_SYNC into inode_sync_complete()Jan Kara2012-05-061-6/+2
| | | | | | | | | | | | Move clearing of I_SYNC into inode_sync_complete(). It is more logical to have clearing of I_SYNC bit and waking of waiters in one place. Also later we will have two places needing to clear I_SYNC and wake up waiters so this allows them to use the common helper. Moving of I_SYNC clearing to a later stage of writeback_single_inode() is safe since we hold i_lock all the time. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
* Merge tag 'writeback-fixes' of ↵Linus Torvalds2012-03-281-20/+2
|\ | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux Pull trivial writeback fixes from Wu Fengguang: "They've been tested in linux-next for 20 days actually." * tag 'writeback-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux: writeback: Remove outdated comment fs: Remove bogus wait in write_inode_now()
| * writeback: Remove outdated commentJan Kara2012-03-211-18/+2
| | | | | | | | | | | | | | | | | | | | | | | | The comment is hopelessly outdated and misplaced. We no longer have 'bdi' part of writeback work, the comment about blockdev super is outdated, comment about throttling as well. Information about list handling is in more detail at queue_io(). So just move the bit about older_than_this to close to move_expired_inodes() and remove the rest. Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
| * fs: Remove bogus wait in write_inode_now()Jan Kara2012-03-211-2/+0
| | | | | | | | | | | | | | | | | | | | | | | | inode_sync_wait() in write_inode_now() is just bogus. That function waits for I_SYNC bit to be cleared but writeback_single_inode() clears the bit on return so the wait is effectivelly a nop unless someone else submits the inode for writeback again. All the waiting write_inode_now() needs is achieved by using WB_SYNC_ALL writeback mode. Signed-off-by: Jan Kara <jack@suse.cz> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
* | Merge tag 'module-for-3.4' of ↵Linus Torvalds2012-03-241-1/+1
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux Pull cleanup of fs/ and lib/ users of module.h from Paul Gortmaker: "Fix up files in fs/ and lib/ dirs to only use module.h if they really need it. These are trivial in scope vs the work done previously. We now have things where any few remaining cleanups can be farmed out to arch or subsystem maintainers, and I have done so when possible. What is remaining here represents the bits that don't clearly lie within a single arch/subsystem boundary, like the fs dir and the lib dir. Some duplicate includes arising from overlapping fixes from independent subsystem maintainer submissions are also quashed." Fix up trivial conflicts due to clashes with other include file cleanups (including some due to the previous bug.h cleanup pull). * tag 'module-for-3.4' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux: lib: reduce the use of module.h wherever possible fs: reduce the use of module.h wherever possible includecheck: delete any duplicate instances of module.h
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