btrfs: use integrated bitmaps for scrub_parity::dbitmap and ebitmap

Previously 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 scrub_parity.

To be extra safe, add an ASSERT() making sure calclulated @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/scrub.c b/fs/btrfs/scrub.c
index e7b0323e6efd8cd96c6f6498188608e21c31b86c..db700e6ec5a932087ff78bcd9955c9b091b7d912 100644 (file)
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -135,15 +135,13 @@ struct scrub_parity {
        struct work_struct      work;
 
        /* Mark the parity blocks which have data */
-       unsigned long           *dbitmap;
+       unsigned long           dbitmap;
 
        /*
         * Mark the parity blocks which have data, but errors happen when
         * read data or check data
         */
-       unsigned long           *ebitmap;
-
-       unsigned long           bitmap[];
+       unsigned long           ebitmap;
 };
 
 struct scrub_ctx {
@@ -2406,13 +2404,13 @@ static inline void __scrub_mark_bitmap(struct scrub_parity *sparity,
 static inline void scrub_parity_mark_sectors_error(struct scrub_parity *sparity,
                                                   u64 start, u32 len)
 {
-       __scrub_mark_bitmap(sparity, sparity->ebitmap, start, len);
+       __scrub_mark_bitmap(sparity, &sparity->ebitmap, start, len);
 }
 
 static inline void scrub_parity_mark_sectors_data(struct scrub_parity *sparity,
                                                  u64 start, u32 len)
 {
-       __scrub_mark_bitmap(sparity, sparity->dbitmap, start, len);
+       __scrub_mark_bitmap(sparity, &sparity->dbitmap, start, len);
 }
 
 static void scrub_block_complete(struct scrub_block *sblock)
@@ -2763,7 +2761,7 @@ static void scrub_free_parity(struct scrub_parity *sparity)
        struct scrub_sector *curr, *next;
        int nbits;
 
-       nbits = bitmap_weight(sparity->ebitmap, sparity->nsectors);
+       nbits = bitmap_weight(&sparity->ebitmap, sparity->nsectors);
        if (nbits) {
                spin_lock(&sctx->stat_lock);
                sctx->stat.read_errors += nbits;
@@ -2795,8 +2793,8 @@ static void scrub_parity_bio_endio(struct bio *bio)
        struct btrfs_fs_info *fs_info = sparity->sctx->fs_info;
 
        if (bio->bi_status)
-               bitmap_or(sparity->ebitmap, sparity->ebitmap, sparity->dbitmap,
-                         sparity->nsectors);
+               bitmap_or(&sparity->ebitmap, &sparity->ebitmap,
+                         &sparity->dbitmap, sparity->nsectors);
 
        bio_put(bio);
 
@@ -2814,8 +2812,8 @@ static void scrub_parity_check_and_repair(struct scrub_parity *sparity)
        u64 length;
        int ret;
 
-       if (!bitmap_andnot(sparity->dbitmap, sparity->dbitmap, sparity->ebitmap,
-                          sparity->nsectors))
+       if (!bitmap_andnot(&sparity->dbitmap, &sparity->dbitmap,
+                          &sparity->ebitmap, sparity->nsectors))
                goto out;
 
        length = sparity->logic_end - sparity->logic_start;
@@ -2833,7 +2831,7 @@ static void scrub_parity_check_and_repair(struct scrub_parity *sparity)
 
        rbio = raid56_parity_alloc_scrub_rbio(bio, bioc, length,
                                              sparity->scrub_dev,
-                                             sparity->dbitmap,
+                                             &sparity->dbitmap,
                                              sparity->nsectors);
        if (!rbio)
                goto rbio_out;
@@ -2847,7 +2845,7 @@ rbio_out:
 bioc_out:
        btrfs_bio_counter_dec(fs_info);
        btrfs_put_bioc(bioc);
-       bitmap_or(sparity->ebitmap, sparity->ebitmap, sparity->dbitmap,
+       bitmap_or(&sparity->ebitmap, &sparity->ebitmap, &sparity->dbitmap,
                  sparity->nsectors);
        spin_lock(&sctx->stat_lock);
        sctx->stat.malloc_errors++;
@@ -2856,11 +2854,6 @@ out:
        scrub_free_parity(sparity);
 }
 
-static inline int scrub_calc_parity_bitmap_len(int nsectors)
-{
-       return DIV_ROUND_UP(nsectors, BITS_PER_LONG) * sizeof(long);
-}
-
 static void scrub_parity_get(struct scrub_parity *sparity)
 {
        refcount_inc(&sparity->refs);
@@ -3131,7 +3124,6 @@ static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
        int ret;
        struct scrub_parity *sparity;
        int nsectors;
-       int bitmap_len;
 
        path = btrfs_alloc_path();
        if (!path) {
@@ -3145,9 +3137,8 @@ static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
 
        ASSERT(map->stripe_len <= U32_MAX);
        nsectors = map->stripe_len >> fs_info->sectorsize_bits;
-       bitmap_len = scrub_calc_parity_bitmap_len(nsectors);
-       sparity = kzalloc(sizeof(struct scrub_parity) + 2 * bitmap_len,
-                         GFP_NOFS);
+       ASSERT(nsectors <= BITS_PER_LONG);
+       sparity = kzalloc(sizeof(struct scrub_parity), GFP_NOFS);
        if (!sparity) {
                spin_lock(&sctx->stat_lock);
                sctx->stat.malloc_errors++;
@@ -3165,8 +3156,6 @@ static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
        sparity->logic_end = logic_end;
        refcount_set(&sparity->refs, 1);
        INIT_LIST_HEAD(&sparity->sectors_list);
-       sparity->dbitmap = sparity->bitmap;
-       sparity->ebitmap = (void *)sparity->bitmap + bitmap_len;
 
        ret = 0;
        for (cur_logical = logic_start; cur_logical < logic_end;