Commit 1e1c50a9 authored by Nikolay Borisov's avatar Nikolay Borisov Committed by David Sterba

btrfs: Fix possible softlock on single core machines

do_chunk_alloc implements a loop checking whether there is a pending
chunk allocation and if so causes the caller do loop. Generally this
loop is executed only once, however testing with btrfs/072 on a single
core vm machines uncovered an extreme case where the system could loop
indefinitely. This is due to a missing cond_resched when loop which
doesn't give a chance to the previous chunk allocator finish its job.

The fix is to simply add the missing cond_resched.

Fixes: 6d74119f ("Btrfs: avoid taking the chunk_mutex in do_chunk_alloc")
Signed-off-by: default avatarNikolay Borisov <nborisov@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent b98def7c
...@@ -4643,6 +4643,7 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans, ...@@ -4643,6 +4643,7 @@ static int do_chunk_alloc(struct btrfs_trans_handle *trans,
if (wait_for_alloc) { if (wait_for_alloc) {
mutex_unlock(&fs_info->chunk_mutex); mutex_unlock(&fs_info->chunk_mutex);
wait_for_alloc = 0; wait_for_alloc = 0;
cond_resched();
goto again; goto again;
} }
......
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