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block: allow large discard requests 

Currently we set the bio size to the byte equivalent of the blocks to
be trimmed when submitting the initial DISCARD ioctl.  That means it
is subject to the max_hw_sectors limitation of the HBA which is
much lower than the size of a DISCARD request we can support.
Add a separate max_discard_sectors tunable to limit the size for discard
requests.

We limit the max discard request size in bytes to 32bit as that is the
limit for bio->bi_size.  This could be much larger if we had a way to pass
that information through the block layer.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Christoph Hellwig 2009-09-30 13:54:20 +02:00 committed by Jens Axboe
parent 1122a26f2a
commit ca80650cfb
4 changed files with 24 additions and 5 deletions
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10
block/blk-barrier.c
View File

@ -385,6 +385,8 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
while (nr_sects && !ret) {
unsigned int sector_size = q->limits.logical_block_size;
unsigned int max_discard_sectors =
min(q->limits.max_discard_sectors, UINT_MAX >> 9);
bio = bio_alloc(gfp_mask, 1);
if (!bio)
@ -411,10 +413,10 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
* touch many more blocks on disk than the actual payload
* length.
*/
if (nr_sects > queue_max_hw_sectors(q)) {
bio->bi_size = queue_max_hw_sectors(q) << 9;
nr_sects -= queue_max_hw_sectors(q);
sector += queue_max_hw_sectors(q);
if (nr_sects > max_discard_sectors) {
bio->bi_size = max_discard_sectors << 9;
nr_sects -= max_discard_sectors;
sector += max_discard_sectors;
} else {
bio->bi_size = nr_sects << 9;
nr_sects = 0;

3
block/blk-core.c
View File

@ -1436,7 +1436,8 @@ static inline void __generic_make_request(struct bio *bio)
goto end_io;
}
if (unlikely(nr_sectors > queue_max_hw_sectors(q))) {
if (unlikely(!bio_rw_flagged(bio, BIO_RW_DISCARD) &&
nr_sectors > queue_max_hw_sectors(q))) {
printk(KERN_ERR "bio too big device %s (%u > %u)\n",
bdevname(bio->bi_bdev, b),
bio_sectors(bio),

13
block/blk-settings.c
View File

@ -96,6 +96,7 @@ void blk_set_default_limits(struct queue_limits *lim)
lim->max_segment_size = MAX_SEGMENT_SIZE;
lim->max_sectors = BLK_DEF_MAX_SECTORS;
lim->max_hw_sectors = INT_MAX;
lim->max_discard_sectors = SAFE_MAX_SECTORS;
lim->logical_block_size = lim->physical_block_size = lim->io_min = 512;
lim->bounce_pfn = (unsigned long)(BLK_BOUNCE_ANY >> PAGE_SHIFT);
lim->alignment_offset = 0;
@ -238,6 +239,18 @@ void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_sectors)
}
EXPORT_SYMBOL(blk_queue_max_hw_sectors);
/**
* blk_queue_max_discard_sectors - set max sectors for a single discard
* @q: the request queue for the device
* @max_discard: maximum number of sectors to discard
**/
void blk_queue_max_discard_sectors(struct request_queue *q,
unsigned int max_discard_sectors)
{
q->limits.max_discard_sectors = max_discard_sectors;
}
EXPORT_SYMBOL(blk_queue_max_discard_sectors);
/**
* blk_queue_max_phys_segments - set max phys segments for a request for this queue
* @q: the request queue for the device

3
include/linux/blkdev.h
View File

@ -311,6 +311,7 @@ struct queue_limits {
unsigned int alignment_offset;
unsigned int io_min;
unsigned int io_opt;
unsigned int max_discard_sectors;
unsigned short logical_block_size;
unsigned short max_hw_segments;
@ -928,6 +929,8 @@ extern void blk_queue_max_hw_sectors(struct request_queue *, unsigned int);
extern void blk_queue_max_phys_segments(struct request_queue *, unsigned short);
extern void blk_queue_max_hw_segments(struct request_queue *, unsigned short);
extern void blk_queue_max_segment_size(struct request_queue *, unsigned int);
extern void blk_queue_max_discard_sectors(struct request_queue *q,
unsigned int max_discard_sectors);
extern void blk_queue_logical_block_size(struct request_queue *, unsigned short);
extern void blk_queue_physical_block_size(struct request_queue *, unsigned short);
extern void blk_queue_alignment_offset(struct request_queue *q,