btrfs: remove redundant csum buffer in btrfs_io_bio

The io_bio tracks checksums and has an inline buffer or an allocated
one. And there's a third member that points to the right one, but we
don't need to use an extra pointer for that. Let btrfs_io_bio::csum
point to the right buffer and check that the inline buffer is not
accidentally freed.

This shrinks struct btrfs_io_bio by 8 bytes.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index ba74827..1f2d0a6 100644 (file)
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -144,7 +144,10 @@ int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
 
 static void btrfs_io_bio_endio_readpage(struct btrfs_io_bio *bio, int err)
 {
-       kfree(bio->csum_allocated);
+       if (bio->csum != bio->csum_inline) {
+               kfree(bio->csum);
+               bio->csum = NULL;
+       }
 }
 
 static blk_status_t __btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
@@ -175,13 +178,12 @@ static blk_status_t __btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio
        nblocks = bio->bi_iter.bi_size >> inode->i_sb->s_blocksize_bits;
        if (!dst) {
                if (nblocks * csum_size > BTRFS_BIO_INLINE_CSUM_SIZE) {
-                       btrfs_bio->csum_allocated = kmalloc_array(nblocks,
-                                       csum_size, GFP_NOFS);
-                       if (!btrfs_bio->csum_allocated) {
+                       btrfs_bio->csum = kmalloc_array(nblocks, csum_size,
+                                                       GFP_NOFS);
+                       if (!btrfs_bio->csum) {
                                btrfs_free_path(path);
                                return BLK_STS_RESOURCE;
                        }
-                       btrfs_bio->csum = btrfs_bio->csum_allocated;
                        btrfs_bio->end_io = btrfs_io_bio_endio_readpage;
                } else {
                        btrfs_bio->csum = btrfs_bio->csum_inline;

diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 8b092bb..702c78c 100644 (file)
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -274,7 +274,6 @@ struct btrfs_io_bio {
        u64 logical;
        u8 *csum;
        u8 csum_inline[BTRFS_BIO_INLINE_CSUM_SIZE];
-       u8 *csum_allocated;
        btrfs_io_bio_end_io_t *end_io;
        struct bvec_iter iter;
        /*