If there are pending blocks to be released after a commit, retrying
the allocation after a journal commit has no hope of helping.  So
track how many pending deleted blocks there might be, and don't retry
if there are no pending blocks.

Reported-by: Chao Yu <redacted>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---

Oops, ignore the earlier version of this patch.  I bobbled the commit
and merged in part of another change.

fs/ext4/balloc.c    |  9 ++++++++-
fs/ext4/ext4.h      |  1 +
fs/ext4/ext4_jbd2.h | 10 +++++++++-
fs/ext4/mballoc.c   | 12 ++++++++++--
4 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 3020fd7..371ac63 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c

@@ -603,7 +603,14 @@ int ext4_claim_free_clusters(struct ext4_sb_info *sbi,
 */

int ext4_should_retry_alloc(struct super_block *sb, int *retries)
{
-	if (!ext4_has_free_clusters(EXT4_SB(sb), 1, 0) ||
+	unsigned int pending_blocks;
+
+	spin_lock(&EXT4_SB(sb)->s_md_lock);
+	pending_blocks = EXT4_SB(sb)->s_mb_free_pending;
+	spin_unlock(&EXT4_SB(sb)->s_md_lock);

+
+	if (pending_blocks == 0 ||
+	    !ext4_has_free_clusters(EXT4_SB(sb), 1, 0) ||
	    (*retries)++ > 3 ||
	    !EXT4_SB(sb)->s_journal)
		return 0;

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index b84aa1c..96c73e6 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h

@@ -1430,6 +1430,7 @@ struct ext4_sb_info {

	unsigned short *s_mb_offsets;
	unsigned int *s_mb_maxs;
	unsigned int s_group_info_size;
+	unsigned int s_mb_free_pending;

	/* tunables */
	unsigned long s_stripe;

diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h
index 09c1ef3..b1d52c1 100644
--- a/fs/ext4/ext4_jbd2.h
+++ b/fs/ext4/ext4_jbd2.h

@@ -175,6 +175,13 @@ struct ext4_journal_cb_entry {
 * There is no guaranteed calling order of multiple registered callbacks on
 * the same transaction.
 */
+static inline void _ext4_journal_callback_add(handle_t *handle,
+			struct ext4_journal_cb_entry *jce)
+{
+	/* Add the jce to transaction's private list */
+	list_add_tail(&jce->jce_list, &handle->h_transaction->t_private_list);
+}
+

static inline void ext4_journal_callback_add(handle_t *handle,
			void (*func)(struct super_block *sb,
				     struct ext4_journal_cb_entry *jce,

@@ -187,10 +194,11 @@ static inline void ext4_journal_callback_add(handle_t *handle,

	/* Add the jce to transaction's private list */
	jce->jce_func = func;
	spin_lock(&sbi->s_md_lock);
-	list_add_tail(&jce->jce_list, &handle->h_transaction->t_private_list);
+	_ext4_journal_callback_add(handle, jce);
	spin_unlock(&sbi->s_md_lock);
}

+
/**
 * ext4_journal_callback_del: delete a registered callback
 * @handle: active journal transaction handle on which callback was registered

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index c1ab3ec..77249e1 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c

@@ -2627,6 +2627,7 @@ int ext4_mb_init(struct super_block *sb)

	spin_lock_init(&sbi->s_md_lock);
	spin_lock_init(&sbi->s_bal_lock);
+	sbi->s_mb_free_pending = 0;

	sbi->s_mb_max_to_scan = MB_DEFAULT_MAX_TO_SCAN;
	sbi->s_mb_min_to_scan = MB_DEFAULT_MIN_TO_SCAN;

@@ -2814,6 +2815,9 @@ static void ext4_free_data_callback(struct super_block *sb,

	/* we expect to find existing buddy because it's pinned */
	BUG_ON(err != 0);

+	spin_lock(&EXT4_SB(sb)->s_md_lock);
+	EXT4_SB(sb)->s_mb_free_pending -= entry->efd_count;
+	spin_unlock(&EXT4_SB(sb)->s_md_lock);

	db = e4b.bd_info;
	/* there are blocks to put in buddy to make them really free */

@@ -4583,6 +4587,7 @@ ext4_mb_free_metadata(handle_t *handle, struct ext4_buddy *e4b,

{
	ext4_group_t group = e4b->bd_group;
	ext4_grpblk_t cluster;
+	ext4_grpblk_t clusters = new_entry->efd_count;
	struct ext4_free_data *entry;
	struct ext4_group_info *db = e4b->bd_info;
	struct super_block *sb = e4b->bd_sb;

@@ -4649,8 +4654,11 @@ ext4_mb_free_metadata(handle_t *handle, struct ext4_buddy *e4b,

		}
	}
	/* Add the extent to transaction's private list */
-	ext4_journal_callback_add(handle, ext4_free_data_callback,
-				  &new_entry->efd_jce);
+	new_entry->efd_jce.jce_func = ext4_free_data_callback;
+	spin_lock(&sbi->s_md_lock);
+	_ext4_journal_callback_add(handle, &new_entry->efd_jce);
+	sbi->s_mb_free_pending += clusters;
+	spin_unlock(&sbi->s_md_lock);
	return 0;
}

--
2.5.0

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