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SubjectRe: [PATCH] block: remove artifical max_hw_sectors cap
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On Sat, Sep 06, 2014 at 04:08:05PM -0700, Christoph Hellwig wrote:
> 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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---end quoted text---


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