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charset="utf-8" ---------- Forwarded message --------- =E5=8F=91=E4=BB=B6=E4=BA=BA=EF=BC=9A zhangshida Date: 2026=E5=B9=B41=E6=9C=8820=E6=97=A5=E5=91=A8=E4=BA=8C 10:35 Subject: [PATCH v2] bcache: use bio cloning for detached device requests To: , , , , Cc: , , , , Christoph Hellwig From: Shida Zhang Previously, bcache hijacked the bi_end_io and bi_private fields of the incoming bio when the backing device was in a detached state. This is fragile and breaks if the bio is needed to be processed by other layers. This patch transitions to using a cloned bio embedded within a private structure. This ensures the original bio's metadata remains untouched. Fixes: 53280e398471 ("bcache: fix improper use of bi_end_io") Co-developed-by: Christoph Hellwig Signed-off-by: Christoph Hellwig Signed-off-by: Shida Zhang --- Changelog: v1: https://lore.kernel.org/all/20260115074811.230807-1-zhangshida@kylinos.cn/ drivers/md/bcache/bcache.h | 9 +++++ drivers/md/bcache/request.c | 79 ++++++++++++++++--------------------- drivers/md/bcache/super.c | 12 +++++- 3 files changed, 54 insertions(+), 46 deletions(-) diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h index 8ccacba8554..54ff4e0238a 100644 --- a/drivers/md/bcache/bcache.h +++ b/drivers/md/bcache/bcache.h @@ -273,6 +273,8 @@ struct bcache_device { struct bio_set bio_split; + struct bio_set bio_detach; + unsigned int data_csum:1; int (*cache_miss)(struct btree *b, struct search *s, @@ -753,6 +755,13 @@ struct bbio { struct bio bio; }; +struct detached_dev_io_private { + struct bcache_device *d; + unsigned long start_time; + struct bio *orig_bio; + struct bio bio; +}; + #define BTREE_PRIO USHRT_MAX #define INITIAL_PRIO 32768U diff --git a/drivers/md/bcache/request.c b/drivers/md/bcache/request.c index 82fdea7dea7..e0b12cb622b 100644 --- a/drivers/md/bcache/request.c +++ b/drivers/md/bcache/request.c @@ -1077,68 +1077,58 @@ static CLOSURE_CALLBACK(cached_dev_nodata) continue_at(cl, cached_dev_bio_complete, NULL); } -struct detached_dev_io_private { - struct bcache_device *d; - unsigned long start_time; - bio_end_io_t *bi_end_io; - void *bi_private; - struct block_device *orig_bdev; -}; - static void detached_dev_end_io(struct bio *bio) { - struct detached_dev_io_private *ddip; - - ddip =3D bio->bi_private; - bio->bi_end_io =3D ddip->bi_end_io; - bio->bi_private =3D ddip->bi_private; + struct detached_dev_io_private *ddip =3D + container_of(bio, struct detached_dev_io_private, bio); + struct bio *orig_bio =3D ddip->orig_bio; /* Count on the bcache device */ - bio_end_io_acct_remapped(bio, ddip->start_time, ddip->orig_bdev); + bio_end_io_acct(orig_bio, ddip->start_time); if (bio->bi_status) { - struct cached_dev *dc =3D container_of(ddip->d, - struct cached_dev, dis= k); + struct cached_dev *dc =3D bio->bi_private; + /* should count I/O error for backing device here */ bch_count_backing_io_errors(dc, bio); + orig_bio->bi_status =3D bio->bi_status; } - kfree(ddip); - bio_endio(bio); + bio_put(bio); + bio_endio(orig_bio); } -static void detached_dev_do_request(struct bcache_device *d, struct bio *b= io, - struct block_device *orig_bdev, unsigned long start_time) +static void detached_dev_do_request(struct bcache_device *d, + struct bio *orig_bio, unsigned long start_time) { struct detached_dev_io_private *ddip; struct cached_dev *dc =3D container_of(d, struct cached_dev, disk); + struct bio *clone_bio; - /* - * no need to call closure_get(&dc->disk.cl), - * because upper layer had already opened bcache device, - * which would call closure_get(&dc->disk.cl) - */ - ddip =3D kzalloc(sizeof(struct detached_dev_io_private), GFP_NOIO); - if (!ddip) { - bio->bi_status =3D BLK_STS_RESOURCE; - bio_endio(bio); + if (bio_op(orig_bio) =3D=3D REQ_OP_DISCARD && + !bdev_max_discard_sectors(dc->bdev)) { + bio_endio(orig_bio); return; } - ddip->d =3D d; + clone_bio =3D bio_alloc_clone(dc->bdev, orig_bio, GFP_NOIO, + &d->bio_detach); + if (!clone_bio) { + orig_bio->bi_status =3D BLK_STS_RESOURCE; + bio_endio(orig_bio); + return; + } + + ddip =3D container_of(clone_bio, struct detached_dev_io_private, bi= o); /* Count on the bcache device */ - ddip->orig_bdev =3D orig_bdev; + ddip->d =3D d; ddip->start_time =3D start_time; - ddip->bi_end_io =3D bio->bi_end_io; - ddip->bi_private =3D bio->bi_private; - bio->bi_end_io =3D detached_dev_end_io; - bio->bi_private =3D ddip; - - if ((bio_op(bio) =3D=3D REQ_OP_DISCARD) && - !bdev_max_discard_sectors(dc->bdev)) - detached_dev_end_io(bio); - else - submit_bio_noacct(bio); + ddip->orig_bio =3D orig_bio; + + clone_bio->bi_end_io =3D detached_dev_end_io; + clone_bio->bi_private =3D dc; + + submit_bio_noacct(clone_bio); } static void quit_max_writeback_rate(struct cache_set *c, @@ -1214,10 +1204,10 @@ void cached_dev_submit_bio(struct bio *bio) start_time =3D bio_start_io_acct(bio); - bio_set_dev(bio, dc->bdev); bio->bi_iter.bi_sector +=3D dc->sb.data_offset; if (cached_dev_get(dc)) { + bio_set_dev(bio, dc->bdev); s =3D search_alloc(bio, d, orig_bdev, start_time); trace_bcache_request_start(s->d, bio); @@ -1237,9 +1227,10 @@ void cached_dev_submit_bio(struct bio *bio) else cached_dev_read(dc, s); } - } else + } else { /* I/O request sent to backing device */ - detached_dev_do_request(d, bio, orig_bdev, start_time); + detached_dev_do_request(d, bio, start_time); + } } static int cached_dev_ioctl(struct bcache_device *d, blk_mode_t mode, diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index c17d4517af2..d4b798668c8 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -887,6 +887,7 @@ static void bcache_device_free(struct bcache_device *d) } bioset_exit(&d->bio_split); + bioset_exit(&d->bio_detach); kvfree(d->full_dirty_stripes); kvfree(d->stripe_sectors_dirty); @@ -949,6 +950,11 @@ static int bcache_device_init(struct bcache_device *d, unsigned int block_size, BIOSET_NEED_BVECS|BIOSET_NEED_RESCUER)) goto out_ida_remove; + if (bioset_init(&d->bio_detach, 4, + offsetof(struct detached_dev_io_private, bio), + BIOSET_NEED_BVECS|BIOSET_NEED_RESCUER)) + goto out_bioset_split_exit; + if (lim.logical_block_size > PAGE_SIZE && cached_bdev) { /* * This should only happen with BCACHE_SB_VERSION_BDEV. @@ -964,7 +970,7 @@ static int bcache_device_init(struct bcache_device *d, unsigned int block_size, d->disk =3D blk_alloc_disk(&lim, NUMA_NO_NODE); if (IS_ERR(d->disk)) - goto out_bioset_exit; + goto out_bioset_detach_exit; set_capacity(d->disk, sectors); snprintf(d->disk->disk_name, DISK_NAME_LEN, "bcache%i", idx); @@ -976,7 +982,9 @@ static int bcache_device_init(struct bcache_device *d, unsigned int block_size, d->disk->private_data =3D d; return 0; -out_bioset_exit: +out_bioset_detach_exit: + bioset_exit(&d->bio_detach); +out_bioset_split_exit: bioset_exit(&d->bio_split); out_ida_remove: ida_free(&bcache_device_idx, idx); -- 2.34.1