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Subject[PATCH] block: remove artifical max_hw_sectors cap
Date
Set max_sectors to the value the drivers provides as hardware limit by
default. Linux had proper I/O throttling for a long time and doesn't
rely on a artifically small maximum I/O size anymore. By not limiting
the I/O size by default we remove an annoying tuning step required for
most Linux installation.

Note that both the user, and if absolutely required the driver can still
impose a limit for FS requests below max_hw_sectors_kb.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
block/blk-settings.c | 4 +---
drivers/block/aoe/aoeblk.c | 2 +-
include/linux/blkdev.h | 1 -
3 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/block/blk-settings.c b/block/blk-settings.c
index f1a1795..f52c223 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -257,9 +257,7 @@ void blk_limits_max_hw_sectors(struct queue_limits *limits, unsigned int max_hw_
__func__, max_hw_sectors);
}

- limits->max_hw_sectors = max_hw_sectors;
- limits->max_sectors = min_t(unsigned int, max_hw_sectors,
- BLK_DEF_MAX_SECTORS);
+ limits->max_sectors = limits->max_hw_sectors = max_hw_sectors;
}
EXPORT_SYMBOL(blk_limits_max_hw_sectors);

diff --git a/drivers/block/aoe/aoeblk.c b/drivers/block/aoe/aoeblk.c
index dd73e1f..46c282f 100644
--- a/drivers/block/aoe/aoeblk.c
+++ b/drivers/block/aoe/aoeblk.c
@@ -395,7 +395,7 @@ aoeblk_gdalloc(void *vp)
WARN_ON(d->flags & DEVFL_TKILL);
WARN_ON(d->gd);
WARN_ON(d->flags & DEVFL_UP);
- blk_queue_max_hw_sectors(q, BLK_DEF_MAX_SECTORS);
+ blk_queue_max_hw_sectors(q, 1024);
q->backing_dev_info.name = "aoe";
q->backing_dev_info.ra_pages = READ_AHEAD / PAGE_CACHE_SIZE;
d->bufpool = mp;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 518b465..7e3c172 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1192,7 +1192,6 @@ extern int blk_verify_command(unsigned char *cmd, fmode_t has_write_perm);
enum blk_default_limits {
BLK_MAX_SEGMENTS = 128,
BLK_SAFE_MAX_SECTORS = 255,
- BLK_DEF_MAX_SECTORS = 1024,
BLK_MAX_SEGMENT_SIZE = 65536,
BLK_SEG_BOUNDARY_MASK = 0xFFFFFFFFUL,
};
--
1.9.1


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