dm: split discards further if target sets max_discard_granularity

The block core (bio_split_discard) will already split discards based
on the 'discard_granularity' and 'max_discard_sectors' queue_limits.
But the DM thin target also needs to ensure that it doesn't receive a
discard that spans a 'max_discard_sectors' boundary.

Introduce a dm_target 'max_discard_granularity' flag that if set will
cause DM core to split discard bios relative to 'max_discard_sectors'.
This treats 'discard_granularity' as a "min_discard_granularity" and
'max_discard_sectors' as a "max_discard_granularity".

Requested-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index dfde008..20c6b72 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1162,7 +1162,8 @@ static inline sector_t max_io_len_target_boundary(struct dm_target *ti,
        return ti->len - target_offset;
 }
 
-static sector_t max_io_len(struct dm_target *ti, sector_t sector)
+static sector_t __max_io_len(struct dm_target *ti, sector_t sector,
+                            unsigned int max_granularity)
 {
        sector_t target_offset = dm_target_offset(ti, sector);
        sector_t len = max_io_len_target_boundary(ti, target_offset);
@@ -1173,11 +1174,16 @@ static sector_t max_io_len(struct dm_target *ti, sector_t sector)
         *   explains why stacked chunk_sectors based splitting via
         *   bio_split_to_limits() isn't possible here.
         */
-       if (!ti->max_io_len)
+       if (!max_granularity)
                return len;
        return min_t(sector_t, len,
                min(queue_max_sectors(ti->table->md->queue),
-                   blk_chunk_sectors_left(target_offset, ti->max_io_len)));
+                   blk_chunk_sectors_left(target_offset, max_granularity)));
+}
+
+static inline sector_t max_io_len(struct dm_target *ti, sector_t sector)
+{
+       return __max_io_len(ti, sector, ti->max_io_len);
 }
 
 int dm_set_target_max_io_len(struct dm_target *ti, sector_t len)
@@ -1565,12 +1571,13 @@ static void __send_empty_flush(struct clone_info *ci)
 }
 
 static void __send_changing_extent_only(struct clone_info *ci, struct dm_target *ti,
-                                       unsigned int num_bios)
+                                       unsigned int num_bios,
+                                       unsigned int max_granularity)
 {
        unsigned int len, bios;
 
        len = min_t(sector_t, ci->sector_count,
-                   max_io_len_target_boundary(ti, dm_target_offset(ti, ci->sector)));
+                   __max_io_len(ti, ci->sector, max_granularity));
 
        atomic_add(num_bios, &ci->io->io_count);
        bios = __send_duplicate_bios(ci, ti, num_bios, &len);
@@ -1606,10 +1613,16 @@ static blk_status_t __process_abnormal_io(struct clone_info *ci,
                                          struct dm_target *ti)
 {
        unsigned int num_bios = 0;
+       unsigned int max_granularity = 0;
 
        switch (bio_op(ci->bio)) {
        case REQ_OP_DISCARD:
                num_bios = ti->num_discard_bios;
+               if (ti->max_discard_granularity) {
+                       struct queue_limits *limits =
+                               dm_get_queue_limits(ti->table->md);
+                       max_granularity = limits->max_discard_sectors;
+               }
                break;
        case REQ_OP_SECURE_ERASE:
                num_bios = ti->num_secure_erase_bios;
@@ -1630,7 +1643,7 @@ static blk_status_t __process_abnormal_io(struct clone_info *ci,
        if (unlikely(!num_bios))
                return BLK_STS_NOTSUPP;
 
-       __send_changing_extent_only(ci, ti, num_bios);
+       __send_changing_extent_only(ci, ti, num_bios, max_granularity);
        return BLK_STS_OK;
 }
 

diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 7975483..8aa6b3e 100644 (file)
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -359,6 +359,12 @@ struct dm_target {
        bool discards_supported:1;
 
        /*
+        * Set if this target requires that discards be split on both
+        * 'discard_granularity' and 'max_discard_sectors' boundaries.
+        */
+       bool max_discard_granularity:1;
+
+       /*
         * Set if we need to limit the number of in-flight bios when swapping.
         */
        bool limit_swap_bios:1;

diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h
index 7edf335..1990b57 100644 (file)
--- a/include/uapi/linux/dm-ioctl.h
+++ b/include/uapi/linux/dm-ioctl.h
@@ -286,9 +286,9 @@ enum {
 #define DM_DEV_SET_GEOMETRY    _IOWR(DM_IOCTL, DM_DEV_SET_GEOMETRY_CMD, struct dm_ioctl)
 
 #define DM_VERSION_MAJOR       4
-#define DM_VERSION_MINOR       47
+#define DM_VERSION_MINOR       48
 #define DM_VERSION_PATCHLEVEL  0
-#define DM_VERSION_EXTRA       "-ioctl (2022-07-28)"
+#define DM_VERSION_EXTRA       "-ioctl (2023-03-01)"
 
 /* Status bits */
 #define DM_READONLY_FLAG       (1 << 0) /* In/Out */