summaryrefslogtreecommitdiff
path: root/fs/btrfs/transaction.c
diff options
context:
space:
mode:
Diffstat (limited to 'fs/btrfs/transaction.c')
-rw-r--r--fs/btrfs/transaction.c12
1 files changed, 10 insertions, 2 deletions
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index c43bbc7f623e..c3cfdfd8de9b 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1981,16 +1981,24 @@ static void btrfs_cleanup_pending_block_groups(struct btrfs_trans_handle *trans)
static inline int btrfs_start_delalloc_flush(struct btrfs_fs_info *fs_info)
{
/*
- * We use writeback_inodes_sb here because if we used
+ * We use try_to_writeback_inodes_sb() here because if we used
* btrfs_start_delalloc_roots we would deadlock with fs freeze.
* Currently are holding the fs freeze lock, if we do an async flush
* we'll do btrfs_join_transaction() and deadlock because we need to
* wait for the fs freeze lock. Using the direct flushing we benefit
* from already being in a transaction and our join_transaction doesn't
* have to re-take the fs freeze lock.
+ *
+ * Note that try_to_writeback_inodes_sb() will only trigger writeback
+ * if it can read lock sb->s_umount. It will always be able to lock it,
+ * except when the filesystem is being unmounted or being frozen, but in
+ * those cases sync_filesystem() is called, which results in calling
+ * writeback_inodes_sb() while holding a write lock on sb->s_umount.
+ * Note that we don't call writeback_inodes_sb() directly, because it
+ * will emit a warning if sb->s_umount is not locked.
*/
if (btrfs_test_opt(fs_info, FLUSHONCOMMIT))
- writeback_inodes_sb(fs_info->sb, WB_REASON_SYNC);
+ try_to_writeback_inodes_sb(fs_info->sb, WB_REASON_SYNC);
return 0;
}