btrfs: raid56: extract the pq generation code into a helper

Currently finish_rmw() will update the P/Q stripes before submitting
the writes.

It's done behind a for(;;) loop, it's a little congested indent-wise, so
extract the code into a helper called generate_pq_vertical().

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index 34d51d2ef7469d23afcb268574cca2818b6cc115..66dd4e9752a97411e24e6ad947548827ea995730 100644 (file)
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -1193,6 +1193,48 @@ not_found:
        trace_info->stripe_nr = -1;
 }
 
+/* Generate PQ for one veritical stripe. */
+static void generate_pq_vertical(struct btrfs_raid_bio *rbio, int sectornr)
+{
+       void **pointers = rbio->finish_pointers;
+       const u32 sectorsize = rbio->bioc->fs_info->sectorsize;
+       struct sector_ptr *sector;
+       int stripe;
+       const bool has_qstripe = rbio->bioc->map_type & BTRFS_BLOCK_GROUP_RAID6;
+
+       /* First collect one sector from each data stripe */
+       for (stripe = 0; stripe < rbio->nr_data; stripe++) {
+               sector = sector_in_rbio(rbio, stripe, sectornr, 0);
+               pointers[stripe] = kmap_local_page(sector->page) +
+                                  sector->pgoff;
+       }
+
+       /* Then add the parity stripe */
+       sector = rbio_pstripe_sector(rbio, sectornr);
+       sector->uptodate = 1;
+       pointers[stripe++] = kmap_local_page(sector->page) + sector->pgoff;
+
+       if (has_qstripe) {
+               /*
+                * RAID6, add the qstripe and call the library function
+                * to fill in our p/q
+                */
+               sector = rbio_qstripe_sector(rbio, sectornr);
+               sector->uptodate = 1;
+               pointers[stripe++] = kmap_local_page(sector->page) +
+                                    sector->pgoff;
+
+               raid6_call.gen_syndrome(rbio->real_stripes, sectorsize,
+                                       pointers);
+       } else {
+               /* raid5 */
+               memcpy(pointers[rbio->nr_data], pointers[0], sectorsize);
+               run_xor(pointers + 1, rbio->nr_data - 1, sectorsize);
+       }
+       for (stripe = stripe - 1; stripe >= 0; stripe--)
+               kunmap_local(pointers[stripe]);
+}
+
 /*
  * this is called from one of two situations.  We either
  * have a full stripe from the higher layers, or we've read all
@@ -1204,28 +1246,17 @@ not_found:
 static noinline void finish_rmw(struct btrfs_raid_bio *rbio)
 {
        struct btrfs_io_context *bioc = rbio->bioc;
-       const u32 sectorsize = bioc->fs_info->sectorsize;
-       void **pointers = rbio->finish_pointers;
-       int nr_data = rbio->nr_data;
        /* The total sector number inside the full stripe. */
        int total_sector_nr;
        int stripe;
        /* Sector number inside a stripe. */
        int sectornr;
-       bool has_qstripe;
        struct bio_list bio_list;
        struct bio *bio;
        int ret;
 
        bio_list_init(&bio_list);
 
-       if (rbio->real_stripes - rbio->nr_data == 1)
-               has_qstripe = false;
-       else if (rbio->real_stripes - rbio->nr_data == 2)
-               has_qstripe = true;
-       else
-               BUG();
-
        /* We should have at least one data sector. */
        ASSERT(bitmap_weight(&rbio->dbitmap, rbio->stripe_nsectors));
 
@@ -1258,41 +1289,8 @@ static noinline void finish_rmw(struct btrfs_raid_bio *rbio)
        else
                clear_bit(RBIO_CACHE_READY_BIT, &rbio->flags);
 
-       for (sectornr = 0; sectornr < rbio->stripe_nsectors; sectornr++) {
-               struct sector_ptr *sector;
-
-               /* First collect one sector from each data stripe */
-               for (stripe = 0; stripe < nr_data; stripe++) {
-                       sector = sector_in_rbio(rbio, stripe, sectornr, 0);
-                       pointers[stripe] = kmap_local_page(sector->page) +
-                                          sector->pgoff;
-               }
-
-               /* Then add the parity stripe */
-               sector = rbio_pstripe_sector(rbio, sectornr);
-               sector->uptodate = 1;
-               pointers[stripe++] = kmap_local_page(sector->page) + sector->pgoff;
-
-               if (has_qstripe) {
-                       /*
-                        * RAID6, add the qstripe and call the library function
-                        * to fill in our p/q
-                        */
-                       sector = rbio_qstripe_sector(rbio, sectornr);
-                       sector->uptodate = 1;
-                       pointers[stripe++] = kmap_local_page(sector->page) +
-                                            sector->pgoff;
-
-                       raid6_call.gen_syndrome(rbio->real_stripes, sectorsize,
-                                               pointers);
-               } else {
-                       /* raid5 */
-                       memcpy(pointers[nr_data], pointers[0], sectorsize);
-                       run_xor(pointers + 1, nr_data - 1, sectorsize);
-               }
-               for (stripe = stripe - 1; stripe >= 0; stripe--)
-                       kunmap_local(pointers[stripe]);
-       }
+       for (sectornr = 0; sectornr < rbio->stripe_nsectors; sectornr++)
+               generate_pq_vertical(rbio, sectornr);
 
        /*
         * Start writing.  Make bios for everything from the higher layers (the