[PATCH v3 5/5] btrfs: remove buffer_heads form superblock mirror integrity checking

Johannes Thumshirn
2020-01-27T15:59:45Z

The integrity checking code for the superblock mirrors is the last remaining
user of buffer_heads in BTRFS, change it to using plain BIOs as well.

Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>

---
Changes to v2:
- Open-code kunmap() + put_page() (David)
- Remove __GFP_NOFAIL from allocation (Josef)
- Merge error paths (David)

Changes to v1:
- Convert from alloc_page() to find_or_create_page()
---
fs/btrfs/check-integrity.c | 58 +++++++++++++++++++++++++-------------
1 file changed, 39 insertions(+), 19 deletions(-)

diff --git a/fs/btrfs/check-integrity.c b/fs/btrfs/check-integrity.c
index 4f6db2fe482a..d6ab6d3ca413 100644
--- a/fs/btrfs/check-integrity.c
+++ b/fs/btrfs/check-integrity.c
@@ -77,7 +77,6 @@

#include <linux/sched.h>
#include <linux/slab.h>
-#include <linux/buffer_head.h>
#include <linux/mutex.h>
#include <linux/genhd.h>
#include <linux/blkdev.h>
@@ -762,29 +761,48 @@ static int btrfsic_process_superblock_dev_mirror(
struct btrfs_fs_info *fs_info = state->fs_info;
struct btrfs_super_block *super_tmp;
u64 dev_bytenr;
- struct buffer_head *bh;
struct btrfsic_block *superblock_tmp;
int pass;
struct block_device *const superblock_bdev = device->bdev;
+ struct page *page;
+ struct bio bio;
+ struct bio_vec bio_vec;
+ struct address_space *mapping = superblock_bdev->bd_inode->i_mapping;
+ gfp_t gfp_mask;
+ int ret;

/* super block bytenr is always the unmapped device bytenr */
dev_bytenr = btrfs_sb_offset(superblock_mirror_num);
if (dev_bytenr + BTRFS_SUPER_INFO_SIZE > device->commit_total_bytes)
return -1;
- bh = __bread(superblock_bdev, dev_bytenr / BTRFS_BDEV_BLOCKSIZE,
- BTRFS_SUPER_INFO_SIZE);
- if (NULL == bh)
+
+ gfp_mask = mapping_gfp_constraint(mapping, ~__GFP_FS);
+
+ page = find_or_create_page(mapping, dev_bytenr >> PAGE_SHIFT, gfp_mask);
+ if (!page)
+ return -1;
+
+ bio_init(&bio, &bio_vec, 1);
+ bio.bi_iter.bi_sector = dev_bytenr >> SECTOR_SHIFT;
+ bio_set_dev(&bio, superblock_bdev);
+ bio_set_op_attrs(&bio, REQ_OP_READ, 0);
+ bio_add_page(&bio, page, BTRFS_SUPER_INFO_SIZE, 0);
+
+ ret = submit_bio_wait(&bio);
+ if (ret)
return -1;
- super_tmp = (struct btrfs_super_block *)
- (bh->b_data + (dev_bytenr & (BTRFS_BDEV_BLOCKSIZE - 1)));
+
+ unlock_page(page);
+
+ super_tmp = kmap(page);

if (btrfs_super_bytenr(super_tmp) != dev_bytenr ||
btrfs_super_magic(super_tmp) != BTRFS_MAGIC ||
memcmp(device->uuid, super_tmp->dev_item.uuid, BTRFS_UUID_SIZE) ||
btrfs_super_nodesize(super_tmp) != state->metablock_size ||
btrfs_super_sectorsize(super_tmp) != state->datablock_size) {
- brelse(bh);
- return 0;
+ ret = 0;
+ goto out_unmap;
}

superblock_tmp =
@@ -795,8 +813,8 @@ static int btrfsic_process_superblock_dev_mirror(
superblock_tmp = btrfsic_block_alloc();
if (NULL == superblock_tmp) {
pr_info("btrfsic: error, kmalloc failed!\n");
- brelse(bh);
- return -1;
+ ret = -1;
+ goto out_unmap;
}
/* for superblock, only the dev_bytenr makes sense */
superblock_tmp->dev_bytenr = dev_bytenr;
@@ -880,8 +898,8 @@ static int btrfsic_process_superblock_dev_mirror(
mirror_num)) {
pr_info("btrfsic: btrfsic_map_block(bytenr @%llu, mirror %d) failed!\n",
next_bytenr, mirror_num);
- brelse(bh);
- return -1;
+ ret = -1;
+ goto out_unmap;
}

next_block = btrfsic_block_lookup_or_add(
@@ -890,8 +908,8 @@ static int btrfsic_process_superblock_dev_mirror(
mirror_num, NULL);
if (NULL == next_block) {
btrfsic_release_block_ctx(&tmp_next_block_ctx);
- brelse(bh);
- return -1;
+ ret = -1;
+ goto out_unmap;
}

next_block->disk_key = tmp_disk_key;
@@ -902,16 +920,18 @@ static int btrfsic_process_superblock_dev_mirror(
BTRFSIC_GENERATION_UNKNOWN);
btrfsic_release_block_ctx(&tmp_next_block_ctx);
if (NULL == l) {
- brelse(bh);
- return -1;
+ ret = -1;
+ goto out_unmap;
}
}
}
if (state->print_mask & BTRFSIC_PRINT_MASK_INITIAL_ALL_TREES)
btrfsic_dump_tree_sub(state, superblock_tmp, 0);

- brelse(bh);
- return 0;
+out_unmap:
+ kunmap(page);
+ put_page(page);
+ return ret;
}

static struct btrfsic_stack_frame *btrfsic_stack_frame_alloc(void)
--
2.24.1