dm: factor out max_io_len_target_boundary

Split max_io_len_target_boundary out of max_io_len so that the discard
support can make use of it without duplicating max_io_len code.

Avoiding max_io_len's split_io logic enables DM's discard support to
submit the entire discard request to a target.  But discards must still
be split on target boundaries.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 3dd846e..561313a 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1030,17 +1030,27 @@ static void end_clone_request(struct request *clone, int error)
        dm_complete_request(clone, error);
 }
 
-static sector_t max_io_len(struct mapped_device *md,
-                          sector_t sector, struct dm_target *ti)
+/*
+ * Return maximum size of I/O possible at the supplied sector up to the current
+ * target boundary.
+ */
+static sector_t max_io_len_target_boundary(sector_t sector, struct dm_target *ti)
+{
+       sector_t target_offset = dm_target_offset(ti, sector);
+
+       return ti->len - target_offset;
+}
+
+static sector_t max_io_len(sector_t sector, struct dm_target *ti)
 {
-       sector_t offset = sector - ti->begin;
-       sector_t len = ti->len - offset;
+       sector_t len = max_io_len_target_boundary(sector, ti);
 
        /*
         * Does the target need to split even further ?
         */
        if (ti->split_io) {
                sector_t boundary;
+               sector_t offset = dm_target_offset(ti, sector);
                boundary = ((offset + ti->split_io) & ~(ti->split_io - 1))
                           - offset;
                if (len > boundary)
@@ -1258,7 +1268,7 @@ static int __clone_and_map_discard(struct clone_info *ci)
        if (!ti->num_discard_requests)
                return -EOPNOTSUPP;
 
-       max = max_io_len(ci->md, ci->sector, ti);
+       max = max_io_len(ci->sector, ti);
 
        if (ci->sector_count > max)
                /*
@@ -1290,7 +1300,7 @@ static int __clone_and_map(struct clone_info *ci)
        if (!dm_target_is_valid(ti))
                return -EIO;
 
-       max = max_io_len(ci->md, ci->sector, ti);
+       max = max_io_len(ci->sector, ti);
 
        if (ci->sector_count <= max) {
                /*
@@ -1341,7 +1351,7 @@ static int __clone_and_map(struct clone_info *ci)
                                if (!dm_target_is_valid(ti))
                                        return -EIO;
 
-                               max = max_io_len(ci->md, ci->sector, ti);
+                               max = max_io_len(ci->sector, ti);
                        }
 
                        len = min(remaining, max);
@@ -1428,7 +1438,7 @@ static int dm_merge_bvec(struct request_queue *q,
        /*
         * Find maximum amount of I/O that won't need splitting
         */
-       max_sectors = min(max_io_len(md, bvm->bi_sector, ti),
+       max_sectors = min(max_io_len(bvm->bi_sector, ti),
                          (sector_t) BIO_MAX_SECTORS);
        max_size = (max_sectors << SECTOR_SHIFT) - bvm->bi_size;
        if (max_size < 0)

diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 751ce21..2970022 100644 (file)
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -398,6 +398,12 @@ void *dm_vcalloc(unsigned long nmemb, unsigned long elem_size);
 #define dm_array_too_big(fixed, obj, num) \
        ((num) > (UINT_MAX - (fixed)) / (obj))
 
+/*
+ * Sector offset taken relative to the start of the target instead of
+ * relative to the start of the device.
+ */
+#define dm_target_offset(ti, sector) ((sector) - (ti)->begin)
+
 static inline sector_t to_sector(unsigned long n)
 {
        return (n >> SECTOR_SHIFT);