[PATCH 1/2] xfs: add a separate bio_set for spliting GC writes

[Christoph Hellwig <hch@lst.de>]

Allocating the new bio for a split from the same pool as the original
one can deadlock under memory pressure as the origin bio could be the
last one from the mempool.

Add a separate pool for splitting GC write bios to avoid this.

Fixes: 080d01c41d44 ("xfs: implement zoned garbage collection")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
---
 fs/xfs/xfs_zone_gc.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_zone_gc.c b/fs/xfs/xfs_zone_gc.c
index f76a09130852..e4f70e024632 100644
--- a/fs/xfs/xfs_zone_gc.c
+++ b/fs/xfs/xfs_zone_gc.c
@@ -130,6 +130,9 @@ struct xfs_zone_gc_data {
 	/* bioset used to allocate the gc_bios */
 	struct bio_set			bio_set;
 
+	/* bioset used when writes need to be split to hardware limits */
+	struct bio_set			split_bio_set;
+
 	/*
 	 * Scratchpad to buffer GC data, organized as a ring buffer over
 	 * discontiguous folios.  scratch_head is where the buffer is filled,
@@ -221,6 +224,9 @@ xfs_zone_gc_data_alloc(
 	if (bioset_init(&data->bio_set, 16, offsetof(struct xfs_gc_bio, bio),
 			BIOSET_NEED_BVECS))
 		goto out_free_recs;
+	if (bioset_init(&data->split_bio_set, 16,
+			offsetof(struct xfs_gc_bio, bio), 0))
+		goto out_exit_bio_set;
 	for (i = 0; i < XFS_GC_NR_BUFS; i++) {
 		data->scratch_folios[i] =
 			folio_alloc(GFP_KERNEL, get_order(XFS_GC_BUF_SIZE));
@@ -238,6 +244,8 @@ xfs_zone_gc_data_alloc(
 out_free_scratch:
 	while (--i >= 0)
 		folio_put(data->scratch_folios[i]);
+	bioset_exit(&data->split_bio_set);
+out_exit_bio_set:
 	bioset_exit(&data->bio_set);
 out_free_recs:
 	kfree(data->iter.recs);
@@ -254,6 +262,7 @@ xfs_zone_gc_data_free(
 
 	for (i = 0; i < XFS_GC_NR_BUFS; i++)
 		folio_put(data->scratch_folios[i]);
+	bioset_exit(&data->split_bio_set);
 	bioset_exit(&data->bio_set);
 	kfree(data->iter.recs);
 	kfree(data);
@@ -810,7 +819,8 @@ xfs_zone_gc_split_write(
 			data->mp->m_sb.sb_blocksize) >> SECTOR_SHIFT;
 	split_len = split_sectors << SECTOR_SHIFT;
 
-	split = bio_split(&chunk->bio, split_sectors, GFP_NOFS, &data->bio_set);
+	split = bio_split(&chunk->bio, split_sectors, GFP_NOFS,
+			&data->split_bio_set);
 	split_chunk = container_of(split, struct xfs_gc_bio, bio);
 	split_chunk->data = data;
 	ihold(VFS_I(chunk->ip));
-- 
2.53.0