logfs: query block device for number of pages to send with bio
The block device driver puts a limit on maximum number of pages that
can be sent with the bio. Not all block devices can handle
BIO_MAX_PAGES number of pages in bio. Specifically the virtio-blk
diriver limits it to 126. When the LogFS file system was excersized in
KVM, the following bug from do_virtblk_request() was observed
static void do_virtblk_request(struct request_queue *q)
{
....
....
while ((req = blk_peek_request(q)) != NULL) {
BUG_ON(req->nr_phys_segments + 2 > vblk->sg_elems);
....
....
}
....
}
The patch fixes the problem by querring the maximum number of pages in
bio allowed from block device driver and then using those many pages
during submit_bio.
Signed-off-by: Prasad Joshi <prasadjoshi.linux@gmail.com>
1 file changed