md/raid1-10: add a helper raid1_check_read_range()

The checking and handler of bad blocks appear many timers during
read_balance() in raid1 and raid10. This helper will be used in later
patches to simplify read_balance() a lot.

Co-developed-by: Paul Luse <paul.e.luse@linux.intel.com>
Signed-off-by: Paul Luse <paul.e.luse@linux.intel.com>
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Xiao Ni <xni@redhat.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20240229095714.926789-6-yukuai1@huaweicloud.com

diff --git a/drivers/md/raid1-10.c b/drivers/md/raid1-10.c
index 512746551f36a754d9e655f220f260b6896dcd10..9bc0f0022a6c11a0432c549806d3d64d2d549509 100644 (file)
--- a/drivers/md/raid1-10.c
+++ b/drivers/md/raid1-10.c
@@ -227,3 +227,52 @@ static inline bool exceed_read_errors(struct mddev *mddev, struct md_rdev *rdev)
 
        return false;
 }
+
+/**
+ * raid1_check_read_range() - check a given read range for bad blocks,
+ * available read length is returned;
+ * @rdev: the rdev to read;
+ * @this_sector: read position;
+ * @len: read length;
+ *
+ * helper function for read_balance()
+ *
+ * 1) If there are no bad blocks in the range, @len is returned;
+ * 2) If the range are all bad blocks, 0 is returned;
+ * 3) If there are partial bad blocks:
+ *  - If the bad block range starts after @this_sector, the length of first
+ *  good region is returned;
+ *  - If the bad block range starts before @this_sector, 0 is returned and
+ *  the @len is updated to the offset into the region before we get to the
+ *  good blocks;
+ */
+static inline int raid1_check_read_range(struct md_rdev *rdev,
+                                        sector_t this_sector, int *len)
+{
+       sector_t first_bad;
+       int bad_sectors;
+
+       /* no bad block overlap */
+       if (!is_badblock(rdev, this_sector, *len, &first_bad, &bad_sectors))
+               return *len;
+
+       /*
+        * bad block range starts offset into our range so we can return the
+        * number of sectors before the bad blocks start.
+        */
+       if (first_bad > this_sector)
+               return first_bad - this_sector;
+
+       /* read range is fully consumed by bad blocks. */
+       if (this_sector + *len <= first_bad + bad_sectors)
+               return 0;
+
+       /*
+        * final case, bad block range starts before or at the start of our
+        * range but does not cover our entire range so we still return 0 but
+        * update the length with the number of sectors before we get to the
+        * good ones.
+        */
+       *len = first_bad + bad_sectors - this_sector;
+       return 0;
+}