[PATCH RFC v4 2/3] iomap: use BIO_COMPLETE_IN_TASK for dropbehind writeback

[Tal Zussman <tz2294@columbia.edu>]

Set BIO_COMPLETE_IN_TASK on iomap writeback bios when
IOMAP_IOEND_DONTCACHE is set. This ensures that bi_end_io runs in task
context, where folio_end_dropbehind() can safely invalidate folios.

With the bio layer now handling task-context deferral generically, XFS
no longer needs to route DONTCACHE ioends through its completion
workqueue for page cache invalidation. Remove the DONTCACHE check from
xfs_ioend_needs_wq_completion().

Signed-off-by: Tal Zussman <tz2294@columbia.edu>
---
 fs/iomap/ioend.c  | 2 ++
 fs/xfs/xfs_aops.c | 4 ----
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/fs/iomap/ioend.c b/fs/iomap/ioend.c
index e4d57cb969f1..6b8375d11cc0 100644
--- a/fs/iomap/ioend.c
+++ b/fs/iomap/ioend.c
@@ -113,6 +113,8 @@ static struct iomap_ioend *iomap_alloc_ioend(struct iomap_writepage_ctx *wpc,
 			       GFP_NOFS, &iomap_ioend_bioset);
 	bio->bi_iter.bi_sector = iomap_sector(&wpc->iomap, pos);
 	bio->bi_write_hint = wpc->inode->i_write_hint;
+	if (ioend_flags & IOMAP_IOEND_DONTCACHE)
+		bio_set_flag(bio, BIO_COMPLETE_IN_TASK);
 	wbc_init_bio(wpc->wbc, bio);
 	wpc->nr_folios = 0;
 	return iomap_init_ioend(wpc->inode, bio, pos, ioend_flags);
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 76678814f46f..0d469b91377d 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -510,10 +510,6 @@ xfs_ioend_needs_wq_completion(
 	if (ioend->io_flags & (IOMAP_IOEND_UNWRITTEN | IOMAP_IOEND_SHARED))
 		return true;
 
-	/* Page cache invalidation cannot be done in irq context. */
-	if (ioend->io_flags & IOMAP_IOEND_DONTCACHE)
-		return true;
-
 	return false;
 }
 

-- 
2.39.5