From: Keith Busch <kbusch@xxxxxxxxxx>
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@xxxxxxxxxx>
---
v2->v3:
Added documentation update (Damien)
Using the unsigned BLK_DEF_MAX_SECTORS (Christoph)
Documentation/ABI/stable/sysfs-block | 3 ++-
block/blk-settings.c | 9 +++++++--
block/blk-sysfs.c | 13 ++++++++++---
include/linux/blkdev.h | 1 +
4 files changed, 20 insertions(+), 6 deletions(-)
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@xxxxxxxxxxxxxxx
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..e67acd859d072 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -249,9 +249,16 @@ queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
max_hw_sectors_kb = min_not_zero(max_hw_sectors_kb, (unsigned long)
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 69f7199d38da8..8f5bb00d12ece 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;
--
2.30.2
