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>

diff --git a/block/blk-barrier.c b/block/blk-barrier.c
index 21f5025c3945053d4b6cae40d5eac9b614b9a55b..8873b9b439ffdb0bf695b0077f84bb28c1046a38 100644 (file)
--- a/block/blk-barrier.c
+++ b/block/blk-barrier.c
@@ -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;

diff --git a/block/blk-core.c b/block/blk-core.c
index 80a020dd1580e43c77221792a6fb981fb3cb2533..34504f30972831484c7285a9edd30add2d3b1bca 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -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),

diff --git a/block/blk-settings.c b/block/blk-settings.c
index d29498ef1eb559a39ff824347daef9a03762d324..e0695bca702777d7455e9d4266590be47977443e 100644 (file)
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -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

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index f62d45e87618d1a4c389b1e3229fd90a42202bb4..1a03b715dfad418ef8c515674dc78bb94890a3e7 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -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,