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block: allow large discard requests

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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,