Using PAGE_SIZE as a minimum expected DMA segment size in consideration
of devices which have a max DMA segment size of < 64k when used on 64k
PAGE_SIZE systems leads to devices not being able to probe such as
eMMC and Exynos UFS controller [0] [1] you can end up with a probe failure
as follows:
WARNING: CPU: 2 PID: 397 at block/blk-settings.c:339 blk_validate_limits+0x364/0x3c0
Ensure we use min(max_seg_size, seg_boundary_mask + 1) as the new min segment
size when max segment size is < PAGE_SIZE for 16k and 64k base page size systems.
If anyone need to backport this patch, the following commits are depended:
commit 6aeb4f836480 ("block: remove bio_add_pc_page")
commit 02ee5d69e3ba ("block: remove blk_rq_bio_prep")
commit b7175e24d6ac ("block: add a dma mapping iterator")
Link: https://lore.kernel.org/linux-block/20230612203314.17820-1-bvanassche@xxxxxxx/ # [0]
Link: https://lore.kernel.org/linux-block/1d55e942-5150-de4c-3a02-c3d066f87028@xxxxxxx/ # [1]
Cc: Yi Zhang <yi.zhang@xxxxxxxxxx>
Cc: John Garry <john.g.garry@xxxxxxxxxx>
Cc: Keith Busch <kbusch@xxxxxxxxxx>
Tested-by: Paul Bunyan <pbunyan@xxxxxxxxxx>
Reviewed-by: Daniel Gomez <da.gomez@xxxxxxxxxx>
Reviewed-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx>
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
V5:
- update commit log(Luis Chamberlain, Daniel Gomez)
- move BLK_MIN_SEGMENT_SIZE to private tag(Daniel Gomez)
- add reviewed-by, tested-by tag
V4:
- take Daniel's suggestion to add min_segment_size limit
for avoiding to call into split code in case that max_seg_size
is > PAGE_SIZE
V3:
- rephrase commit log & fix patch style(Christoph)
- more comment log(Christoph)
V2:
- cover bio_split_rw_at()
- add BLK_MIN_SEGMENT_SIZE
block/blk-merge.c | 2 +-
block/blk-settings.c | 14 +++++++++++---
block/blk.h | 9 +++++++--
include/linux/blkdev.h | 1 +
4 files changed, 20 insertions(+), 6 deletions(-)
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 15cd231d560c..4fe2dfabfc9d 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -329,7 +329,7 @@ int bio_split_rw_at(struct bio *bio, const struct queue_limits *lim,
if (nsegs < lim->max_segments &&
bytes + bv.bv_len <= max_bytes &&
- bv.bv_offset + bv.bv_len <= PAGE_SIZE) {
+ bv.bv_offset + bv.bv_len <= lim->min_segment_size) {
nsegs++;
bytes += bv.bv_len;
} else {
diff --git a/block/blk-settings.c b/block/blk-settings.c
index c44dadc35e1e..b9c6f0ec1c49 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -246,6 +246,7 @@ int blk_validate_limits(struct queue_limits *lim)
{
unsigned int max_hw_sectors;
unsigned int logical_block_sectors;
+ unsigned long seg_size;
int err;
/*
@@ -303,7 +304,7 @@ int blk_validate_limits(struct queue_limits *lim)
max_hw_sectors = min_not_zero(lim->max_hw_sectors,
lim->max_dev_sectors);
if (lim->max_user_sectors) {
- if (lim->max_user_sectors < PAGE_SIZE / SECTOR_SIZE)
+ if (lim->max_user_sectors < BLK_MIN_SEGMENT_SIZE / SECTOR_SIZE)
return -EINVAL;
lim->max_sectors = min(max_hw_sectors, lim->max_user_sectors);
} else if (lim->io_opt > (BLK_DEF_MAX_SECTORS_CAP << SECTOR_SHIFT)) {
@@ -341,7 +342,7 @@ int blk_validate_limits(struct queue_limits *lim)
*/
if (!lim->seg_boundary_mask)
lim->seg_boundary_mask = BLK_SEG_BOUNDARY_MASK;
- if (WARN_ON_ONCE(lim->seg_boundary_mask < PAGE_SIZE - 1))
+ if (WARN_ON_ONCE(lim->seg_boundary_mask < BLK_MIN_SEGMENT_SIZE - 1))
return -EINVAL;
/*
@@ -362,10 +363,17 @@ int blk_validate_limits(struct queue_limits *lim)
*/
if (!lim->max_segment_size)
lim->max_segment_size = BLK_MAX_SEGMENT_SIZE;
- if (WARN_ON_ONCE(lim->max_segment_size < PAGE_SIZE))
+ if (WARN_ON_ONCE(lim->max_segment_size < BLK_MIN_SEGMENT_SIZE))
return -EINVAL;
}
+ /* setup min segment size for building new segment in fast path */
+ if (lim->seg_boundary_mask > lim->max_segment_size - 1)
+ seg_size = lim->max_segment_size;
+ else
+ seg_size = lim->seg_boundary_mask + 1;
+ lim->min_segment_size = min_t(unsigned int, seg_size, PAGE_SIZE);
+
/*
* We require drivers to at least do logical block aligned I/O, but
* historically could not check for that due to the separate calls
diff --git a/block/blk.h b/block/blk.h
index 90fa5f28ccab..9cf9a0099416 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -14,6 +14,7 @@
struct elevator_type;
#define BLK_DEV_MAX_SECTORS (LLONG_MAX >> 9)
+#define BLK_MIN_SEGMENT_SIZE 4096
/* Max future timer expiry for timeouts */
#define BLK_MAX_TIMEOUT (5 * HZ)
@@ -358,8 +359,12 @@ struct bio *bio_split_zone_append(struct bio *bio,
static inline bool bio_may_need_split(struct bio *bio,
const struct queue_limits *lim)
{
- return lim->chunk_sectors || bio->bi_vcnt != 1 ||
- bio->bi_io_vec->bv_len + bio->bi_io_vec->bv_offset > PAGE_SIZE;
+ if (lim->chunk_sectors)
+ return true;
+ if (bio->bi_vcnt != 1)
+ return true;
+ return bio->bi_io_vec->bv_len + bio->bi_io_vec->bv_offset >
+ lim->min_segment_size;
}
/**
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 248416ecd01c..58ff5aca83b6 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -367,6 +367,7 @@ struct queue_limits {
unsigned int max_sectors;
unsigned int max_user_sectors;
unsigned int max_segment_size;
+ unsigned int min_segment_size;
unsigned int physical_block_size;
unsigned int logical_block_size;
unsigned int alignment_offset;
--
2.47.1
