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iomap: use BIO_COMPLETE_IN_TASK for dropbehind writeback

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Set BIO_COMPLETE_IN_TASK on iomap writeback bios when a dropbehind folio
is added. 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,
IOMAP_IOEND_DONTCACHE is no longer needed, as XFS no longer needs to
route DONTCACHE ioends through its completion workqueue. Remove the flag
and its NOMERGE entry.

Without the NOMERGE, regular I/Os that get merged with a dropbehind
folio will also have their completion deferred to task context.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Tal Zussman <tz2294@columbia.edu>
Link: https://patch.msgid.link/20260730-blk-dontcache-v7-3-3e8e6850068d@columbia.edu
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Tal Zussman
2026-07-30 02:57:53 -04:00
committed by Jens Axboe
parent 77e73fa61b
commit efbde6f9f4
3 changed files with 4 additions and 10 deletions
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5
fs/iomap/ioend.c
View File

@@ -238,8 +238,6 @@ ssize_t iomap_add_to_ioend(struct iomap_writepage_ctx *wpc, struct folio *folio,
if (wpc->iomap.flags & IOMAP_F_SHARED)
ioend_flags |= IOMAP_IOEND_SHARED;
if (folio_test_dropbehind(folio))
ioend_flags |= IOMAP_IOEND_DONTCACHE;
if (pos == wpc->iomap.offset && (wpc->iomap.flags & IOMAP_F_BOUNDARY))
ioend_flags |= IOMAP_IOEND_BOUNDARY;
@@ -256,6 +254,9 @@ ssize_t iomap_add_to_ioend(struct iomap_writepage_ctx *wpc, struct folio *folio,
if (!bio_add_folio(&ioend->io_bio, folio, map_len, poff))
goto new_ioend;
if (folio_test_dropbehind(folio))
bio_set_flag(&ioend->io_bio, BIO_COMPLETE_IN_TASK);
/*
* Clamp io_offset and io_size to the incore EOF so that ondisk
* file size updates in the ioend completion are byte-accurate.

4
fs/xfs/xfs_aops.c
View File

@@ -522,10 +522,6 @@ 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;
}

5
include/linux/iomap.h
View File

@@ -404,16 +404,13 @@ sector_t iomap_bmap(struct address_space *mapping, sector_t bno,
#define IOMAP_IOEND_BOUNDARY (1U << 2)
/* is direct I/O */
#define IOMAP_IOEND_DIRECT (1U << 3)
/* is DONTCACHE I/O */
#define IOMAP_IOEND_DONTCACHE (1U << 4)
/*
* Flags that if set on either ioend prevent the merge of two ioends.
* (IOMAP_IOEND_BOUNDARY also prevents merges, but only one-way)
*/
#define IOMAP_IOEND_NOMERGE_FLAGS \
(IOMAP_IOEND_SHARED | IOMAP_IOEND_UNWRITTEN | IOMAP_IOEND_DIRECT | \
IOMAP_IOEND_DONTCACHE)
(IOMAP_IOEND_SHARED | IOMAP_IOEND_UNWRITTEN | IOMAP_IOEND_DIRECT)
/*
* Structure for writeback I/O completions.