btrfs: use integrated bitmaps for btrfs_raid_bio::dbitmap and finish_pbitmap

Previsouly we use "unsigned long *" for those two bitmaps.

But since we only support fixed stripe length (64KiB, already checked in
tree-checker), "unsigned long *" is really a waste of memory, while we
can just use "unsigned long".

This saves us 8 bytes in total for btrfs_raid_bio.

To be extra safe, add an ASSERT() making sure calculated
@stripe_nsectors is always smaller than BITS_PER_LONG.

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 e03a38a..90f6ae4 100644 (file)
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -164,6 +164,13 @@ struct btrfs_raid_bio {
        atomic_t stripes_pending;
 
        atomic_t error;
+
+       /* Bitmap to record which horizontal stripe has data */
+       unsigned long dbitmap;
+
+       /* Allocated with stripe_nsectors-many bits for finish_*() calls */
+       unsigned long finish_pbitmap;
+
        /*
         * these are two arrays of pointers.  We allocate the
         * rbio big enough to hold them both and setup their
@@ -184,14 +191,8 @@ struct btrfs_raid_bio {
         */
        struct sector_ptr *stripe_sectors;
 
-       /* Bitmap to record which horizontal stripe has data */
-       unsigned long *dbitmap;
-
        /* allocated with real_stripes-many pointers for finish_*() calls */
        void **finish_pointers;
-
-       /* Allocated with stripe_nsectors-many bits for finish_*() calls */
-       unsigned long *finish_pbitmap;
 };
 
 static int __raid56_parity_recover(struct btrfs_raid_bio *rbio);
@@ -1038,14 +1039,17 @@ static struct btrfs_raid_bio *alloc_rbio(struct btrfs_fs_info *fs_info,
        ASSERT(IS_ALIGNED(stripe_len, PAGE_SIZE));
        /* PAGE_SIZE must also be aligned to sectorsize for subpage support */
        ASSERT(IS_ALIGNED(PAGE_SIZE, fs_info->sectorsize));
+       /*
+        * Our current stripe len should be fixed to 64k thus stripe_nsectors
+        * (at most 16) should be no larger than BITS_PER_LONG.
+        */
+       ASSERT(stripe_nsectors <= BITS_PER_LONG);
 
        rbio = kzalloc(sizeof(*rbio) +
                       sizeof(*rbio->stripe_pages) * num_pages +
                       sizeof(*rbio->bio_sectors) * num_sectors +
                       sizeof(*rbio->stripe_sectors) * num_sectors +
-                      sizeof(*rbio->finish_pointers) * real_stripes +
-                      sizeof(*rbio->dbitmap) * BITS_TO_LONGS(stripe_nsectors) +
-                      sizeof(*rbio->finish_pbitmap) * BITS_TO_LONGS(stripe_nsectors),
+                      sizeof(*rbio->finish_pointers) * real_stripes,
                       GFP_NOFS);
        if (!rbio)
                return ERR_PTR(-ENOMEM);
@@ -1081,8 +1085,6 @@ static struct btrfs_raid_bio *alloc_rbio(struct btrfs_fs_info *fs_info,
        CONSUME_ALLOC(rbio->bio_sectors, num_sectors);
        CONSUME_ALLOC(rbio->stripe_sectors, num_sectors);
        CONSUME_ALLOC(rbio->finish_pointers, real_stripes);
-       CONSUME_ALLOC(rbio->dbitmap, BITS_TO_LONGS(stripe_nsectors));
-       CONSUME_ALLOC(rbio->finish_pbitmap, BITS_TO_LONGS(stripe_nsectors));
 #undef  CONSUME_ALLOC
 
        if (bioc->map_type & BTRFS_BLOCK_GROUP_RAID5)
@@ -1939,7 +1941,7 @@ static void __raid_recover_end_io(struct btrfs_raid_bio *rbio)
                 * which we have data when doing parity scrub.
                 */
                if (rbio->operation == BTRFS_RBIO_PARITY_SCRUB &&
-                   !test_bit(sectornr, rbio->dbitmap))
+                   !test_bit(sectornr, &rbio->dbitmap))
                        continue;
 
                /*
@@ -2374,7 +2376,7 @@ struct btrfs_raid_bio *raid56_parity_alloc_scrub_rbio(struct bio *bio,
        }
        ASSERT(i < rbio->real_stripes);
 
-       bitmap_copy(rbio->dbitmap, dbitmap, stripe_nsectors);
+       bitmap_copy(&rbio->dbitmap, dbitmap, stripe_nsectors);
 
        /*
         * We have already increased bio_counter when getting bioc, record it
@@ -2412,7 +2414,7 @@ static int alloc_rbio_essential_pages(struct btrfs_raid_bio *rbio)
        int stripe;
        int sectornr;
 
-       for_each_set_bit(sectornr, rbio->dbitmap, rbio->stripe_nsectors) {
+       for_each_set_bit(sectornr, &rbio->dbitmap, rbio->stripe_nsectors) {
                for (stripe = 0; stripe < rbio->real_stripes; stripe++) {
                        struct page *page;
                        int index = (stripe * rbio->stripe_nsectors + sectornr) *
@@ -2437,7 +2439,7 @@ static noinline void finish_parity_scrub(struct btrfs_raid_bio *rbio,
        struct btrfs_io_context *bioc = rbio->bioc;
        const u32 sectorsize = bioc->fs_info->sectorsize;
        void **pointers = rbio->finish_pointers;
-       unsigned long *pbitmap = rbio->finish_pbitmap;
+       unsigned long *pbitmap = &rbio->finish_pbitmap;
        int nr_data = rbio->nr_data;
        int stripe;
        int sectornr;
@@ -2460,7 +2462,7 @@ static noinline void finish_parity_scrub(struct btrfs_raid_bio *rbio,
 
        if (bioc->num_tgtdevs && bioc->tgtdev_map[rbio->scrubp]) {
                is_replace = 1;
-               bitmap_copy(pbitmap, rbio->dbitmap, rbio->stripe_nsectors);
+               bitmap_copy(pbitmap, &rbio->dbitmap, rbio->stripe_nsectors);
        }
 
        /*
@@ -2497,7 +2499,7 @@ static noinline void finish_parity_scrub(struct btrfs_raid_bio *rbio,
        /* Map the parity stripe just once */
        pointers[nr_data] = kmap_local_page(p_sector.page);
 
-       for_each_set_bit(sectornr, rbio->dbitmap, rbio->stripe_nsectors) {
+       for_each_set_bit(sectornr, &rbio->dbitmap, rbio->stripe_nsectors) {
                struct sector_ptr *sector;
                void *parity;
 
@@ -2525,7 +2527,7 @@ static noinline void finish_parity_scrub(struct btrfs_raid_bio *rbio,
                        memcpy(parity, pointers[rbio->scrubp], sectorsize);
                else
                        /* Parity is right, needn't writeback */
-                       bitmap_clear(rbio->dbitmap, sectornr, 1);
+                       bitmap_clear(&rbio->dbitmap, sectornr, 1);
                kunmap_local(parity);
 
                for (stripe = nr_data - 1; stripe >= 0; stripe--)
@@ -2547,7 +2549,7 @@ writeback:
         * higher layers (the bio_list in our rbio) and our p/q.  Ignore
         * everything else.
         */
-       for_each_set_bit(sectornr, rbio->dbitmap, rbio->stripe_nsectors) {
+       for_each_set_bit(sectornr, &rbio->dbitmap, rbio->stripe_nsectors) {
                struct sector_ptr *sector;
 
                sector = rbio_stripe_sector(rbio, rbio->scrubp, sectornr);
@@ -2714,7 +2716,7 @@ static void raid56_parity_scrub_stripe(struct btrfs_raid_bio *rbio)
         * stripe
         */
        for (stripe = 0; stripe < rbio->real_stripes; stripe++) {
-               for_each_set_bit(sectornr , rbio->dbitmap, rbio->stripe_nsectors) {
+               for_each_set_bit(sectornr, &rbio->dbitmap, rbio->stripe_nsectors) {
                        struct sector_ptr *sector;
                        /*
                         * We want to find all the sectors missing from the