On 03/23/2016 02:43 PM, Brian Foster wrote: > On Wed, Mar 23, 2016 at 12:15:42PM +0200, Nikolay Borisov wrote: >> Hello, >> >> So I have an XFS filesystem which houses 2 2.3T sparse files, which are >> loop-mounted. Recently I migrated a server to a 4.4.6 kernel and this >> morning I observed the following in my dmesg: >> >> XFS: loop0(15174) possible memory allocation deadlock size 107168 in >> kmem_alloc (mode:0x2400240) >> > > Is there a stack trace associated with this message? > >> the mode is essentially (GFP_KERNEL | GFP_NOWARN) &= ~__GFP_FS. >> Here is the site of the loop file in case it matters: >> >> du -h --apparent-size /storage/loop/file1 >> 2.3T /storage/loop/file1 >> >> du -h /storage/loop/file1 >> 878G /storage/loop/file1 >> >> And this string is repeated multiple times. Looking at the output of >> "echo w > /proc/sysrq-trigger" I see the following suspicious entry: >> >> loop0 D ffff881fe081f038 0 15174 2 0x00000000 >> ffff881fe081f038 ffff883ff29fa700 ffff881fecb70d00 ffff88407fffae00 >> 0000000000000000 0000000502404240 ffffffff81e30d60 0000000000000000 >> 0000000000000000 ffff881f00000003 0000000000000282 ffff883f00000000 >> Call Trace: >> [<ffffffff8163ac01>] ? _raw_spin_lock_irqsave+0x21/0x60 >> [<ffffffff81636fd7>] schedule+0x47/0x90 >> [<ffffffff81639f03>] schedule_timeout+0x113/0x1e0 >> [<ffffffff810ac580>] ? lock_timer_base+0x80/0x80 >> [<ffffffff816363d4>] io_schedule_timeout+0xa4/0x110 >> [<ffffffff8114aadf>] congestion_wait+0x7f/0x130 >> [<ffffffff810939e0>] ? woken_wake_function+0x20/0x20 >> [<ffffffffa0283bac>] kmem_alloc+0x8c/0x120 [xfs] >> [<ffffffff81181751>] ? __kmalloc+0x121/0x250 >> [<ffffffffa0283c73>] kmem_realloc+0x33/0x80 [xfs] >> [<ffffffffa02546cd>] xfs_iext_realloc_indirect+0x3d/0x60 [xfs] >> [<ffffffffa02548cf>] xfs_iext_irec_new+0x3f/0xf0 [xfs] >> [<ffffffffa0254c0d>] xfs_iext_add_indirect_multi+0x14d/0x210 [xfs] >> [<ffffffffa02554b5>] xfs_iext_add+0xc5/0x230 [xfs] > > It looks like it's working to add a new extent to the in-core extent > list. If this is the stack associated with the warning message (combined > with the large alloc size), I wonder if there's a fragmentation issue on > the file leading to an excessive number of extents. Yes this is the stack trace associated. > > What does 'xfs_bmap -v /storage/loop/file1' show? It spews a lot of stuff but here is a summary, more detailed info can be provided if you need it: xfs_bmap -v /storage/loop/file1 | wc -l 900908 xfs_bmap -v /storage/loop/file1 | grep -c hole 94568 Also, what would constitute an "excessive number of extents"? > > Brian > >> [<ffffffff8112b5c5>] ? mempool_alloc_slab+0x15/0x20 >> [<ffffffffa0256269>] xfs_iext_insert+0x59/0x110 [xfs] >> [<ffffffffa0230928>] ? xfs_bmap_add_extent_hole_delay+0xd8/0x740 [xfs] >> [<ffffffffa0230928>] xfs_bmap_add_extent_hole_delay+0xd8/0x740 [xfs] >> [<ffffffff8112b5c5>] ? mempool_alloc_slab+0x15/0x20 >> [<ffffffff8112b725>] ? mempool_alloc+0x65/0x180 >> [<ffffffffa02543d8>] ? xfs_iext_get_ext+0x38/0x70 [xfs] >> [<ffffffffa0254e8d>] ? xfs_iext_bno_to_ext+0xed/0x150 [xfs] >> [<ffffffffa02311b5>] xfs_bmapi_reserve_delalloc+0x225/0x250 [xfs] >> [<ffffffffa023131e>] xfs_bmapi_delay+0x13e/0x290 [xfs] >> [<ffffffffa02730ad>] xfs_iomap_write_delay+0x17d/0x300 [xfs] >> [<ffffffffa022e434>] ? xfs_bmapi_read+0x114/0x330 [xfs] >> [<ffffffffa025ddc5>] __xfs_get_blocks+0x585/0xa90 [xfs] >> [<ffffffff81324b53>] ? __percpu_counter_add+0x63/0x80 >> [<ffffffff811374cd>] ? account_page_dirtied+0xed/0x1b0 >> [<ffffffff811cfc59>] ? alloc_buffer_head+0x49/0x60 >> [<ffffffff811d07c0>] ? alloc_page_buffers+0x60/0xb0 >> [<ffffffff811d13e5>] ? create_empty_buffers+0x45/0xc0 >> [<ffffffffa025e324>] xfs_get_blocks+0x14/0x20 [xfs] >> [<ffffffff811d34e2>] __block_write_begin+0x1c2/0x580 >> [<ffffffffa025e310>] ? xfs_get_blocks_direct+0x20/0x20 [xfs] >> [<ffffffffa025bbb1>] xfs_vm_write_begin+0x61/0xf0 [xfs] >> [<ffffffff81127e50>] generic_perform_write+0xd0/0x1f0 >> [<ffffffffa026a341>] xfs_file_buffered_aio_write+0xe1/0x240 [xfs] >> [<ffffffff812e16d2>] ? bt_clear_tag+0xb2/0xd0 >> [<ffffffffa026ab87>] xfs_file_write_iter+0x167/0x170 [xfs] >> [<ffffffff81199d76>] vfs_iter_write+0x76/0xa0 >> [<ffffffffa03fb735>] lo_write_bvec+0x65/0x100 [loop] >> [<ffffffffa03fd589>] loop_queue_work+0x689/0x924 [loop] >> [<ffffffff8163ba52>] ? retint_kernel+0x10/0x10 >> [<ffffffff81074d71>] kthread_worker_fn+0x61/0x1c0 >> [<ffffffff81074d10>] ? flush_kthread_work+0x120/0x120 >> [<ffffffff81074d10>] ? flush_kthread_work+0x120/0x120 >> [<ffffffff810744d7>] kthread+0xd7/0xf0 >> [<ffffffff8107d22e>] ? schedule_tail+0x1e/0xd0 >> [<ffffffff81074400>] ? kthread_freezable_should_stop+0x80/0x80 >> [<ffffffff8163b2af>] ret_from_fork+0x3f/0x70 >> [<ffffffff81074400>] ? kthread_freezable_should_stop+0x80/0x80 >> >> So this seems that there are writes to the loop device being queued and >> while being served XFS has to do some internal memory allocation to fit >> the new data, however due to some *uknown* reason it fails and starts >> looping in kmem_alloc. I didn't see any OOM reports so presumably the >> server was not out of memory, but unfortunately I didn't check the >> memory fragmentation, though I collected a crash dump in case you need >> further info. >> >> The one thing which bugs me is that XFS tried to allocate 107 contiguous >> kb which is page-order-26 isn't this waaaaay too big and almost never >> satisfiable, despite direct/bg reclaim to be enabled? For now I've >> reverted to using 3.12.52 kernel, where this issue hasn't been observed >> (yet) any ideas would be much appreciated. >> >> _______________________________________________ >> xfs mailing list >> xfs@xxxxxxxxxxx >> http://oss.sgi.com/mailman/listinfo/xfs _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
