On Wed, Nov 09, 2011 at 11:29:31AM +0100, Jan Schmidt wrote:
> Am 09.11.2011 08:48, schrieb Christoph Hellwig:
> >On Tue, Nov 08, 2011 at 08:07:01PM -0500, Chris Mason wrote:
> >>Looks like bio_add_page() is failing and we're getting the enomem from
> >>there. LVM is only letting us put one page in each bio.
> >
> >Yes, at the moment all bio based DM targets only allow single page I/O.
>
> Wait. If I got that correctly, each bio_add_page needs special
> ENOMEM treatment (assuming the target could always be a device
> mapper target), right?
Each bio_add_page caller needs to expect it can't add more than a
page worth of data. If you look at callers what write large amounts
of data (XFS, mpage code) you'll always see a pattern of:
bio = bio_alloc();
while (bytes_left) {
len = min(bytes_left, PAGE_SIZE);
bytes = bio_add_page(io, ..., len);
if (bytes < len) {
submit_bio(bio);
bio = bio_alloc();
}
update_indices();
}
submit_bio(bio);
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
