Hello, Here is the v2 patch for fixing a dead loop issue at xfs_vm_writepage() which has been reported by Michael a few months ago. I have ran all those generic as well as xfs specified tests via xfstests, it works fine to me. The original thread can be found at: http://oss.sgi.com/archives/xfs/2013-07/msg00154.html Sorry for the delay as I have spent all the time to backport upstream changes in the past few weeks. Thanks, -Jeff From: Jie Liu <jeff.liu@xxxxxxxxxx> Write a file with an offset greater than 16TB on 32-bit system and then trigger page write-back via sync(1) as below will cause the task hang in a little while: # block_size=4096 # offset=$(((2**32 - 1) * $block_size)) # xfs_io -f -c "pwrite $offset $block_size" /storage/test_file # sync INFO: task sync:2590 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. sync D c1064a28 0 2590 2097 0x00000000 ..... Call Trace: [<c1064a28>] ? ttwu_do_wakeup+0x18/0x130 [<c1066d0e>] ? try_to_wake_up+0x1ce/0x220 [<c1066dbf>] ? wake_up_process+0x1f/0x40 [<c104fc2e>] ? wake_up_worker+0x1e/0x30 [<c15b6083>] schedule+0x23/0x60 [<c15b3c2d>] schedule_timeout+0x18d/0x1f0 [<c12a143e>] ? do_raw_spin_unlock+0x4e/0x90 [<c10515f1>] ? __queue_delayed_work+0x91/0x150 [<c12a12ef>] ? do_raw_spin_lock+0x3f/0x100 [<c12a143e>] ? do_raw_spin_unlock+0x4e/0x90 [<c15b5b5d>] wait_for_completion+0x7d/0xc0 [<c1066d60>] ? try_to_wake_up+0x220/0x220 [<c116a4d2>] sync_inodes_sb+0x92/0x180 [<c116fb05>] sync_inodes_one_sb+0x15/0x20 [<c114a8f8>] iterate_supers+0xb8/0xc0 [<c116faf0>] ? fdatawrite_one_bdev+0x20/0x20 [<c116fc21>] sys_sync+0x31/0x80 [<c15be18d>] sysenter_do_call+0x12/0x28 The reason is that the end_index is unsigned long with maximum value '2^32-1=4294967295' on 32-bit platform, and the given offset cause it wrapped to 0, so that the following codes will repeat again and again until the task schedule time out: end_index = offset >> PAGE_CACHE_SHIFT; last_index = (offset - 1) >> PAGE_CACHE_SHIFT; if (page->index >= end_index) { unsigned offset_into_page = offset & (PAGE_CACHE_SIZE - 1); /* * Just skip the page if it is fully outside i_size, e.g. due * to a truncate operation that is in progress. */ if (page->index >= end_index + 1 || offset_into_page == 0) { ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ unlock_page(page); return 0; } To check a page is fully outsids i_size or not, we can change the logic to: if (page->index > end_index || (page->index == end_index && offset_into_page == 0)) Secondly, there still has another similar issue when calculating the end offset for mapping the filesystem blocks to the file blocks for delalloc. With the same tests to above, run unmount(8) will cause kernel panic if CONFIG_XFS_DEBUG is enabled: XFS: Assertion failed: XFS_FORCED_SHUTDOWN(ip->i_mount) || \ ip->i_delayed_blks == 0, file: fs/xfs/xfs_super.c, line: 964 kernel BUG at fs/xfs/xfs_message.c:108! invalid opcode: 0000 [#1] SMP task: edddc100 ti: ec6ee000 task.ti: ec6ee000 EIP: 0060:[<f83d87cb>] EFLAGS: 00010296 CPU: 1 EIP is at assfail+0x2b/0x30 [xfs] .............. Call Trace: [<f83d9cd4>] xfs_fs_destroy_inode+0x74/0x120 [xfs] [<c115ddf1>] destroy_inode+0x31/0x50 [<c115deff>] evict+0xef/0x170 [<c115dfb2>] dispose_list+0x32/0x40 [<c115ea3a>] evict_inodes+0xca/0xe0 [<c1149706>] generic_shutdown_super+0x46/0xd0 [<c11497b9>] kill_block_super+0x29/0x70 [<c1149a14>] deactivate_locked_super+0x44/0x70 [<c114a427>] deactivate_super+0x47/0x60 [<c1161c3d>] mntput_no_expire+0xcd/0x120 [<c1162ae8>] SyS_umount+0xa8/0x370 [<c1162dce>] SyS_oldumount+0x1e/0x20 [<c15be18d>] sysenter_do_call+0x12/0x28 That because the end_offset is evaluated to 0 same to above, hence the mapping and covertion for dealloc file blocks to file system blocks did not happened. This patch just fixed both issues. Reported-by: Michael L. Semon <mlsemon35@xxxxxxxxx> Signed-off-by: Jie Liu <jeff.liu@xxxxxxxxxx> --- fs/xfs/xfs_aops.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c index 41a6950..6059d00 100644 --- a/fs/xfs/xfs_aops.c +++ b/fs/xfs/xfs_aops.c @@ -969,7 +969,9 @@ xfs_vm_writepage( offset = i_size_read(inode); end_index = offset >> PAGE_CACHE_SHIFT; last_index = (offset - 1) >> PAGE_CACHE_SHIFT; - if (page->index >= end_index) { + if (page->index < end_index) + end_offset = (xfs_off_t)(page->index + 1) << PAGE_CACHE_SHIFT; + else { unsigned offset_into_page = offset & (PAGE_CACHE_SIZE - 1); /* @@ -978,7 +980,8 @@ xfs_vm_writepage( * page so that reclaim stops reclaiming it. Otherwise * xfs_vm_releasepage() is called on it and gets confused. */ - if (page->index >= end_index + 1 || offset_into_page == 0) + if (page->index > end_index || + (page->index == end_index && offset_into_page == 0)) goto redirty; /* @@ -990,11 +993,9 @@ xfs_vm_writepage( * not written out to the file." */ zero_user_segment(page, offset_into_page, PAGE_CACHE_SIZE); + end_offset = offset; } - end_offset = min_t(unsigned long long, - (xfs_off_t)(page->index + 1) << PAGE_CACHE_SHIFT, - offset); len = 1 << inode->i_blkbits; bh = head = page_buffers(page); -- 1.7.9.5 _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
