From c15227de132f1295f3db6b7df9079956b1020fd8 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@infradead.org>
Date: Wed, 30 Sep 2009 13:52:12 +0200
Subject: block: use normal I/O path for discard requests
prepare_discard_fn() was being called in a place where memory allocation
was effectively impossible. This makes it inappropriate for all but
the most trivial translations of Linux's DISCARD operation to the block
command set. Additionally adding a payload there makes the ownership
of the bio backing unclear as it's now allocated by the device driver
and not the submitter as usual.
It is replaced with QUEUE_FLAG_DISCARD which is used to indicate whether
the queue supports discard operations or not. blkdev_issue_discard now
allocates a one-page, sector-length payload which is the right thing
for the common ATA and SCSI implementations.
The mtd implementation of prepare_discard_fn() is replaced with simply
checking for the request being a discard.
Largely based on a previous patch from Matthew Wilcox <matthew@wil.cx>
which did the prepare_discard_fn but not the different payload allocation
yet.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
block/blk-settings.c | 17 -----------------
1 file changed, 17 deletions(-)
(limited to 'block/blk-settings.c')
diff --git a/block/blk-settings.c b/block/blk-settings.c
index eaf122ff5f16..d29498ef1eb5 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -33,23 +33,6 @@ void blk_queue_prep_rq(struct request_queue *q, prep_rq_fn *pfn)
}
EXPORT_SYMBOL(blk_queue_prep_rq);
-/**
- * blk_queue_set_discard - set a discard_sectors function for queue
- * @q: queue
- * @dfn: prepare_discard function
- *
- * It's possible for a queue to register a discard callback which is used
- * to transform a discard request into the appropriate type for the
- * hardware. If none is registered, then discard requests are failed
- * with %EOPNOTSUPP.
- *
- */
-void blk_queue_set_discard(struct request_queue *q, prepare_discard_fn *dfn)
-{
- q->prepare_discard_fn = dfn;
-}
-EXPORT_SYMBOL(blk_queue_set_discard);
-
/**
* blk_queue_merge_bvec - set a merge_bvec function for queue
* @q: queue
--
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