dm-table: atomic writes support

Support stacking atomic write limits for DM devices.

All the pre-existing code in blk_stack_atomic_writes_limits() already takes
care of finding the aggregrate limits from the bottom devices.

Feature flag DM_TARGET_ATOMIC_WRITES is introduced so that atomic writes
can be enabled on personalities selectively. This is to ensure that atomic
writes are only enabled when verified to be working properly (for a
specific personality). In addition, it just may not make sense to enable
atomic writes on some personalities (so this flag also helps there).

Signed-off-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index bd8b796ae683bbd2ecb721027c38df2bef096415..0ef5203387b26f96d59235a48f746e96927b196b 100644 (file)
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1806,6 +1806,32 @@ static bool dm_table_supports_secure_erase(struct dm_table *t)
        return true;
 }
 
+static int device_not_atomic_write_capable(struct dm_target *ti,
+                       struct dm_dev *dev, sector_t start,
+                       sector_t len, void *data)
+{
+       return !bdev_can_atomic_write(dev->bdev);
+}
+
+static bool dm_table_supports_atomic_writes(struct dm_table *t)
+{
+       for (unsigned int i = 0; i < t->num_targets; i++) {
+               struct dm_target *ti = dm_table_get_target(t, i);
+
+               if (!dm_target_supports_atomic_writes(ti->type))
+                       return false;
+
+               if (!ti->type->iterate_devices)
+                       return false;
+
+               if (ti->type->iterate_devices(ti,
+                       device_not_atomic_write_capable, NULL)) {
+                       return false;
+               }
+       }
+       return true;
+}
+
 int dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
                              struct queue_limits *limits)
 {
@@ -1854,6 +1880,9 @@ int dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
                        return r;
        }
 
+       if (dm_table_supports_atomic_writes(t))
+               limits->features |= BLK_FEAT_ATOMIC_WRITES;
+
        r = queue_limits_set(q, limits);
        if (r)
                return r;

diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 8321f65897f3d5c7356508ba1f83b291b92881d8..bcc6d7b6947010d10f67300b9efe958c222e1e45 100644 (file)
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -299,6 +299,9 @@ struct target_type {
 #define dm_target_supports_mixed_zoned_model(type) (false)
 #endif
 
+#define DM_TARGET_ATOMIC_WRITES                0x00000400
+#define dm_target_supports_atomic_writes(type) ((type)->features & DM_TARGET_ATOMIC_WRITES)
+
 struct dm_target {
        struct dm_table *table;
        struct target_type *type;

diff --git a/include/uapi/linux/dm-ioctl.h b/include/uapi/linux/dm-ioctl.h
index 1990b5700f6948243def314cec22f380926aca2e..b08c7378164d9e4e5203c907d2868c7633fa15fc 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       48
+#define DM_VERSION_MINOR       49
 #define DM_VERSION_PATCHLEVEL  0
-#define DM_VERSION_EXTRA       "-ioctl (2023-03-01)"
+#define DM_VERSION_EXTRA       "-ioctl (2025-01-17)"
 
 /* Status bits */
 #define DM_READONLY_FLAG       (1 << 0) /* In/Out */