diff mbox series

[PATCHv4,2/2] block: save user max_sectors limit

Message ID 20230105205146.3610282-3-kbusch@meta.com (mailing list archive)
State New, archived
Headers show
Series block: don't forget user settings | expand

Commit Message

Keith Busch Jan. 5, 2023, 8:51 p.m. UTC 
From: Keith Busch <kbusch@kernel.org>

The user can set the max_sectors limit to any valid value via sysfs
/sys/block/<dev>/queue/max_sectors_kb attribute. If the device limits
are ever rescanned, though, the limit reverts back to the potentially
artificially low BLK_DEF_MAX_SECTORS value.

Preserve the user's setting as the max_sectors limit as long as it's
valid. The user can reset back to defaults by writing 0 to the sysfs
file.

Signed-off-by: Keith Busch <kbusch@kernel.org>
---
 Documentation/ABI/stable/sysfs-block |  3 ++-
 block/blk-settings.c                 |  9 +++++++--
 block/blk-sysfs.c                    | 21 +++++++++++++++------
 include/linux/blkdev.h               |  1 +
 4 files changed, 25 insertions(+), 9 deletions(-)

Comments

Bart Van Assche Jan. 5, 2023, 9:28 p.m. UTC | #1 
On 1/5/23 12:51, Keith Busch wrote:
> diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> index 93d9e9c9a6ea8..5486b6c57f6b8 100644
> --- a/block/blk-sysfs.c
> +++ b/block/blk-sysfs.c
> @@ -239,19 +239,28 @@ static ssize_t queue_zone_append_max_show(struct request_queue *q, char *page)
>   static ssize_t
>   queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
>   {
> -	unsigned long max_sectors_kb,
> +	unsigned long var;
> +	unsigned int max_sectors_kb,
>   		max_hw_sectors_kb = queue_max_hw_sectors(q) >> 1,
>   			page_kb = 1 << (PAGE_SHIFT - 10);
> -	ssize_t ret = queue_var_store(&max_sectors_kb, page, count);
> +	ssize_t ret = queue_var_store(&var, page, count);
>   
>   	if (ret < 0)
>   		return ret;
>   
> -	max_hw_sectors_kb = min_not_zero(max_hw_sectors_kb, (unsigned long)
> +	max_sectors_kb = (unsigned int)var;

Shouldn't this function report an error if 'var' is too large to fit 
into an unsigned int?

Otherwise this patch looks good to me.

Thanks,

Bart.
Keith Busch Jan. 5, 2023, 9:36 p.m. UTC | #2 
On Thu, Jan 05, 2023 at 01:28:35PM -0800, Bart Van Assche wrote:
> On 1/5/23 12:51, Keith Busch wrote:
> > diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> > index 93d9e9c9a6ea8..5486b6c57f6b8 100644
> > --- a/block/blk-sysfs.c
> > +++ b/block/blk-sysfs.c
> > @@ -239,19 +239,28 @@ static ssize_t queue_zone_append_max_show(struct request_queue *q, char *page)
> >   static ssize_t
> >   queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
> >   {
> > -	unsigned long max_sectors_kb,
> > +	unsigned long var;
> > +	unsigned int max_sectors_kb,
> >   		max_hw_sectors_kb = queue_max_hw_sectors(q) >> 1,
> >   			page_kb = 1 << (PAGE_SHIFT - 10);
> > -	ssize_t ret = queue_var_store(&max_sectors_kb, page, count);
> > +	ssize_t ret = queue_var_store(&var, page, count);
> >   	if (ret < 0)
> >   		return ret;
> > -	max_hw_sectors_kb = min_not_zero(max_hw_sectors_kb, (unsigned long)
> > +	max_sectors_kb = (unsigned int)var;
> 
> Shouldn't this function report an error if 'var' is too large to fit into an
> unsigned int?

Yes it should, and queue_var_store() will return -EINVAL if that
happens. That's certainly not clear just from reading this patch, but
the condition is handled.
Christoph Hellwig Jan. 8, 2023, 5:13 p.m. UTC | #3 
Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>
Martin K. Petersen Jan. 9, 2023, 12:25 a.m. UTC | #4 
Keith,

> The user can set the max_sectors limit to any valid value via sysfs
> /sys/block/<dev>/queue/max_sectors_kb attribute. If the device limits
> are ever rescanned, though, the limit reverts back to the potentially
> artificially low BLK_DEF_MAX_SECTORS value.
>
> Preserve the user's setting as the max_sectors limit as long as it's
> valid. The user can reset back to defaults by writing 0 to the sysfs
> file.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
diff mbox series

Patch

diff --git a/Documentation/ABI/stable/sysfs-block b/Documentation/ABI/stable/sysfs-block
index cd14ecb3c9a5a..ac1e519272aa2 100644
--- a/Documentation/ABI/stable/sysfs-block
+++ b/Documentation/ABI/stable/sysfs-block
@@ -432,7 +432,8 @@  Contact:	linux-block@vger.kernel.org
 Description:
 		[RW] This is the maximum number of kilobytes that the block
 		layer will allow for a filesystem request. Must be smaller than
-		or equal to the maximum size allowed by the hardware.
+		or equal to the maximum size allowed by the hardware. Write 0
+		to use default kernel settings.
 
 
 What:		/sys/block/<disk>/queue/max_segment_size
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 9875ca131eb0c..9c9713c9269cc 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -40,7 +40,7 @@  void blk_set_default_limits(struct queue_limits *lim)
 	lim->virt_boundary_mask = 0;
 	lim->max_segment_size = BLK_MAX_SEGMENT_SIZE;
 	lim->max_sectors = lim->max_hw_sectors = BLK_SAFE_MAX_SECTORS;
-	lim->max_dev_sectors = 0;
+	lim->max_user_sectors = lim->max_dev_sectors = 0;
 	lim->chunk_sectors = 0;
 	lim->max_write_zeroes_sectors = 0;
 	lim->max_zone_append_sectors = 0;
@@ -135,7 +135,12 @@  void blk_queue_max_hw_sectors(struct request_queue *q, unsigned int max_hw_secto
 	limits->max_hw_sectors = max_hw_sectors;
 
 	max_sectors = min_not_zero(max_hw_sectors, limits->max_dev_sectors);
-	max_sectors = min(max_sectors, BLK_DEF_MAX_SECTORS);
+
+	if (limits->max_user_sectors)
+		max_sectors = min(max_sectors, limits->max_user_sectors);
+	else
+		max_sectors = min(max_sectors, BLK_DEF_MAX_SECTORS);
+
 	max_sectors = round_down(max_sectors,
 				 limits->logical_block_size >> SECTOR_SHIFT);
 	limits->max_sectors = max_sectors;
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 93d9e9c9a6ea8..5486b6c57f6b8 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -239,19 +239,28 @@  static ssize_t queue_zone_append_max_show(struct request_queue *q, char *page)
 static ssize_t
 queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
 {
-	unsigned long max_sectors_kb,
+	unsigned long var;
+	unsigned int max_sectors_kb,
 		max_hw_sectors_kb = queue_max_hw_sectors(q) >> 1,
 			page_kb = 1 << (PAGE_SHIFT - 10);
-	ssize_t ret = queue_var_store(&max_sectors_kb, page, count);
+	ssize_t ret = queue_var_store(&var, page, count);
 
 	if (ret < 0)
 		return ret;
 
-	max_hw_sectors_kb = min_not_zero(max_hw_sectors_kb, (unsigned long)
+	max_sectors_kb = (unsigned int)var;
+	max_hw_sectors_kb = min_not_zero(max_hw_sectors_kb,
 					 q->limits.max_dev_sectors >> 1);
-
-	if (max_sectors_kb > max_hw_sectors_kb || max_sectors_kb < page_kb)
-		return -EINVAL;
+	if (max_sectors_kb == 0) {
+		q->limits.max_user_sectors = 0;
+		max_sectors_kb = min(max_hw_sectors_kb,
+				     BLK_DEF_MAX_SECTORS >> 1);
+	} else {
+		if (max_sectors_kb > max_hw_sectors_kb ||
+		    max_sectors_kb < page_kb)
+			return -EINVAL;
+		q->limits.max_user_sectors = max_sectors_kb << 1;
+	}
 
 	spin_lock_irq(&q->queue_lock);
 	q->limits.max_sectors = max_sectors_kb << 1;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 2b85161e22561..b87ed829ab941 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -288,6 +288,7 @@  struct queue_limits {
 	unsigned int		max_dev_sectors;
 	unsigned int		chunk_sectors;
 	unsigned int		max_sectors;
+	unsigned int		max_user_sectors;
 	unsigned int		max_segment_size;
 	unsigned int		physical_block_size;
 	unsigned int		logical_block_size;