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ore: Support for short read/writes

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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: Boaz Harrosh <bharrosh@panasas.com>
This commit is contained in:
Boaz Harrosh 2011-08-26 21:04:52 -07:00
parent 154a9300cd
commit bbf9a31bba
1 changed files with 23 additions and 7 deletions
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30
fs/exofs/ore.c
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@ -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;
return ret;
if (unlikely(ret)) {
if (length == ios->length)
return ret;
else
ios->length -= length;
}
return 0;
}
int ore_create(struct ore_io_state *ios)