3 files changed, 51 insertions, 17 deletions

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 28a3869dcfd2..0b82030c265d 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1787,7 +1787,6 @@ static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, i
                 bio->bi_vcnt = 0;
                 bio->bi_idx = 0;
                 bio->bi_phys_segments = 0;
-                bio->bi_hw_segments = 0;
                 bio->bi_size = 0;
                 bio->bi_end_io = NULL;
                 bio->bi_private = NULL;
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 0f40688503e7..d3b9aa096285 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1944,7 +1944,6 @@ static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, i
                 bio->bi_vcnt = 0;
                 bio->bi_idx = 0;
                 bio->bi_phys_segments = 0;
-                bio->bi_hw_segments = 0;
                 bio->bi_size = 0;
         }
 
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 224de022e7c5..05b22925cce4 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -101,6 +101,40 @@
 const char raid6_empty_zero_page[PAGE_SIZE] __attribute__((aligned(256)));
 #endif
 
+/*
+ * We maintain a biased count of active stripes in the bottom 8 bits of
+ * bi_phys_segments, and a count of processed stripes in the upper 8 bits
+ */
+static inline int raid5_bi_phys_segments(struct bio *bio)
+{
+        return bio->bi_phys_segments & 0xff;
+}
+
+static inline int raid5_bi_hw_segments(struct bio *bio)
+{
+        return (bio->bi_phys_segments >> 8) & 0xff;
+}
+
+static inline int raid5_dec_bi_phys_segments(struct bio *bio)
+{
+        --bio->bi_phys_segments;
+        return raid5_bi_phys_segments(bio);
+}
+
+static inline int raid5_dec_bi_hw_segments(struct bio *bio)
+{
+        unsigned short val = raid5_bi_hw_segments(bio);
+
+        --val;
+        bio->bi_phys_segments = (val << 8) | raid5_bi_phys_segments(bio);
+        return val;
+}
+
+static inline void raid5_set_bi_hw_segments(struct bio *bio, unsigned int cnt)
+{
+        bio->bi_phys_segments = raid5_bi_phys_segments(bio) || (cnt << 8);
+}
+
 static inline int raid6_next_disk(int disk, int raid_disks)
 {
         disk++;
@@ -507,7 +541,7 @@ static void ops_complete_biofill(void *stripe_head_ref)
                         while (rbi && rbi->bi_sector <
                                 dev->sector + STRIPE_SECTORS) {
                                 rbi2 = r5_next_bio(rbi, dev->sector);
-                                if (--rbi->bi_phys_segments == 0) {
+                                if (!raid5_dec_bi_phys_segments(rbi)) {
                                         rbi->bi_next = return_bi;
                                         return_bi = rbi;
                                 }
@@ -1725,7 +1759,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, in
         if (*bip)
                 bi->bi_next = *bip;
         *bip = bi;
-        bi->bi_phys_segments ++;
+        bi->bi_phys_segments++;
         spin_unlock_irq(&conf->device_lock);
         spin_unlock(&sh->lock);
 
@@ -1819,7 +1853,7 @@ handle_failed_stripe(raid5_conf_t *conf, struct stripe_head *sh,
                         sh->dev[i].sector + STRIPE_SECTORS) {
                         struct bio *nextbi = r5_next_bio(bi, sh->dev[i].sector);
                         clear_bit(BIO_UPTODATE, &bi->bi_flags);
-                        if (--bi->bi_phys_segments == 0) {
+                        if (!raid5_dec_bi_phys_segments(bi)) {
                                 md_write_end(conf->mddev);
                                 bi->bi_next = *return_bi;
                                 *return_bi = bi;
@@ -1834,7 +1868,7 @@ handle_failed_stripe(raid5_conf_t *conf, struct stripe_head *sh,
                        sh->dev[i].sector + STRIPE_SECTORS) {
                         struct bio *bi2 = r5_next_bio(bi, sh->dev[i].sector);
                         clear_bit(BIO_UPTODATE, &bi->bi_flags);
-                        if (--bi->bi_phys_segments == 0) {
+                        if (!raid5_dec_bi_phys_segments(bi)) {
                                 md_write_end(conf->mddev);
                                 bi->bi_next = *return_bi;
                                 *return_bi = bi;
@@ -1858,7 +1892,7 @@ handle_failed_stripe(raid5_conf_t *conf, struct stripe_head *sh,
                                 struct bio *nextbi =
                                         r5_next_bio(bi, sh->dev[i].sector);
                                 clear_bit(BIO_UPTODATE, &bi->bi_flags);
-                                if (--bi->bi_phys_segments == 0) {
+                                if (!raid5_dec_bi_phys_segments(bi)) {
                                         bi->bi_next = *return_bi;
                                         *return_bi = bi;
                                 }
@@ -2033,7 +2067,7 @@ static void handle_stripe_clean_event(raid5_conf_t *conf,
                                 while (wbi && wbi->bi_sector <
                                         dev->sector + STRIPE_SECTORS) {
                                         wbi2 = r5_next_bio(wbi, dev->sector);
-                                        if (--wbi->bi_phys_segments == 0) {
+                                        if (!raid5_dec_bi_phys_segments(wbi)) {
                                                 md_write_end(conf->mddev);
                                                 wbi->bi_next = *return_bi;
                                                 *return_bi = wbi;
@@ -2814,7 +2848,7 @@ static bool handle_stripe6(struct stripe_head *sh, struct page *tmp_page)
                                 copy_data(0, rbi, dev->page, dev->sector);
                                 rbi2 = r5_next_bio(rbi, dev->sector);
                                 spin_lock_irq(&conf->device_lock);
-                                if (--rbi->bi_phys_segments == 0) {
+                                if (!raid5_dec_bi_phys_segments(rbi)) {
                                         rbi->bi_next = return_bi;
                                         return_bi = rbi;
                                 }
@@ -3155,8 +3189,11 @@ static struct bio *remove_bio_from_retry(raid5_conf_t *conf)
         if(bi) {
                 conf->retry_read_aligned_list = bi->bi_next;
                 bi->bi_next = NULL;
+                /*
+                 * this sets the active strip count to 1 and the processed
+                 * strip count to zero (upper 8 bits)
+                 */
                 bi->bi_phys_segments = 1; /* biased count of active stripes */
-                bi->bi_hw_segments = 0; /* count of processed stripes */
         }
 
         return bi;
@@ -3206,8 +3243,7 @@ static int bio_fits_rdev(struct bio *bi)
         if ((bi->bi_size>>9) > q->max_sectors)
                 return 0;
         blk_recount_segments(q, bi);
-        if (bi->bi_phys_segments > q->max_phys_segments ||
-            bi->bi_hw_segments > q->max_hw_segments)
+        if (bi->bi_phys_segments > q->max_phys_segments)
                 return 0;
 
         if (q->merge_bvec_fn)
@@ -3468,7 +3504,7 @@ static int make_request(struct request_queue *q, struct bio * bi)
                         
         }
         spin_lock_irq(&conf->device_lock);
-        remaining = --bi->bi_phys_segments;
+        remaining = raid5_dec_bi_phys_segments(bi);
         spin_unlock_irq(&conf->device_lock);
         if (remaining == 0) {
 
@@ -3752,7 +3788,7 @@ static int  retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio)
                      sector += STRIPE_SECTORS,
                      scnt++) {
 
-                if (scnt < raid_bio->bi_hw_segments)
+                if (scnt < raid5_bi_hw_segments(raid_bio))
                         /* already done this stripe */
                         continue;
 
@@ -3760,7 +3796,7 @@ static int  retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio)
 
                 if (!sh) {
                         /* failed to get a stripe - must wait */
-                        raid_bio->bi_hw_segments = scnt;
+                        raid5_set_bi_hw_segments(raid_bio, scnt);
                         conf->retry_read_aligned = raid_bio;
                         return handled;
                 }
@@ -3768,7 +3804,7 @@ static int  retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio)
                 set_bit(R5_ReadError, &sh->dev[dd_idx].flags);
                 if (!add_stripe_bio(sh, raid_bio, dd_idx, 0)) {
                         release_stripe(sh);
-                        raid_bio->bi_hw_segments = scnt;
+                        raid5_set_bi_hw_segments(raid_bio, scnt);
                         conf->retry_read_aligned = raid_bio;
                         return handled;
                 }
@@ -3778,7 +3814,7 @@ static int  retry_aligned_read(raid5_conf_t *conf, struct bio *raid_bio)
                 handled++;
         }
         spin_lock_irq(&conf->device_lock);
-        remaining = --raid_bio->bi_phys_segments;
+        remaining = raid5_dec_bi_phys_segments(raid_bio);
         spin_unlock_irq(&conf->device_lock);
         if (remaining == 0)
                 bio_endio(raid_bio, 0);