kernel.git/fs/btrfs/raid56.c, branch linux-3.17.y

Btrfs: fix task hang under heavy compressed write

2014-08-24T14:17:02Z

This has been reported and discussed for a long time, and this hang occurs in both 3.15 and 3.16. Btrfs now migrates to use kernel workqueue, but it introduces this hang problem. Btrfs has a kind of work queued as an ordered way, which means that its ordered_func() must be processed in the way of FIFO, so it usually looks like -- normal_work_helper(arg) work = container_of(arg, struct btrfs_work, normal_work); work->func() <---- (we name it work X) for ordered_work in wq->ordered_list ordered_work->ordered_func() ordered_work->ordered_free() The hang is a rare case, first when we find free space, we get an uncached block group, then we go to read its free space cache inode for free space information, so it will file a readahead request btrfs_readpages() for page that is not in page cache __do_readpage() submit_extent_page() btrfs_submit_bio_hook() btrfs_bio_wq_end_io() submit_bio() end_workqueue_bio() <--(ret by the 1st endio) queue a work(named work Y) for the 2nd also the real endio() So the hang occurs when work Y's work_struct and work X's work_struct happens to share the same address. A bit more explanation, A,B,C -- struct btrfs_work arg -- struct work_struct kthread: worker_thread() pick up a work_struct from @worklist process_one_work(arg) worker->current_work = arg; <-- arg is A->normal_work worker->current_func(arg) normal_work_helper(arg) A = container_of(arg, struct btrfs_work, normal_work); A->func() A->ordered_func() A->ordered_free() <-- A gets freed B->ordered_func() submit_compressed_extents() find_free_extent() load_free_space_inode() ... <-- (the above readhead stack) end_workqueue_bio() btrfs_queue_work(work C) B->ordered_free() As if work A has a high priority in wq->ordered_list and there are more ordered works queued after it, such as B->ordered_func(), its memory could have been freed before normal_work_helper() returns, which means that kernel workqueue code worker_thread() still has worker->current_work pointer to be work A->normal_work's, ie. arg's address. Meanwhile, work C is allocated after work A is freed, work C->normal_work and work A->normal_work are likely to share the same address(I confirmed this with ftrace output, so I'm not just guessing, it's rare though). When another kthread picks up work C->normal_work to process, and finds our kthread is processing it(see find_worker_executing_work()), it'll think work C as a collision and skip then, which ends up nobody processing work C. So the situation is that our kthread is waiting forever on work C. Besides, there're other cases that can lead to deadlock, but the real problem is that all btrfs workqueue shares one work->func, -- normal_work_helper, so this makes each workqueue to have its own helper function, but only a wraper pf normal_work_helper. With this patch, I no long hit the above hang. Signed-off-by: Liu Bo Signed-off-by: Chris Mason

Btrfs: fix crash when mounting raid5 btrfs with missing disks

2014-06-28T20:48:45Z

The reproducer is $ mkfs.btrfs D1 D2 D3 -mraid5 $ mkfs.ext4 D2 && mkfs.ext4 D3 $ mount D1 /btrfs -odegraded ------------------- [ 87.672992] ------------[ cut here ]------------ [ 87.673845] kernel BUG at fs/btrfs/raid56.c:1828! ... [ 87.673845] RIP: 0010:[] [] __raid_recover_end_io+0x4ae/0x4d0 ... [ 87.673845] Call Trace: [ 87.673845] [] ? mempool_free+0x36/0xa0 [ 87.673845] [] raid_recover_end_io+0x75/0xa0 [ 87.673845] [] bio_endio+0x5b/0xa0 [ 87.673845] [] bio_endio_nodec+0x12/0x20 [ 87.673845] [] end_workqueue_fn+0x41/0x50 [ 87.673845] [] normal_work_helper+0xca/0x2c0 [ 87.673845] [] process_one_work+0x1eb/0x530 [ 87.673845] [] ? process_one_work+0x189/0x530 [ 87.673845] [] worker_thread+0x11b/0x4f0 [ 87.673845] [] ? rescuer_thread+0x290/0x290 [ 87.673845] [] kthread+0xe4/0x100 [ 87.673845] [] ? kthread_create_on_node+0x220/0x220 [ 87.673845] [] ret_from_fork+0x7c/0xb0 [ 87.673845] [] ? kthread_create_on_node+0x220/0x220 ------------------- It's because that we miscalculate @rbio->bbio->error so that it doesn't reach maximum of tolerable errors while it should have. Signed-off-by: Liu Bo Tested-by: Satoru Takeuchi Signed-off-by: Chris Mason

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs

2014-04-04T22:31:36Z

Pull btrfs changes from Chris Mason: "This is a pretty long stream of bug fixes and performance fixes. Qu Wenruo has replaced the btrfs async threads with regular kernel workqueues. We'll keep an eye out for performance differences, but it's nice to be using more generic code for this. We still have some corruption fixes and other patches coming in for the merge window, but this batch is tested and ready to go" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs: (108 commits) Btrfs: fix a crash of clone with inline extents's split btrfs: fix uninit variable warning Btrfs: take into account total references when doing backref lookup Btrfs: part 2, fix incremental send's decision to delay a dir move/rename Btrfs: fix incremental send's decision to delay a dir move/rename Btrfs: remove unnecessary inode generation lookup in send Btrfs: fix race when updating existing ref head btrfs: Add trace for btrfs_workqueue alloc/destroy Btrfs: less fs tree lock contention when using autodefrag Btrfs: return EPERM when deleting a default subvolume Btrfs: add missing kfree in btrfs_destroy_workqueue Btrfs: cache extent states in defrag code path Btrfs: fix deadlock with nested trans handles Btrfs: fix possible empty list access when flushing the delalloc inodes Btrfs: split the global ordered extents mutex Btrfs: don't flush all delalloc inodes when we doesn't get s_umount lock Btrfs: reclaim delalloc metadata more aggressively Btrfs: remove unnecessary lock in may_commit_transaction() Btrfs: remove the unnecessary flush when preparing the pages Btrfs: just do dirty page flush for the inode with compression before direct IO ...

btrfs: Cleanup the "_struct" suffix in btrfs_workequeue

2014-03-10T19:17:16Z

Since the "_struct" suffix is mainly used for distinguish the differnt btrfs_work between the original and the newly created one, there is no need using the suffix since all btrfs_workers are changed into btrfs_workqueue. Also this patch fixed some codes whose code style is changed due to the too long "_struct" suffix. Signed-off-by: Qu Wenruo Tested-by: David Sterba Signed-off-by: Josef Bacik

btrfs: Replace fs_info->rmw_workers workqueue with btrfs_workqueue.

2014-03-10T19:17:09Z

Replace the fs_info->rmw_workers with the newly created btrfs_workqueue. Signed-off-by: Qu Wenruo Tested-by: David Sterba Signed-off-by: Josef Bacik

block: Abstract out bvec iterator

2013-11-24T06:33:47Z

Immutable biovecs are going to require an explicit iterator. To implement immutable bvecs, a later patch is going to add a bi_bvec_done member to this struct; for now, this patch effectively just renames things. Signed-off-by: Kent Overstreet Cc: Jens Axboe Cc: Geert Uytterhoeven Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: "Ed L. Cashin" Cc: Nick Piggin Cc: Lars Ellenberg Cc: Jiri Kosina Cc: Matthew Wilcox Cc: Geoff Levand Cc: Yehuda Sadeh Cc: Sage Weil Cc: Alex Elder Cc: ceph-devel@vger.kernel.org Cc: Joshua Morris Cc: Philip Kelleher Cc: Rusty Russell Cc: "Michael S. Tsirkin" Cc: Konrad Rzeszutek Wilk Cc: Jeremy Fitzhardinge Cc: Neil Brown Cc: Alasdair Kergon Cc: Mike Snitzer Cc: dm-devel@redhat.com Cc: Martin Schwidefsky Cc: Heiko Carstens Cc: linux390@de.ibm.com Cc: Boaz Harrosh Cc: Benny Halevy Cc: "James E.J. Bottomley" Cc: Greg Kroah-Hartman Cc: "Nicholas A. Bellinger" Cc: Alexander Viro Cc: Chris Mason Cc: "Theodore Ts'o" Cc: Andreas Dilger Cc: Jaegeuk Kim Cc: Steven Whitehouse Cc: Dave Kleikamp Cc: Joern Engel Cc: Prasad Joshi Cc: Trond Myklebust Cc: KONISHI Ryusuke Cc: Mark Fasheh Cc: Joel Becker Cc: Ben Myers Cc: xfs@oss.sgi.com Cc: Steven Rostedt Cc: Frederic Weisbecker Cc: Ingo Molnar Cc: Len Brown Cc: Pavel Machek Cc: "Rafael J. Wysocki" Cc: Herton Ronaldo Krzesinski Cc: Ben Hutchings Cc: Andrew Morton Cc: Guo Chao Cc: Tejun Heo Cc: Asai Thambi S P Cc: Selvan Mani Cc: Sam Bradshaw Cc: Wei Yongjun Cc: "Roger Pau Monné" Cc: Jan Beulich Cc: Stefano Stabellini Cc: Ian Campbell Cc: Sebastian Ott Cc: Christian Borntraeger Cc: Minchan Kim Cc: Jiang Liu Cc: Nitin Gupta Cc: Jerome Marchand Cc: Joe Perches Cc: Peng Tao Cc: Andy Adamson Cc: fanchaoting Cc: Jie Liu Cc: Sunil Mushran Cc: "Martin K. Petersen" Cc: Namjae Jeon Cc: Pankaj Kumar Cc: Dan Magenheimer Cc: Mel Gorman 6

btrfs: remove fs/btrfs/compat.h

2013-11-12T03:03:19Z

fs/btrfs/compat.h only contained trivial macro wrappers of drop_nlink() and inc_nlink(). This doesn't belong in mainline. Signed-off-by: Zach Brown Signed-off-by: Josef Bacik Signed-off-by: Chris Mason

Btrfs, raid56: fix memory leak when allocating pages for p/q stripes failed

2013-09-01T12:04:27Z

Signed-off-by: Miao Xie Signed-off-by: Josef Bacik Signed-off-by: Chris Mason

btrfs/raid56: fix and cleanup some error paths

2013-09-01T12:04:26Z

The alloc_rbio() frees "raid_map" and "bbio" on error, so there is a potential double free bug in raid56_parity_write(). The raid56_parity_write() and raid56_parity_recover() functions should still free "raid_map" and "bbio" on error if other errors occur though, so I have added some more calls to kfree(). Signed-off-by: Dan Carpenter Reviewed-by: Miao Xie Signed-off-by: Josef Bacik Signed-off-by: Chris Mason

Btrfs: use a btrfs bioset instead of abusing bio internals

2013-05-18T01:52:52Z

Btrfs has been pointer tagging bi_private and using bi_bdev to store the stripe index and mirror number of failed IOs. As bios bubble back up through the call chain, we use these to decide if and how to retry our IOs. They are also used to count IO failures on a per device basis. Recently a bio tracepoint was added lead to crashes because we were abusing bi_bdev. This commit adds a btrfs bioset, and creates explicit fields for the mirror number and stripe index. The plan is to extend this structure for all of the fields currently in struct btrfs_bio, which will mean one less kmalloc in our IO path. Signed-off-by: Chris Mason Reported-by: Tejun Heo