btrfs: Introduce btrfs_io_geometry infrastructure
Add a structure that holds various parameters for IO calculations and a
helper that fills the values. This will help further refactoring and
reduction of functions that in some way open-coded the calculations.
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 4181381..7934946 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -5915,6 +5915,102 @@ static bool need_full_stripe(enum btrfs_map_op op)
return (op == BTRFS_MAP_WRITE || op == BTRFS_MAP_GET_READ_MIRRORS);
}
+/*
+ * btrfs_get_io_geometry - calculates the geomery of a particular (address, len)
+ * tuple. This information is used to calculate how big a
+ * particular bio can get before it straddles a stripe.
+ *
+ * @fs_info - the filesystem
+ * @logical - address that we want to figure out the geometry of
+ * @len - the length of IO we are going to perform, starting at @logical
+ * @op - type of operation - write or read
+ * @io_geom - pointer used to return values
+ *
+ * Returns < 0 in case a chunk for the given logical address cannot be found,
+ * usually shouldn't happen unless @logical is corrupted, 0 otherwise.
+ */
+int btrfs_get_io_geometry(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
+ u64 logical, u64 len, struct btrfs_io_geometry *io_geom)
+{
+ struct extent_map *em;
+ struct map_lookup *map;
+ u64 offset;
+ u64 stripe_offset;
+ u64 stripe_nr;
+ u64 stripe_len;
+ u64 raid56_full_stripe_start = (u64)-1;
+ int data_stripes;
+
+ ASSERT(op != BTRFS_MAP_DISCARD);
+
+ em = btrfs_get_chunk_map(fs_info, logical, len);
+ if (IS_ERR(em))
+ return PTR_ERR(em);
+
+ map = em->map_lookup;
+ /* Offset of this logical address in the chunk */
+ offset = logical - em->start;
+ /* Len of a stripe in a chunk */
+ stripe_len = map->stripe_len;
+ /* Stripe wher this block falls in */
+ stripe_nr = div64_u64(offset, stripe_len);
+ /* Offset of stripe in the chunk */
+ stripe_offset = stripe_nr * stripe_len;
+ if (offset < stripe_offset) {
+ btrfs_crit(fs_info,
+"stripe math has gone wrong, stripe_offset=%llu offset=%llu start=%llu logical=%llu stripe_len=%llu",
+ stripe_offset, offset, em->start, logical, stripe_len);
+ free_extent_map(em);
+ return -EINVAL;
+ }
+
+ /* stripe_offset is the offset of this block in its stripe */
+ stripe_offset = offset - stripe_offset;
+ data_stripes = nr_data_stripes(map);
+
+ if (map->type & BTRFS_BLOCK_GROUP_PROFILE_MASK) {
+ u64 max_len = stripe_len - stripe_offset;
+
+ /*
+ * In case of raid56, we need to know the stripe aligned start
+ */
+ if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
+ unsigned long full_stripe_len = stripe_len * data_stripes;
+ raid56_full_stripe_start = offset;
+
+ /*
+ * Allow a write of a full stripe, but make sure we
+ * don't allow straddling of stripes
+ */
+ raid56_full_stripe_start = div64_u64(raid56_full_stripe_start,
+ full_stripe_len);
+ raid56_full_stripe_start *= full_stripe_len;
+
+ /*
+ * For writes to RAID[56], allow a full stripeset across
+ * all disks. For other RAID types and for RAID[56]
+ * reads, just allow a single stripe (on a single disk).
+ */
+ if (op == BTRFS_MAP_WRITE) {
+ max_len = stripe_len * data_stripes -
+ (offset - raid56_full_stripe_start);
+ }
+ }
+ len = min_t(u64, em->len - offset, max_len);
+ } else {
+ len = em->len - offset;
+ }
+
+ io_geom->len = len;
+ io_geom->offset = offset;
+ io_geom->stripe_len = stripe_len;
+ io_geom->stripe_nr = stripe_nr;
+ io_geom->stripe_offset = stripe_offset;
+ io_geom->raid56_stripe_offset = raid56_full_stripe_start;
+
+ return 0;
+}
+
static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
enum btrfs_map_op op,
u64 logical, u64 *length,
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index fea7b65..2a8e398 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -23,6 +23,21 @@ struct btrfs_pending_bios {
struct bio *tail;
};
+struct btrfs_io_geometry {
+ /* remaining bytes before crossing a stripe */
+ u64 len;
+ /* offset of logical address in chunk */
+ u64 offset;
+ /* length of single IO stripe */
+ u64 stripe_len;
+ /* number of stripe where address falls */
+ u64 stripe_nr;
+ /* offset of address in stripe */
+ u64 stripe_offset;
+ /* offset of raid56 stripe into the chunk */
+ u64 raid56_stripe_offset;
+};
+
/*
* Use sequence counter to get consistent device stat data on
* 32-bit processors.
@@ -413,6 +428,8 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
int btrfs_map_sblock(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
u64 logical, u64 *length,
struct btrfs_bio **bbio_ret);
+int btrfs_get_io_geometry(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
+ u64 logical, u64 len, struct btrfs_io_geometry *io_geom);
int btrfs_rmap_block(struct btrfs_fs_info *fs_info, u64 chunk_start,
u64 physical, u64 **logical, int *naddrs, int *stripe_len);
int btrfs_read_sys_array(struct btrfs_fs_info *fs_info);
