Commit bbf9a31b authored by Boaz Harrosh's avatar Boaz Harrosh
Browse files

ore: Support for short read/writes 



Memory conditions and max_bio constraints might cause us to
not comply to the full length of the requested IO. Instead of
failing the complete IO we can issue a shorter read/write and
report how much was actually executed in the ios->length
member.

All users must check ios->length at IO_done or upon return of
ore_read/write and re-issue the reminder of the bytes. Because
other wise there is no error returned like before.

This is part of the effort to support the pnfs-obj layout driver.

Signed-off-by: default avatarBoaz Harrosh <bharrosh@panasas.com>
parent 154a9300

fs/exofs/ore.c

+23 −7
Original line number Diff line number Diff line
@@ -377,8 +377,8 @@ static int _add_stripe_unit(struct ore_io_state *ios, unsigned *cur_pg, 
	unsigned pg = *cur_pg;

	struct request_queue *q =

			osd_request_queue(_ios_od(ios, per_dev->dev));



	per_dev->length += cur_len;

	unsigned len = cur_len;

	int ret;



	if (per_dev->bio == NULL) {

		unsigned pages_in_stripe = ios->layout->group_width *
@@ -390,7 +390,8 @@ static int _add_stripe_unit(struct ore_io_state *ios, unsigned *cur_pg, 
		if (unlikely(!per_dev->bio)) {

			ORE_DBGMSG("Failed to allocate BIO size=%u\n",

				     bio_size);

			return -ENOMEM;

			ret = -ENOMEM;

			goto out;

		}

	}
@@ -403,15 +404,24 @@ static int _add_stripe_unit(struct ore_io_state *ios, unsigned *cur_pg, 


		added_len = bio_add_pc_page(q, per_dev->bio, ios->pages[pg],

					    pglen, pgbase);

		if (unlikely(pglen != added_len))

			return -ENOMEM;

		if (unlikely(pglen != added_len)) {

			ret = -ENOMEM;

			goto out;

		}

		pgbase = 0;

		++pg;

	}

	BUG_ON(cur_len);



	per_dev->length += len;

	*cur_pg = pg;

	return 0;

	ret = 0;

out:	/* we fail the complete unit on an error eg don't advance

	 * per_dev->length and cur_pg. This means that we might have a bigger

	 * bio than the CDB requested length (per_dev->length). That's fine

	 * only the oposite is fatal.

	 */

	return ret;

}



static int _prepare_for_striping(struct ore_io_state *ios)
@@ -472,7 +482,13 @@ static int _prepare_for_striping(struct ore_io_state *ios) 
out:

	ios->numdevs = devs_in_group;

	ios->pages_consumed = cur_pg;

	if (unlikely(ret)) {

		if (length == ios->length)

			return ret;

		else

			ios->length -= length;

	}

	return 0;

}



int ore_create(struct ore_io_state *ios)

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