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authorMikulas Patocka <mpatocka@redhat.com>2012-12-21 20:23:38 +0000
committerAlasdair G Kergon <agk@redhat.com>2012-12-21 20:23:38 +0000
commitc0820cf5ad09522bdd9ff68e84841a09c9f339d8 (patch)
tree04817d6d9a7d213ac96d1e014a9714f8f29ff07a /include
parent70d6c400acc386ea910c77318688541fc32e7ce8 (diff)
dm: introduce per_bio_data
Introduce a field per_bio_data_size in struct dm_target. Targets can set this field in the constructor. If a target sets this field to a non-zero value, "per_bio_data_size" bytes of auxiliary data are allocated for each bio submitted to the target. These data can be used for any purpose by the target and help us improve performance by removing some per-target mempools. Per-bio data is accessed with dm_per_bio_data. The argument data_size must be the same as the value per_bio_data_size in dm_target. If the target has a pointer to per_bio_data, it can get a pointer to the bio with dm_bio_from_per_bio_data() function (data_size must be the same as the value passed to dm_per_bio_data). Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'include')
-rw-r--r--include/linux/device-mapper.h30
1 files changed, 30 insertions, 0 deletions
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index d1f6cd8486f..6f0e73b4a80 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -210,6 +210,12 @@ struct dm_target {
*/
unsigned num_write_same_requests;
+ /*
+ * The minimum number of extra bytes allocated in each bio for the
+ * target to use. dm_per_bio_data returns the data location.
+ */
+ unsigned per_bio_data_size;
+
/* target specific data */
void *private;
@@ -246,6 +252,30 @@ struct dm_target_callbacks {
int (*congested_fn) (struct dm_target_callbacks *, int);
};
+/*
+ * For bio-based dm.
+ * One of these is allocated for each bio.
+ * This structure shouldn't be touched directly by target drivers.
+ * It is here so that we can inline dm_per_bio_data and
+ * dm_bio_from_per_bio_data
+ */
+struct dm_target_io {
+ struct dm_io *io;
+ struct dm_target *ti;
+ union map_info info;
+ struct bio clone;
+};
+
+static inline void *dm_per_bio_data(struct bio *bio, size_t data_size)
+{
+ return (char *)bio - offsetof(struct dm_target_io, clone) - data_size;
+}
+
+static inline struct bio *dm_bio_from_per_bio_data(void *data, size_t data_size)
+{
+ return (struct bio *)((char *)data + data_size + offsetof(struct dm_target_io, clone));
+}
+
int dm_register_target(struct target_type *t);
void dm_unregister_target(struct target_type *t);