RepoMirrors/btrfs-progs
1
0
Fork 0
mirror of https://github.com/kdave/btrfs-progs synced 2024-12-28 09:02:19 +00:00
Code Issues Packages Projects Releases Wiki Activity

btrfs-progs: check: don't calculate csum for preallocated file extents

Browse Source 
[BUG]
If a btrfs filesystem has preallocated file extents, 'btrfs check
--init-csum-tree' will create csum item for preallocated extents, and
cause error:

  # mkfs.btrfs -f test.img
  # mount test.img /mnt/btrfs
  # fallocate -l 32K /mnt/btrfs/file
  # umount /mnt/btrfs
  # btrfs check --init-csum-tree --force test.img
  ...
  [4/7] checking fs roots
  root 5 inode 257 errors 800, odd csum item
  ERROR: errors found in fs roots
  found 376832 bytes used, error(s) found

And the csum tree is not empty, containing csum for the preallocated
extent:

  $ btrfs ins dump-tree -t csum test.img
  btrfs-progs v5.15.1
  checksum tree key (CSUM_TREE ROOT_ITEM 0)
  leaf 30408704 items 1 free space 16226 generation 9 owner CSUM_TREE
  leaf 30408704 flags 0x1(WRITTEN) backref revision 1
  fs uuid ecc79835-5611-4609-b985-e4ccd6f15b54
  chunk uuid b1c75553-5b82-4aa6-bbbe-e7f50643b1a8
  	item 0 key (EXTENT_CSUM EXTENT_CSUM 13631488) itemoff 16251 itemsize 32
  		range start 13631488 end 13664256 length 32768

[CAUSE]
For `--init-csum-tree` alone, we will use extent tree to iterate each
data extent, and calculate csum for them.

But extent items alone can not tell us if the file extent belongs to a
NODATASUM inode, nor if it's preallocated.

Thus we create csums for those data extents, and cause the problem.

[FIX]
However the fix is not that simple, we can not just generate csum for
non-preallocated range.

As the following case we still need csum for the un-referred part:

  xfs_io -f -c "pwrite 0 8K" -c "sync" -c "punch 0 4K"

So here we have to go another direction by:

- Always generate csum for the whole data extent
  This is the same as the old code

- Iterate the file extents, and delete csum for preallocated range
  or NODATASUM inodes

Issue: #430
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2022-01-14 08:51:21 +08:00 committed by David Sterba
parent f8bc08cb75
commit 9e349ff18c
1 changed files with 105 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

106
check/mode-common.c
View File

@ -22,6 +22,7 @@
#include "common/utils.h"
#include "kernel-shared/disk-io.h"
#include "kernel-shared/volumes.h"
#include "kernel-shared/backref.h"
#include "common/repair.h"
#include "check/mode-common.h"
@ -1338,6 +1339,92 @@ out:
return ret;
}
static int remove_csum_for_file_extent(u64 ino, u64 offset, u64 rootid, void *ctx)
{
struct btrfs_trans_handle *trans = (struct btrfs_trans_handle *)ctx;
struct btrfs_fs_info *fs_info = trans->fs_info;
struct btrfs_file_extent_item *fi;
struct btrfs_inode_item *ii;
struct btrfs_path path = {};
struct btrfs_key key;
struct btrfs_root *root;
bool nocsum = false;
u8 type;
u64 disk_bytenr;
u64 disk_len;
int ret = 0;
key.objectid = rootid;
key.type = BTRFS_ROOT_ITEM_KEY;
key.offset = (u64)-1;
root = btrfs_read_fs_root(fs_info, &key);
if (IS_ERR(root)) {
ret = PTR_ERR(root);
goto out;
}
/* Check if the inode has NODATASUM flag */
key.objectid = ino;
key.type = BTRFS_INODE_ITEM_KEY;
key.offset = 0;
ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
if (ret > 0)
ret = -ENOENT;
if (ret < 0)
goto out;
ii = btrfs_item_ptr(path.nodes[0], path.slots[0],
struct btrfs_inode_item);
if (btrfs_inode_flags(path.nodes[0], ii) & BTRFS_INODE_NODATASUM)
nocsum = true;
btrfs_release_path(&path);
/* Check the file extent item and delete csum if needed */
key.objectid = ino;
key.type = BTRFS_EXTENT_DATA_KEY;
key.offset = offset;
ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
if (ret > 0)
ret = -ENOENT;
if (ret < 0)
goto out;
fi = btrfs_item_ptr(path.nodes[0], path.slots[0],
struct btrfs_file_extent_item);
type = btrfs_file_extent_type(path.nodes[0], fi);
if (btrfs_file_extent_disk_bytenr(path.nodes[0], fi) == 0)
goto out;
/* Compressed extent should have csum, skip it */
if (btrfs_file_extent_compression(path.nodes[0], fi) !=
BTRFS_COMPRESS_NONE)
goto out;
/*
* We only want to delete the csum range if the inode has NODATASUM
* flag or it's a preallocated extent.
*/
if (!(nocsum || type == BTRFS_FILE_EXTENT_PREALLOC))
goto out;
/* If NODATASUM, we need to remove all csum for the extent */
if (nocsum) {
disk_bytenr = btrfs_file_extent_disk_bytenr(path.nodes[0], fi);
disk_len = btrfs_file_extent_disk_num_bytes(path.nodes[0], fi);
} else {
disk_bytenr = btrfs_file_extent_disk_bytenr(path.nodes[0], fi) +
btrfs_file_extent_offset(path.nodes[0], fi);
disk_len = btrfs_file_extent_num_bytes(path.nodes[0], fi);
}
btrfs_release_path(&path);
/* Now delete the csum for the preallocated or nodatasum range */
ret = btrfs_del_csums(trans, disk_bytenr, disk_len);
out:
btrfs_release_path(&path);
return ret;
}
static int fill_csum_tree_from_extent(struct btrfs_trans_handle *trans,
struct btrfs_root *extent_root)
{
@ -1390,10 +1477,27 @@ static int fill_csum_tree_from_extent(struct btrfs_trans_handle *trans,
path.slots[0]++;
continue;
}
/*
* Generate the datasum unconditionally first.
*
* This will generate csum for preallocated extents, but that
* will be later deleted.
*
* This is to address cases like this:
* fallocate 0 8K
* pwrite 0 4k
* sync
* punch 0 4k
*
* Above case we will have csum for [0, 4K) and that's valid.
*/
csum_root = btrfs_csum_root(gfs_info, key.objectid);
ret = populate_csum(trans, csum_root, buf, key.objectid,
key.offset);
if (ret < 0)
break;
ret = iterate_extent_inodes(trans->fs_info, key.objectid, 0, 0,
remove_csum_for_file_extent, trans);
if (ret)
break;
path.slots[0]++;