bio_alloc can allocate a bio with at most BIO_MAX_PAGES (256) vector entries. However, the incoming bio may have more vector entries if it was allocated by other means. For example, bcache submits bios with more than BIO_MAX_PAGES entries. This results in bio_alloc failure.
To avoid the failure, change the code so that it allocates bio with at most BIO_MAX_PAGES entries. If the incoming bio has more entries, bio_add_page will fail and a new bio will be allocated - the code that handles bio_add_page failure already exists in the dm-log-writes target. Also, move atomic_inc(&lc->io_blocks) before bio_alloc to fix a bug that the target hangs if bio_alloc fails. The error path does put_io_block(lc), so we must do atomic_inc(&lc->io_blocks) before invoking the error path to avoid underflow of lc->io_blocks. Signed-off-by: Mikulas Patocka <[email protected]> Cc: [email protected] # v4.1+ Index: linux-4.6/drivers/md/dm-log-writes.c =================================================================== --- linux-4.6.orig/drivers/md/dm-log-writes.c +++ linux-4.6/drivers/md/dm-log-writes.c @@ -258,12 +258,12 @@ static int log_one_block(struct log_writ goto out; sector++; - bio = bio_alloc(GFP_KERNEL, block->vec_cnt); + atomic_inc(&lc->io_blocks); + bio = bio_alloc(GFP_KERNEL, min(block->vec_cnt, BIO_MAX_PAGES)); if (!bio) { DMERR("Couldn't alloc log bio"); goto error; } - atomic_inc(&lc->io_blocks); bio->bi_iter.bi_size = 0; bio->bi_iter.bi_sector = sector; bio->bi_bdev = lc->logdev->bdev; @@ -280,7 +280,7 @@ static int log_one_block(struct log_writ if (ret != block->vecs[i].bv_len) { atomic_inc(&lc->io_blocks); submit_bio(WRITE, bio); - bio = bio_alloc(GFP_KERNEL, block->vec_cnt - i); + bio = bio_alloc(GFP_KERNEL, min(block->vec_cnt - i, BIO_MAX_PAGES)); if (!bio) { DMERR("Couldn't alloc log bio"); goto error; -- dm-devel mailing list [email protected] https://www.redhat.com/mailman/listinfo/dm-devel
