--- /dev/null
+From 40cdc509877bacb438213b83c7541c5e24a1d9ec Mon Sep 17 00:00:00 2001
+From: Filipe Manana <fdmanana@suse.com>
+Date: Tue, 18 Jan 2022 13:39:34 +0000
+Subject: btrfs: skip reserved bytes warning on unmount after log cleanup failure
+
+From: Filipe Manana <fdmanana@suse.com>
+
+commit 40cdc509877bacb438213b83c7541c5e24a1d9ec upstream.
+
+After the recent changes made by commit c2e39305299f01 ("btrfs: clear
+extent buffer uptodate when we fail to write it") and its followup fix,
+commit 651740a5024117 ("btrfs: check WRITE_ERR when trying to read an
+extent buffer"), we can now end up not cleaning up space reservations of
+log tree extent buffers after a transaction abort happens, as well as not
+cleaning up still dirty extent buffers.
+
+This happens because if writeback for a log tree extent buffer failed,
+then we have cleared the bit EXTENT_BUFFER_UPTODATE from the extent buffer
+and we have also set the bit EXTENT_BUFFER_WRITE_ERR on it. Later on,
+when trying to free the log tree with free_log_tree(), which iterates
+over the tree, we can end up getting an -EIO error when trying to read
+a node or a leaf, since read_extent_buffer_pages() returns -EIO if an
+extent buffer does not have EXTENT_BUFFER_UPTODATE set and has the
+EXTENT_BUFFER_WRITE_ERR bit set. Getting that -EIO means that we return
+immediately as we can not iterate over the entire tree.
+
+In that case we never update the reserved space for an extent buffer in
+the respective block group and space_info object.
+
+When this happens we get the following traces when unmounting the fs:
+
+[174957.284509] BTRFS: error (device dm-0) in cleanup_transaction:1913: errno=-5 IO failure
+[174957.286497] BTRFS: error (device dm-0) in free_log_tree:3420: errno=-5 IO failure
+[174957.399379] ------------[ cut here ]------------
+[174957.402497] WARNING: CPU: 2 PID: 3206883 at fs/btrfs/block-group.c:127 btrfs_put_block_group+0x77/0xb0 [btrfs]
+[174957.407523] Modules linked in: btrfs overlay dm_zero (...)
+[174957.424917] CPU: 2 PID: 3206883 Comm: umount Tainted: G W 5.16.0-rc5-btrfs-next-109 #1
+[174957.426689] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
+[174957.428716] RIP: 0010:btrfs_put_block_group+0x77/0xb0 [btrfs]
+[174957.429717] Code: 21 48 8b bd (...)
+[174957.432867] RSP: 0018:ffffb70d41cffdd0 EFLAGS: 00010206
+[174957.433632] RAX: 0000000000000001 RBX: ffff8b09c3848000 RCX: ffff8b0758edd1c8
+[174957.434689] RDX: 0000000000000001 RSI: ffffffffc0b467e7 RDI: ffff8b0758edd000
+[174957.436068] RBP: ffff8b0758edd000 R08: 0000000000000000 R09: 0000000000000000
+[174957.437114] R10: 0000000000000246 R11: 0000000000000000 R12: ffff8b09c3848148
+[174957.438140] R13: ffff8b09c3848198 R14: ffff8b0758edd188 R15: dead000000000100
+[174957.439317] FS: 00007f328fb82800(0000) GS:ffff8b0a2d200000(0000) knlGS:0000000000000000
+[174957.440402] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
+[174957.441164] CR2: 00007fff13563e98 CR3: 0000000404f4e005 CR4: 0000000000370ee0
+[174957.442117] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
+[174957.443076] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
+[174957.443948] Call Trace:
+[174957.444264] <TASK>
+[174957.444538] btrfs_free_block_groups+0x255/0x3c0 [btrfs]
+[174957.445238] close_ctree+0x301/0x357 [btrfs]
+[174957.445803] ? call_rcu+0x16c/0x290
+[174957.446250] generic_shutdown_super+0x74/0x120
+[174957.446832] kill_anon_super+0x14/0x30
+[174957.447305] btrfs_kill_super+0x12/0x20 [btrfs]
+[174957.447890] deactivate_locked_super+0x31/0xa0
+[174957.448440] cleanup_mnt+0x147/0x1c0
+[174957.448888] task_work_run+0x5c/0xa0
+[174957.449336] exit_to_user_mode_prepare+0x1e5/0x1f0
+[174957.449934] syscall_exit_to_user_mode+0x16/0x40
+[174957.450512] do_syscall_64+0x48/0xc0
+[174957.450980] entry_SYSCALL_64_after_hwframe+0x44/0xae
+[174957.451605] RIP: 0033:0x7f328fdc4a97
+[174957.452059] Code: 03 0c 00 f7 (...)
+[174957.454320] RSP: 002b:00007fff13564ec8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
+[174957.455262] RAX: 0000000000000000 RBX: 00007f328feea264 RCX: 00007f328fdc4a97
+[174957.456131] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000560b8ae51dd0
+[174957.457118] RBP: 0000560b8ae51ba0 R08: 0000000000000000 R09: 00007fff13563c40
+[174957.458005] R10: 00007f328fe49fc0 R11: 0000000000000246 R12: 0000000000000000
+[174957.459113] R13: 0000560b8ae51dd0 R14: 0000560b8ae51cb0 R15: 0000000000000000
+[174957.460193] </TASK>
+[174957.460534] irq event stamp: 0
+[174957.461003] hardirqs last enabled at (0): [<0000000000000000>] 0x0
+[174957.461947] hardirqs last disabled at (0): [<ffffffffb0e94214>] copy_process+0x934/0x2040
+[174957.463147] softirqs last enabled at (0): [<ffffffffb0e94214>] copy_process+0x934/0x2040
+[174957.465116] softirqs last disabled at (0): [<0000000000000000>] 0x0
+[174957.466323] ---[ end trace bc7ee0c490bce3af ]---
+[174957.467282] ------------[ cut here ]------------
+[174957.468184] WARNING: CPU: 2 PID: 3206883 at fs/btrfs/block-group.c:3976 btrfs_free_block_groups+0x330/0x3c0 [btrfs]
+[174957.470066] Modules linked in: btrfs overlay dm_zero (...)
+[174957.483137] CPU: 2 PID: 3206883 Comm: umount Tainted: G W 5.16.0-rc5-btrfs-next-109 #1
+[174957.484691] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
+[174957.486853] RIP: 0010:btrfs_free_block_groups+0x330/0x3c0 [btrfs]
+[174957.488050] Code: 00 00 00 ad de (...)
+[174957.491479] RSP: 0018:ffffb70d41cffde0 EFLAGS: 00010206
+[174957.492520] RAX: ffff8b08d79310b0 RBX: ffff8b09c3848000 RCX: 0000000000000000
+[174957.493868] RDX: 0000000000000001 RSI: fffff443055ee600 RDI: ffffffffb1131846
+[174957.495183] RBP: ffff8b08d79310b0 R08: 0000000000000000 R09: 0000000000000000
+[174957.496580] R10: 0000000000000001 R11: 0000000000000000 R12: ffff8b08d7931000
+[174957.498027] R13: ffff8b09c38492b0 R14: dead000000000122 R15: dead000000000100
+[174957.499438] FS: 00007f328fb82800(0000) GS:ffff8b0a2d200000(0000) knlGS:0000000000000000
+[174957.500990] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
+[174957.502117] CR2: 00007fff13563e98 CR3: 0000000404f4e005 CR4: 0000000000370ee0
+[174957.503513] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
+[174957.504864] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
+[174957.506167] Call Trace:
+[174957.506654] <TASK>
+[174957.507047] close_ctree+0x301/0x357 [btrfs]
+[174957.507867] ? call_rcu+0x16c/0x290
+[174957.508567] generic_shutdown_super+0x74/0x120
+[174957.509447] kill_anon_super+0x14/0x30
+[174957.510194] btrfs_kill_super+0x12/0x20 [btrfs]
+[174957.511123] deactivate_locked_super+0x31/0xa0
+[174957.511976] cleanup_mnt+0x147/0x1c0
+[174957.512610] task_work_run+0x5c/0xa0
+[174957.513309] exit_to_user_mode_prepare+0x1e5/0x1f0
+[174957.514231] syscall_exit_to_user_mode+0x16/0x40
+[174957.515069] do_syscall_64+0x48/0xc0
+[174957.515718] entry_SYSCALL_64_after_hwframe+0x44/0xae
+[174957.516688] RIP: 0033:0x7f328fdc4a97
+[174957.517413] Code: 03 0c 00 f7 d8 (...)
+[174957.521052] RSP: 002b:00007fff13564ec8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
+[174957.522514] RAX: 0000000000000000 RBX: 00007f328feea264 RCX: 00007f328fdc4a97
+[174957.523950] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000560b8ae51dd0
+[174957.525375] RBP: 0000560b8ae51ba0 R08: 0000000000000000 R09: 00007fff13563c40
+[174957.526763] R10: 00007f328fe49fc0 R11: 0000000000000246 R12: 0000000000000000
+[174957.528058] R13: 0000560b8ae51dd0 R14: 0000560b8ae51cb0 R15: 0000000000000000
+[174957.529404] </TASK>
+[174957.529843] irq event stamp: 0
+[174957.530256] hardirqs last enabled at (0): [<0000000000000000>] 0x0
+[174957.531061] hardirqs last disabled at (0): [<ffffffffb0e94214>] copy_process+0x934/0x2040
+[174957.532075] softirqs last enabled at (0): [<ffffffffb0e94214>] copy_process+0x934/0x2040
+[174957.533083] softirqs last disabled at (0): [<0000000000000000>] 0x0
+[174957.533865] ---[ end trace bc7ee0c490bce3b0 ]---
+[174957.534452] BTRFS info (device dm-0): space_info 4 has 1070841856 free, is not full
+[174957.535404] BTRFS info (device dm-0): space_info total=1073741824, used=2785280, pinned=0, reserved=49152, may_use=0, readonly=65536 zone_unusable=0
+[174957.537029] BTRFS info (device dm-0): global_block_rsv: size 0 reserved 0
+[174957.537859] BTRFS info (device dm-0): trans_block_rsv: size 0 reserved 0
+[174957.538697] BTRFS info (device dm-0): chunk_block_rsv: size 0 reserved 0
+[174957.539552] BTRFS info (device dm-0): delayed_block_rsv: size 0 reserved 0
+[174957.540403] BTRFS info (device dm-0): delayed_refs_rsv: size 0 reserved 0
+
+This also means that in case we have log tree extent buffers that are
+still dirty, we can end up not cleaning them up in case we find an
+extent buffer with EXTENT_BUFFER_WRITE_ERR set on it, as in that case
+we have no way for iterating over the rest of the tree.
+
+This issue is very often triggered with test cases generic/475 and
+generic/648 from fstests.
+
+The issue could almost be fixed by iterating over the io tree attached to
+each log root which keeps tracks of the range of allocated extent buffers,
+log_root->dirty_log_pages, however that does not work and has some
+inconveniences:
+
+1) After we sync the log, we clear the range of the extent buffers from
+ the io tree, so we can't find them after writeback. We could keep the
+ ranges in the io tree, with a separate bit to signal they represent
+ extent buffers already written, but that means we need to hold into
+ more memory until the transaction commits.
+
+ How much more memory is used depends a lot on whether we are able to
+ allocate contiguous extent buffers on disk (and how often) for a log
+ tree - if we are able to, then a single extent state record can
+ represent multiple extent buffers, otherwise we need multiple extent
+ state record structures to track each extent buffer.
+ In fact, my earlier approach did that:
+
+ https://lore.kernel.org/linux-btrfs/3aae7c6728257c7ce2279d6660ee2797e5e34bbd.1641300250.git.fdmanana@suse.com/
+
+ However that can cause a very significant negative impact on
+ performance, not only due to the extra memory usage but also because
+ we get a larger and deeper dirty_log_pages io tree.
+ We got a report that, on beefy machines at least, we can get such
+ performance drop with fsmark for example:
+
+ https://lore.kernel.org/linux-btrfs/20220117082426.GE32491@xsang-OptiPlex-9020/
+
+2) We would be doing it only to deal with an unexpected and exceptional
+ case, which is basically failure to read an extent buffer from disk
+ due to IO failures. On a healthy system we don't expect transaction
+ aborts to happen after all;
+
+3) Instead of relying on iterating the log tree or tracking the ranges
+ of extent buffers in the dirty_log_pages io tree, using the radix
+ tree that tracks extent buffers (fs_info->buffer_radix) to find all
+ log tree extent buffers is not reliable either, because after writeback
+ of an extent buffer it can be evicted from memory by the release page
+ callback of the btree inode (btree_releasepage()).
+
+Since there's no way to be able to properly cleanup a log tree without
+being able to read its extent buffers from disk and without using more
+memory to track the logical ranges of the allocated extent buffers do
+the following:
+
+1) When we fail to cleanup a log tree, setup a flag that indicates that
+ failure;
+
+2) Trigger writeback of all log tree extent buffers that are still dirty,
+ and wait for the writeback to complete. This is just to cleanup their
+ state, page states, page leaks, etc;
+
+3) When unmounting the fs, ignore if the number of bytes reserved in a
+ block group and in a space_info is not 0 if, and only if, we failed to
+ cleanup a log tree. Also ignore only for metadata block groups and the
+ metadata space_info object.
+
+This is far from a perfect solution, but it serves to silence test
+failures such as those from generic/475 and generic/648. However having
+a non-zero value for the reserved bytes counters on unmount after a
+transaction abort, is not such a terrible thing and it's completely
+harmless, it does not affect the filesystem integrity in any way.
+
+Signed-off-by: Filipe Manana <fdmanana@suse.com>
+Signed-off-by: David Sterba <dsterba@suse.com>
+Signed-off-by: Anand Jain <anand.jain@oracle.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ fs/btrfs/block-group.c | 26 ++++++++++++++++++++++++--
+ fs/btrfs/ctree.h | 7 +++++++
+ fs/btrfs/tree-log.c | 23 +++++++++++++++++++++++
+ 3 files changed, 54 insertions(+), 2 deletions(-)
+
+--- a/fs/btrfs/block-group.c
++++ b/fs/btrfs/block-group.c
+@@ -124,7 +124,16 @@ void btrfs_put_block_group(struct btrfs_
+ {
+ if (refcount_dec_and_test(&cache->refs)) {
+ WARN_ON(cache->pinned > 0);
+- WARN_ON(cache->reserved > 0);
++ /*
++ * If there was a failure to cleanup a log tree, very likely due
++ * to an IO failure on a writeback attempt of one or more of its
++ * extent buffers, we could not do proper (and cheap) unaccounting
++ * of their reserved space, so don't warn on reserved > 0 in that
++ * case.
++ */
++ if (!(cache->flags & BTRFS_BLOCK_GROUP_METADATA) ||
++ !BTRFS_FS_LOG_CLEANUP_ERROR(cache->fs_info))
++ WARN_ON(cache->reserved > 0);
+
+ /*
+ * A block_group shouldn't be on the discard_list anymore.
+@@ -3987,9 +3996,22 @@ int btrfs_free_block_groups(struct btrfs
+ * important and indicates a real bug if this happens.
+ */
+ if (WARN_ON(space_info->bytes_pinned > 0 ||
+- space_info->bytes_reserved > 0 ||
+ space_info->bytes_may_use > 0))
+ btrfs_dump_space_info(info, space_info, 0, 0);
++
++ /*
++ * If there was a failure to cleanup a log tree, very likely due
++ * to an IO failure on a writeback attempt of one or more of its
++ * extent buffers, we could not do proper (and cheap) unaccounting
++ * of their reserved space, so don't warn on bytes_reserved > 0 in
++ * that case.
++ */
++ if (!(space_info->flags & BTRFS_BLOCK_GROUP_METADATA) ||
++ !BTRFS_FS_LOG_CLEANUP_ERROR(info)) {
++ if (WARN_ON(space_info->bytes_reserved > 0))
++ btrfs_dump_space_info(info, space_info, 0, 0);
++ }
++
+ WARN_ON(space_info->reclaim_size > 0);
+ list_del(&space_info->list);
+ btrfs_sysfs_remove_space_info(space_info);
+--- a/fs/btrfs/ctree.h
++++ b/fs/btrfs/ctree.h
+@@ -143,6 +143,9 @@ enum {
+ BTRFS_FS_STATE_DEV_REPLACING,
+ /* The btrfs_fs_info created for self-tests */
+ BTRFS_FS_STATE_DUMMY_FS_INFO,
++
++ /* Indicates there was an error cleaning up a log tree. */
++ BTRFS_FS_STATE_LOG_CLEANUP_ERROR,
+ };
+
+ #define BTRFS_BACKREF_REV_MAX 256
+@@ -3585,6 +3588,10 @@ static inline void btrfs_print_v0_err(st
+ "Unsupported V0 extent filesystem detected. Aborting. Please re-create your filesystem with a newer kernel");
+ }
+
++#define BTRFS_FS_LOG_CLEANUP_ERROR(fs_info) \
++ (unlikely(test_bit(BTRFS_FS_STATE_LOG_CLEANUP_ERROR, \
++ &(fs_info)->fs_state)))
++
+ __printf(5, 6)
+ __cold
+ void __btrfs_handle_fs_error(struct btrfs_fs_info *fs_info, const char *function,
+--- a/fs/btrfs/tree-log.c
++++ b/fs/btrfs/tree-log.c
+@@ -3449,6 +3449,29 @@ static void free_log_tree(struct btrfs_t
+ if (log->node) {
+ ret = walk_log_tree(trans, log, &wc);
+ if (ret) {
++ /*
++ * We weren't able to traverse the entire log tree, the
++ * typical scenario is getting an -EIO when reading an
++ * extent buffer of the tree, due to a previous writeback
++ * failure of it.
++ */
++ set_bit(BTRFS_FS_STATE_LOG_CLEANUP_ERROR,
++ &log->fs_info->fs_state);
++
++ /*
++ * Some extent buffers of the log tree may still be dirty
++ * and not yet written back to storage, because we may
++ * have updates to a log tree without syncing a log tree,
++ * such as during rename and link operations. So flush
++ * them out and wait for their writeback to complete, so
++ * that we properly cleanup their state and pages.
++ */
++ btrfs_write_marked_extents(log->fs_info,
++ &log->dirty_log_pages,
++ EXTENT_DIRTY | EXTENT_NEW);
++ btrfs_wait_tree_log_extents(log,
++ EXTENT_DIRTY | EXTENT_NEW);
++
+ if (trans)
+ btrfs_abort_transaction(trans, ret);
+ else
projects / thirdparty / kernel / stable-queue.git / commitdiff
