diff mbox series

[v2,2/5] btrfs: splice remaining dirty_bg's onto the transaction dirty bg list

Message ID b7495cd02ea95c2d4a0859beec708723c018586e.1610650736.git.josef@toxicpanda.com (mailing list archive)
State New, archived
Headers show
Series Serious fixes for different error paths | expand

Commit Message

Josef Bacik Jan. 14, 2021, 7:02 p.m. UTC
While doing error injection testing with my relocation patches I hit the
following ASSERT()

assertion failed: list_empty(&block_group->dirty_list), in fs/btrfs/block-group.c:3356
------------[ cut here ]------------
kernel BUG at fs/btrfs/ctree.h:3357!
invalid opcode: 0000 [#1] SMP NOPTI
CPU: 0 PID: 24351 Comm: umount Tainted: G        W         5.10.0-rc3+ #193
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.13.0-2.fc32 04/01/2014
RIP: 0010:assertfail.constprop.0+0x18/0x1a
RSP: 0018:ffffa09b019c7e00 EFLAGS: 00010282
RAX: 0000000000000056 RBX: ffff8f6492c18000 RCX: 0000000000000000
RDX: ffff8f64fbc27c60 RSI: ffff8f64fbc19050 RDI: ffff8f64fbc19050
RBP: ffff8f6483bbdc00 R08: 0000000000000000 R09: 0000000000000000
R10: ffffa09b019c7c38 R11: ffffffff85d70928 R12: ffff8f6492c18100
R13: ffff8f6492c18148 R14: ffff8f6483bbdd70 R15: dead000000000100
FS:  00007fbfda4cdc40(0000) GS:ffff8f64fbc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fbfda666fd0 CR3: 000000013cf66002 CR4: 0000000000370ef0
Call Trace:
 ? fsnotify_destroy_marks+0x14/0x100

This happened because I injected an error in btrfs_cow_block() while
running the dirty block groups.  When we run the dirty block groups, we
splice the list onto a local list to process.  However if an error
occurs, we only cleanup the transactions dirty block group list, not any
pending block groups we have on our locally spliced list.

In fact if we fail to allocate a path in this function we'll also fail
to clean up the splice list.

Fix this by splicing the list back onto the transaction dirty block
group list so that the block groups are cleaned up.  Then add a 'out'
label and have the error conditions jump to out so that the errors are
handled properly.  This also has the side-effect of fixing a problem
where we would clear 'ret' on error because we unconditionally ran

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
 fs/btrfs/block-group.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)
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diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 0886e81e5540..73632782d0cd 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -2556,8 +2556,10 @@  int btrfs_start_dirty_block_groups(struct btrfs_trans_handle *trans)
 	if (!path) {
 		path = btrfs_alloc_path();
-		if (!path)
-			return -ENOMEM;
+		if (!path) {
+			ret = -ENOMEM;
+			goto out;
+		}
@@ -2651,16 +2653,14 @@  int btrfs_start_dirty_block_groups(struct btrfs_trans_handle *trans)
 		if (drop_reserve)
 			btrfs_delayed_refs_rsv_release(fs_info, 1);
-		if (ret)
-			break;
 		 * Avoid blocking other tasks for too long. It might even save
 		 * us from writing caches for block groups that are going to be
 		 * removed.
+		if (ret)
+			goto out;
@@ -2684,7 +2684,12 @@  int btrfs_start_dirty_block_groups(struct btrfs_trans_handle *trans)
 			goto again;
-	} else if (ret < 0) {
+	}
+	if (ret < 0) {
+		spin_lock(&cur_trans->dirty_bgs_lock);
+		list_splice_init(&dirty, &cur_trans->dirty_bgs);
+		spin_unlock(&cur_trans->dirty_bgs_lock);
 		btrfs_cleanup_dirty_bgs(cur_trans, fs_info);