md/raid1: factor out choose_bb_rdev() from read_balance()

read_balance() is hard to understand because there are too many status
and branches, and it's overlong.

This patch factor out the case to read the rdev with bad blocks from
read_balance(), there are no functional changes.

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/20240229095714.926789-10-yukuai1@huaweicloud.com

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 09b7e93a54b5660a5bfa67114123187c33b6edca..f6e75c123e5aef9450ae8d10ce003d738bf8cc40 100644 (file)
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -620,6 +620,44 @@ static int choose_first_rdev(struct r1conf *conf, struct r1bio *r1_bio,
        return -1;
 }
 
+static int choose_bb_rdev(struct r1conf *conf, struct r1bio *r1_bio,
+                         int *max_sectors)
+{
+       sector_t this_sector = r1_bio->sector;
+       int best_disk = -1;
+       int best_len = 0;
+       int disk;
+
+       for (disk = 0 ; disk < conf->raid_disks * 2 ; disk++) {
+               struct md_rdev *rdev;
+               int len;
+               int read_len;
+
+               if (r1_bio->bios[disk] == IO_BLOCKED)
+                       continue;
+
+               rdev = conf->mirrors[disk].rdev;
+               if (!rdev || test_bit(Faulty, &rdev->flags) ||
+                   test_bit(WriteMostly, &rdev->flags))
+                       continue;
+
+               /* keep track of the disk with the most readable sectors. */
+               len = r1_bio->sectors;
+               read_len = raid1_check_read_range(rdev, this_sector, &len);
+               if (read_len > best_len) {
+                       best_disk = disk;
+                       best_len = read_len;
+               }
+       }
+
+       if (best_disk != -1) {
+               *max_sectors = best_len;
+               update_read_sectors(conf, best_disk, this_sector, best_len);
+       }
+
+       return best_disk;
+}
+
 static int choose_slow_rdev(struct r1conf *conf, struct r1bio *r1_bio,
                            int *max_sectors)
 {
@@ -708,8 +746,6 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
 
        for (disk = 0 ; disk < conf->raid_disks * 2 ; disk++) {
                sector_t dist;
-               sector_t first_bad;
-               int bad_sectors;
                unsigned int pending;
 
                rdev = conf->mirrors[disk].rdev;
@@ -722,36 +758,8 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
                        continue;
                if (test_bit(WriteMostly, &rdev->flags))
                        continue;
-               /* This is a reasonable device to use.  It might
-                * even be best.
-                */
-               if (is_badblock(rdev, this_sector, sectors,
-                               &first_bad, &bad_sectors)) {
-                       if (best_dist < MaxSector)
-                               /* already have a better device */
-                               continue;
-                       if (first_bad <= this_sector) {
-                               /* cannot read here. If this is the 'primary'
-                                * device, then we must not read beyond
-                                * bad_sectors from another device..
-                                */
-                               bad_sectors -= (this_sector - first_bad);
-                               if (best_good_sectors > sectors)
-                                       best_good_sectors = sectors;
-
-                       } else {
-                               sector_t good_sectors = first_bad - this_sector;
-                               if (good_sectors > best_good_sectors) {
-                                       best_good_sectors = good_sectors;
-                                       best_disk = disk;
-                               }
-                       }
+               if (rdev_has_badblock(rdev, this_sector, sectors))
                        continue;
-               } else {
-                       if ((sectors > best_good_sectors) && (best_disk >= 0))
-                               best_disk = -1;
-                       best_good_sectors = sectors;
-               }
 
                if (best_disk >= 0)
                        /* At least two disks to choose from so failfast is OK */
@@ -843,6 +851,15 @@ static int read_balance(struct r1conf *conf, struct r1bio *r1_bio, int *max_sect
        if (best_disk >= 0)
                return best_disk;
 
+       /*
+        * If we are here it means we didn't find a perfectly good disk so
+        * now spend a bit more time trying to find one with the most good
+        * sectors.
+        */
+       disk = choose_bb_rdev(conf, r1_bio, max_sectors);
+       if (disk >= 0)
+               return disk;
+
        return choose_slow_rdev(conf, r1_bio, max_sectors);
 }