diff options
Diffstat (limited to '0003-Btrfs-fix-unwritten-extent-buffers-and-hangs-on-future-writeback-attempts.patch')
| -rw-r--r-- | 0003-Btrfs-fix-unwritten-extent-buffers-and-hangs-on-future-writeback-attempts.patch | 145 |
1 files changed, 0 insertions, 145 deletions
diff --git a/0003-Btrfs-fix-unwritten-extent-buffers-and-hangs-on-future-writeback-attempts.patch b/0003-Btrfs-fix-unwritten-extent-buffers-and-hangs-on-future-writeback-attempts.patch deleted file mode 100644 index b6d19c3..0000000 --- a/0003-Btrfs-fix-unwritten-extent-buffers-and-hangs-on-future-writeback-attempts.patch +++ /dev/null @@ -1,145 +0,0 @@ -From 45fc8773f47b7cbe56caab0e14abf26d1e044e63 Mon Sep 17 00:00:00 2001 -From: Filipe Manana <fdmanana@suse.com> -Date: Wed, 11 Sep 2019 17:42:00 +0100 -Subject: Btrfs: fix unwritten extent buffers and hangs on future writeback - attempts - -The lock_extent_buffer_io() returns 1 to the caller to tell it everything -went fine and the callers needs to start writeback for the extent buffer -(submit a bio, etc), 0 to tell the caller everything went fine but it does -not need to start writeback for the extent buffer, and a negative value if -some error happened. - -When it's about to return 1 it tries to lock all pages, and if a try lock -on a page fails, and we didn't flush any existing bio in our "epd", it -calls flush_write_bio(epd) and overwrites the return value of 1 to 0 or -an error. The page might have been locked elsewhere, not with the goal -of starting writeback of the extent buffer, and even by some code other -than btrfs, like page migration for example, so it does not mean the -writeback of the extent buffer was already started by some other task, -so returning a 0 tells the caller (btree_write_cache_pages()) to not -start writeback for the extent buffer. Note that epd might currently have -either no bio, so flush_write_bio() returns 0 (success) or it might have -a bio for another extent buffer with a lower index (logical address). - -Since we return 0 with the EXTENT_BUFFER_WRITEBACK bit set on the -extent buffer and writeback is never started for the extent buffer, -future attempts to writeback the extent buffer will hang forever waiting -on that bit to be cleared, since it can only be cleared after writeback -completes. Such hang is reported with a trace like the following: - - [49887.347053] INFO: task btrfs-transacti:1752 blocked for more than 122 seconds. - [49887.347059] Not tainted 5.2.13-gentoo #2 - [49887.347060] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. - [49887.347062] btrfs-transacti D 0 1752 2 0x80004000 - [49887.347064] Call Trace: - [49887.347069] ? __schedule+0x265/0x830 - [49887.347071] ? bit_wait+0x50/0x50 - [49887.347072] ? bit_wait+0x50/0x50 - [49887.347074] schedule+0x24/0x90 - [49887.347075] io_schedule+0x3c/0x60 - [49887.347077] bit_wait_io+0x8/0x50 - [49887.347079] __wait_on_bit+0x6c/0x80 - [49887.347081] ? __lock_release.isra.29+0x155/0x2d0 - [49887.347083] out_of_line_wait_on_bit+0x7b/0x80 - [49887.347084] ? var_wake_function+0x20/0x20 - [49887.347087] lock_extent_buffer_for_io+0x28c/0x390 - [49887.347089] btree_write_cache_pages+0x18e/0x340 - [49887.347091] do_writepages+0x29/0xb0 - [49887.347093] ? kmem_cache_free+0x132/0x160 - [49887.347095] ? convert_extent_bit+0x544/0x680 - [49887.347097] filemap_fdatawrite_range+0x70/0x90 - [49887.347099] btrfs_write_marked_extents+0x53/0x120 - [49887.347100] btrfs_write_and_wait_transaction.isra.4+0x38/0xa0 - [49887.347102] btrfs_commit_transaction+0x6bb/0x990 - [49887.347103] ? start_transaction+0x33e/0x500 - [49887.347105] transaction_kthread+0x139/0x15c - -So fix this by not overwriting the return value (ret) with the result -from flush_write_bio(). We also need to clear the EXTENT_BUFFER_WRITEBACK -bit in case flush_write_bio() returns an error, otherwise it will hang -any future attempts to writeback the extent buffer, and undo all work -done before (set back EXTENT_BUFFER_DIRTY, etc). - -This is a regression introduced in the 5.2 kernel. - -Fixes: 2e3c25136adfb ("btrfs: extent_io: add proper error handling to lock_extent_buffer_for_io()") -Fixes: f4340622e0226 ("btrfs: extent_io: Move the BUG_ON() in flush_write_bio() one level up") -Reported-by: Zdenek Sojka <zsojka@seznam.cz> -Link: https://lore.kernel.org/linux-btrfs/GpO.2yos.3WGDOLpx6t%7D.1TUDYM@seznam.cz/T/#u -Reported-by: Stefan Priebe - Profihost AG <s.priebe@profihost.ag> -Link: https://lore.kernel.org/linux-btrfs/5c4688ac-10a7-fb07-70e8-c5d31a3fbb38@profihost.ag/T/#t -Reported-by: Drazen Kacar <drazen.kacar@oradian.com> -Link: https://lore.kernel.org/linux-btrfs/DB8PR03MB562876ECE2319B3E579590F799C80@DB8PR03MB5628.eurprd03.prod.outlook.com/ -Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=204377 -Signed-off-by: Filipe Manana <fdmanana@suse.com> ---- - fs/btrfs/extent_io.c | 35 ++++++++++++++++++++++++++--------- - 1 file changed, 26 insertions(+), 9 deletions(-) - -diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c -index db337e53aab3..93900ff87df7 100644 ---- a/fs/btrfs/extent_io.c -+++ b/fs/btrfs/extent_io.c -@@ -3591,6 +3591,13 @@ void wait_on_extent_buffer_writeback(struct extent_buffer *eb) - TASK_UNINTERRUPTIBLE); - } - -+static void end_extent_buffer_writeback(struct extent_buffer *eb) -+{ -+ clear_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags); -+ smp_mb__after_atomic(); -+ wake_up_bit(&eb->bflags, EXTENT_BUFFER_WRITEBACK); -+} -+ - /* - * Lock eb pages and flush the bio if we can't the locks - * -@@ -3662,8 +3669,11 @@ static noinline_for_stack int lock_extent_buffer_for_io(struct extent_buffer *eb - - if (!trylock_page(p)) { - if (!flush) { -- ret = flush_write_bio(epd); -- if (ret < 0) { -+ int err; -+ -+ err = flush_write_bio(epd); -+ if (err < 0) { -+ ret = err; - failed_page_nr = i; - goto err_unlock; - } -@@ -3678,16 +3688,23 @@ err_unlock: - /* Unlock already locked pages */ - for (i = 0; i < failed_page_nr; i++) - unlock_page(eb->pages[i]); -+ /* -+ * Clear EXTENT_BUFFER_WRITEBACK and wake up anyone waiting on it. -+ * Also set back EXTENT_BUFFER_DIRTY so future attempts to this eb can -+ * be made and undo everything done before. -+ */ -+ btrfs_tree_lock(eb); -+ spin_lock(&eb->refs_lock); -+ set_bit(EXTENT_BUFFER_DIRTY, &eb->bflags); -+ end_extent_buffer_writeback(eb); -+ spin_unlock(&eb->refs_lock); -+ percpu_counter_add_batch(&fs_info->dirty_metadata_bytes, eb->len, -+ fs_info->dirty_metadata_batch); -+ btrfs_clear_header_flag(eb, BTRFS_HEADER_FLAG_WRITTEN); -+ btrfs_tree_unlock(eb); - return ret; - } - --static void end_extent_buffer_writeback(struct extent_buffer *eb) --{ -- clear_bit(EXTENT_BUFFER_WRITEBACK, &eb->bflags); -- smp_mb__after_atomic(); -- wake_up_bit(&eb->bflags, EXTENT_BUFFER_WRITEBACK); --} -- - static void set_btree_ioerr(struct page *page) - { - struct extent_buffer *eb = (struct extent_buffer *)page->private; --- -cgit v1.2.1-1-g437b - |