From 95848dcb9d676738411a8ff70a9704039f1b3982 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Sat, 5 Aug 2023 07:55:37 +0200 Subject: [PATCH] zram: take device and not only bvec offset into account Commit af8b04c63708 ("zram: simplify bvec iteration in __zram_make_request") changed the bio iteration in zram to rely on the implicit capping to page boundaries in bio_for_each_segment. But it failed to care for the fact zram not only care about the page alignment of the bio payload, but also the page alignment into the device. For buffered I/O and swap those are the same, but for direct I/O or kernel internal I/O like XFS log buffer writes they can differ. Fix this by open coding bio_for_each_segment and limiting the bvec len so that it never crosses over a page alignment boundary in the device in addition to the payload boundary already taken care of by bio_iter_iovec. Cc: stable@vger.kernel.org Fixes: af8b04c63708 ("zram: simplify bvec iteration in __zram_make_request") Reported-by: Dusty Mabe Signed-off-by: Christoph Hellwig Acked-by: Sergey Senozhatsky Link: https://lore.kernel.org/r/20230805055537.147835-1-hch@lst.de Signed-off-by: Jens Axboe --- drivers/block/zram/zram_drv.c | 32 ++++++++++++++++++++------------ 1 file changed, 20 insertions(+), 12 deletions(-) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 5676e6d..06673c6 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -1870,15 +1870,16 @@ static void zram_bio_discard(struct zram *zram, struct bio *bio) static void zram_bio_read(struct zram *zram, struct bio *bio) { - struct bvec_iter iter; - struct bio_vec bv; - unsigned long start_time; + unsigned long start_time = bio_start_io_acct(bio); + struct bvec_iter iter = bio->bi_iter; - start_time = bio_start_io_acct(bio); - bio_for_each_segment(bv, bio, iter) { + do { u32 index = iter.bi_sector >> SECTORS_PER_PAGE_SHIFT; u32 offset = (iter.bi_sector & (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT; + struct bio_vec bv = bio_iter_iovec(bio, iter); + + bv.bv_len = min_t(u32, bv.bv_len, PAGE_SIZE - offset); if (zram_bvec_read(zram, &bv, index, offset, bio) < 0) { atomic64_inc(&zram->stats.failed_reads); @@ -1890,22 +1891,26 @@ static void zram_bio_read(struct zram *zram, struct bio *bio) zram_slot_lock(zram, index); zram_accessed(zram, index); zram_slot_unlock(zram, index); - } + + bio_advance_iter_single(bio, &iter, bv.bv_len); + } while (iter.bi_size); + bio_end_io_acct(bio, start_time); bio_endio(bio); } static void zram_bio_write(struct zram *zram, struct bio *bio) { - struct bvec_iter iter; - struct bio_vec bv; - unsigned long start_time; + unsigned long start_time = bio_start_io_acct(bio); + struct bvec_iter iter = bio->bi_iter; - start_time = bio_start_io_acct(bio); - bio_for_each_segment(bv, bio, iter) { + do { u32 index = iter.bi_sector >> SECTORS_PER_PAGE_SHIFT; u32 offset = (iter.bi_sector & (SECTORS_PER_PAGE - 1)) << SECTOR_SHIFT; + struct bio_vec bv = bio_iter_iovec(bio, iter); + + bv.bv_len = min_t(u32, bv.bv_len, PAGE_SIZE - offset); if (zram_bvec_write(zram, &bv, index, offset, bio) < 0) { atomic64_inc(&zram->stats.failed_writes); @@ -1916,7 +1921,10 @@ static void zram_bio_write(struct zram *zram, struct bio *bio) zram_slot_lock(zram, index); zram_accessed(zram, index); zram_slot_unlock(zram, index); - } + + bio_advance_iter_single(bio, &iter, bv.bv_len); + } while (iter.bi_size); + bio_end_io_acct(bio, start_time); bio_endio(bio); } -- 2.7.4