From bbf9a31bba8c985780fe94da059cc5813a7920f5 Mon Sep 17 00:00:00 2001 From: Boaz Harrosh Date: Fri, 26 Aug 2011 21:04:52 -0700 Subject: [PATCH] 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: Boaz Harrosh --- fs/exofs/ore.c | 30 +++++++++++++++++++++++------- 1 file changed, 23 insertions(+), 7 deletions(-) diff --git a/fs/exofs/ore.c b/fs/exofs/ore.c index d0f8db5e46c5..8354fe061d1c 100644 --- a/fs/exofs/ore.c +++ b/fs/exofs/ore.c @@ -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) -- 2.34.1