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 <mpatocka@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # 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;
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