On Thu, Mar 15, 2018 at 9:04 AM, Nikolay Borisov <nbori...@suse.com> wrote:
>
>
> On 14.03.2018 00:48, fdman...@kernel.org wrote:
>> From: Filipe Manana <fdman...@suse.com>
>>
>> Under some cases the filesystem checker reports an error when it finds
>> checksum items for an extent that is referenced by an inode as a prealloc
>> extent. Such cases are not an error when the extent is actually shared
>> (was cloned/reflinked) with other inodes and was written through one of
>> those other inodes.
>>
>> Example:
>>
>> $ mkfs.btrfs -f /dev/sdb
>> $ mount /dev/sdb /mnt
>>
>> $ touch /mnt/foo
>> $ xfs_io -c "falloc 0 256K" /mnt/foo
>> $ sync
>>
>> $ xfs_io -c "pwrite -S 0xab 0 256K" /mnt/foo
>> $ touch /mnt/bar
>> $ xfs_io -c "reflink /mnt/foo 0 0 256K" /mnt/bar
>> $ xfs_io -c "fsync" /mnt/bar
>>
>> <power fail>
>> $ mount /dev/sdb /mnt
>> $ umount /mnt
>>
>> $ btrfs check /dev/sdc
>> Checking filesystem on /dev/sdb
>> UUID: 52d3006e-ee3b-40eb-aa21-e56253a03d39
>> checking extents
>> checking free space cache
>> checking fs roots
>> root 5 inode 257 errors 800, odd csum item
>> ERROR: errors found in fs roots
>> found 688128 bytes used, error(s) found
>> total csum bytes: 256
>> total tree bytes: 163840
>> total fs tree bytes: 65536
>> total extent tree bytes: 16384
>> btree space waste bytes: 138819
>> file data blocks allocated: 10747904
>> referenced 10747904
>> $ echo $?
>> 1
>>
>> So teach check to not report such cases as errors by checking if the
>> extent is shared with other inodes and if so, consider it an error the
>> existence of checksum items only if all those other inodes are referencing
>> the extent as a prealloc extent.
>> This case can be hit often when running the generic/475 testcase from
>> fstests.
>>
>> A test case will follow in a separate patch.
>>
>> Signed-off-by: Filipe Manana <fdman...@suse.com>
>> ---
>>
>> V2: Made stuff work with lowmem mode as well.
>> Added a comment about the limitations of the current check.
>> Removed filtering by inode number since it was unreliable as we can
>> have different inodes with same inode number but in different roots
>> (so opted to drop the filtering instead of filtering by root as well,
>> to keep it simpler).
>>
>> check/main.c | 11 ++-
>> check/mode-common.c | 258
>> ++++++++++++++++++++++++++++++++++++++++++++++++++++
>> check/mode-common.h | 3 +
>> check/mode-lowmem.c | 14 ++-
>> 4 files changed, 281 insertions(+), 5 deletions(-)
>>
>> diff --git a/check/main.c b/check/main.c
>> index 392195ca..88e6c1e9 100644
>> --- a/check/main.c
>> +++ b/check/main.c
>> @@ -1515,8 +1515,15 @@ static int process_file_extent(struct btrfs_root
>> *root,
>> if (found < num_bytes)
>> rec->some_csum_missing = 1;
>> } else if (extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
>> - if (found > 0)
>> - rec->errors |= I_ERR_ODD_CSUM_ITEM;
>> + if (found > 0) {
>> + ret =
>> check_prealloc_extent_written(root->fs_info,
>> +
>> disk_bytenr,
>> + num_bytes);
>> + if (ret < 0)
>> + return ret;
>> + if (ret == 0)
>> + rec->errors |= I_ERR_ODD_CSUM_ITEM;
>> + }
>> }
>> }
>> return 0;
>> diff --git a/check/mode-common.c b/check/mode-common.c
>> index 1b56a968..559cd11d 100644
>> --- a/check/mode-common.c
>> +++ b/check/mode-common.c
>> @@ -24,6 +24,264 @@
>> #include "check/mode-common.h"
>>
>> /*
>> + * Check if the inode referenced by the given data reference uses the extent
>> + * at disk_bytenr as a non-prealloc extent.
>> + *
>> + * Returns 1 if true, 0 if false and < 0 on error.
>> + */
>> +static int check_prealloc_data_ref(struct btrfs_fs_info *fs_info,
>> + u64 disk_bytenr,
>> + struct btrfs_extent_data_ref *dref,
>> + struct extent_buffer *eb)
>> +{
>> + u64 rootid = btrfs_extent_data_ref_root(eb, dref);
>> + u64 objectid = btrfs_extent_data_ref_objectid(eb, dref);
>> + u64 offset = btrfs_extent_data_ref_offset(eb, dref);
>> + struct btrfs_root *root;
>> + struct btrfs_key key;
>> + struct btrfs_path path;
>> + int ret;
>> +
>> + btrfs_init_path(&path);
>> + 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;
>> + }
>> +
>> + key.objectid = objectid;
>> + key.type = BTRFS_EXTENT_DATA_KEY;
>> + key.offset = offset;
>> + ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
>> + if (ret > 0) {
>> + fprintf(stderr,
>> + "Missing file extent item for inode %llu, root %llu,
>> offset %llu",
>> + objectid, rootid, offset);
>> + ret = -ENOENT;
>> + }
>> + if (ret < 0)
>> + goto out;
>> +
>> + while (true) {
>> + struct btrfs_file_extent_item *fi;
>> + int extent_type;
>> +
>> + if (path.slots[0] >= btrfs_header_nritems(path.nodes[0])) {
>> + ret = btrfs_next_leaf(fs_info->extent_root, &path);
>
> Shouldn't you use the read fs root rather than extent root in
> btrfs_next_leaf?
It should, copy paste error.
thanks
>
>> + if (ret < 0)
>> + goto out;
>> + if (ret > 0)
>> + break;
>> + }
>> +
>> + btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
>> + if (key.objectid != objectid ||
>> + key.type != BTRFS_EXTENT_DATA_KEY)
>> + break;
>> +
>> + fi = btrfs_item_ptr(path.nodes[0], path.slots[0],
>> + struct btrfs_file_extent_item);
>> + extent_type = btrfs_file_extent_type(path.nodes[0], fi);
>> + if (extent_type != BTRFS_FILE_EXTENT_REG &&
>> + extent_type != BTRFS_FILE_EXTENT_PREALLOC)
>> + goto next;
>> +
>> + if (btrfs_file_extent_disk_bytenr(path.nodes[0], fi) !=
>> + disk_bytenr)
>> + break;
>> +
>> + if (extent_type == BTRFS_FILE_EXTENT_REG) {
>> + ret = 1;
>> + goto out;
>> + }
>> +next:
>> + path.slots[0]++;
>> + }
>> + ret = 0;
>> + out:
>> + btrfs_release_path(&path);
>> + return ret;
>> +}
>> +
>> +/*
>> + * Check if a shared data reference points to a node that has a file extent
>> item
>> + * pointing to the extent at @disk_bytenr that is not of type prealloc.
>> + *
>> + * Returns 1 if true, 0 if false and < 0 on error.
>> + */
>> +static int check_prealloc_shared_data_ref(struct btrfs_fs_info *fs_info,
>> + u64 parent,
>> + u64 disk_bytenr)
>> +{
>> + struct extent_buffer *eb;
>> + u32 nr;
>> + int i;
>> + int ret = 0;
>> +
>> + eb = read_tree_block(fs_info, parent, 0);
>> + if (!extent_buffer_uptodate(eb)) {
>> + ret = -EIO;
>> + goto out;
>> + }
>> +
>> + nr = btrfs_header_nritems(eb);
>> + for (i = 0; i < nr; i++) {
>> + struct btrfs_key key;
>> + struct btrfs_file_extent_item *fi;
>> + int extent_type;
>> +
>> + btrfs_item_key_to_cpu(eb, &key, i);
>> + if (key.type != BTRFS_EXTENT_DATA_KEY)
>> + continue;
>> +
>> + fi = btrfs_item_ptr(eb, i, struct btrfs_file_extent_item);
>> + extent_type = btrfs_file_extent_type(eb, fi);
>> + if (extent_type != BTRFS_FILE_EXTENT_REG &&
>> + extent_type != BTRFS_FILE_EXTENT_PREALLOC)
>> + continue;
>> +
>> + if (btrfs_file_extent_disk_bytenr(eb, fi) == disk_bytenr &&
>> + extent_type == BTRFS_FILE_EXTENT_REG) {
>> + ret = 1;
>> + break;
>> + }
>> + }
>> + out:
>> + free_extent_buffer(eb);
>> + return ret;
>> +}
>> +
>> +/*
>> + * Check if a prealloc extent is shared by multiple inodes and if any inode
>> has
>> + * already written to that extent. This is to avoid emitting invalid
>> warnings
>> + * about odd csum items (a inode has an extent entirely marked as prealloc
>> + * but another inode shares it and has already written to it).
>> + *
>> + * Note: right now it does not check if the number of checksum items in the
>> + * csum tree matches the number of bytes written into the ex-prealloc
>> extent.
>> + * It's complex to deal with that because the prealloc extent might have
>> been
>> + * partially written through multiple inodes and we would have to keep
>> track of
>> + * ranges, merging them and notice ranges that fully or partially overlap,
>> to
>> + * avoid false reports of csum items missing for areas of the prealloc
>> extent
>> + * that were not written to - for example if we have a 1M prealloc extent,
>> we
>> + * can have only the first half of it written, but 2 different inodes refer
>> to
>> + * the its first half (through reflinks/cloning), so keeping a counter of
>> bytes
>> + * covered by checksum items is not enough, as the correct value would be
>> 512K
>> + * and not 1M (whence the need to track ranges).
>> + *
>> + * Returns 0 if the prealloc extent was not written yet by any inode, 1 if
>> + * at least one other inode has written to it, and < 0 on error.
>> + */
>> +int check_prealloc_extent_written(struct btrfs_fs_info *fs_info,
>> + u64 disk_bytenr,
>> + u64 num_bytes)
>> +{
>> + struct btrfs_path path;
>> + struct btrfs_key key;
>> + int ret;
>> + struct btrfs_extent_item *ei;
>> + u32 item_size;
>> + unsigned long ptr;
>> + unsigned long end;
>> +
>> + key.objectid = disk_bytenr;
>> + key.type = BTRFS_EXTENT_ITEM_KEY;
>> + key.offset = num_bytes;
>> +
>> + btrfs_init_path(&path);
>> + ret = btrfs_search_slot(NULL, fs_info->extent_root, &key, &path, 0, 0);
>> + if (ret > 0) {
>> + fprintf(stderr,
>> + "Missing extent item in extent tree for disk_bytenr
>> %llu, num_bytes %llu\n",
>> + disk_bytenr, num_bytes);
>> + ret = -ENOENT;
>> + }
>> + if (ret < 0)
>> + goto out;
>> +
>> + /* First check all inline refs. */
>> + ei = btrfs_item_ptr(path.nodes[0], path.slots[0],
>> + struct btrfs_extent_item);
>> + item_size = btrfs_item_size_nr(path.nodes[0], path.slots[0]);
>> + ptr = (unsigned long)(ei + 1);
>> + end = (unsigned long)ei + item_size;
>> + while (ptr < end) {
>> + struct btrfs_extent_inline_ref *iref;
>> + int type;
>> +
>> + iref = (struct btrfs_extent_inline_ref *)ptr;
>> + type = btrfs_extent_inline_ref_type(path.nodes[0], iref);
>> + ASSERT(type == BTRFS_EXTENT_DATA_REF_KEY ||
>> + type == BTRFS_SHARED_DATA_REF_KEY);
>> +
>> + if (type == BTRFS_EXTENT_DATA_REF_KEY) {
>> + struct btrfs_extent_data_ref *dref;
>> +
>> + dref = (struct btrfs_extent_data_ref *)(&iref->offset);
>> + ret = check_prealloc_data_ref(fs_info, disk_bytenr,
>> + dref, path.nodes[0]);
>> + if (ret != 0)
>> + goto out;
>> + } else if (type == BTRFS_SHARED_DATA_REF_KEY) {
>> + u64 parent;
>> +
>> + parent = btrfs_extent_inline_ref_offset(path.nodes[0],
>> + iref);
>> + ret = check_prealloc_shared_data_ref(fs_info,
>> + parent,
>> + disk_bytenr);
>> + if (ret != 0)
>> + goto out;
>> + }
>> +
>> + ptr += btrfs_extent_inline_ref_size(type);
>> + }
>> +
>> + /* Now check if there are any non-inlined refs. */
>> + path.slots[0]++;
>> + while (true) {
>> + if (path.slots[0] >= btrfs_header_nritems(path.nodes[0])) {
>> + ret = btrfs_next_leaf(fs_info->extent_root, &path);
>> + if (ret < 0)
>> + goto out;
>> + if (ret > 0) {
>> + ret = 0;
>> + break;
>> + }
>> + }
>> +
>> + btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
>> + if (key.objectid != disk_bytenr)
>> + break;
>> +
>> + if (key.type == BTRFS_EXTENT_DATA_REF_KEY) {
>> + struct btrfs_extent_data_ref *dref;
>> +
>> + dref = btrfs_item_ptr(path.nodes[0], path.slots[0],
>> + struct btrfs_extent_data_ref);
>> + ret = check_prealloc_data_ref(fs_info, disk_bytenr,
>> + dref, path.nodes[0]);
>> + if (ret != 0)
>> + goto out;
>> + } else if (key.type == BTRFS_SHARED_DATA_REF_KEY) {
>> + ret = check_prealloc_shared_data_ref(fs_info,
>> + key.offset,
>> + disk_bytenr);
>> + if (ret != 0)
>> + goto out;
>> + }
>> +
>> + path.slots[0]++;
>> + }
>> +out:
>> + btrfs_release_path(&path);
>> + return ret;
>> +}
>> +
>> +/*
>> * Search in csum tree to find how many bytes of range [@start, @start +
>> @len)
>> * has the corresponding csum item.
>> *
>> diff --git a/check/mode-common.h b/check/mode-common.h
>> index ffae782b..79e1b0cf 100644
>> --- a/check/mode-common.h
>> +++ b/check/mode-common.h
>> @@ -80,6 +80,9 @@ static inline int fs_root_objectid(u64 objectid)
>> return is_fstree(objectid);
>> }
>>
>> +int check_prealloc_extent_written(struct btrfs_fs_info *fs_info,
>> + u64 disk_bytenr,
>> + u64 num_bytes);
>> int count_csum_range(struct btrfs_fs_info *fs_info, u64 start,
>> u64 len, u64 *found);
>> int insert_inode_item(struct btrfs_trans_handle *trans,
>> diff --git a/check/mode-lowmem.c b/check/mode-lowmem.c
>> index 2424cdc2..02806377 100644
>> --- a/check/mode-lowmem.c
>> +++ b/check/mode-lowmem.c
>> @@ -1511,9 +1511,17 @@ static int check_file_extent(struct btrfs_root *root,
>> struct btrfs_key *fkey,
>> csum_found, search_len);
>> } else if (extent_type == BTRFS_FILE_EXTENT_PREALLOC &&
>> csum_found > 0) {
>> - err |= ODD_CSUM_ITEM;
>> - error("root %llu EXTENT_DATA[%llu %llu] prealloc shouldn't
>> have csum, but has: %llu",
>> - root->objectid, fkey->objectid, fkey->offset,
>> csum_found);
>> + ret = check_prealloc_extent_written(root->fs_info,
>> + disk_bytenr,
>> + disk_num_bytes);
>> + if (ret < 0)
>> + return ret;
>> + if (ret == 0) {
>> + err |= ODD_CSUM_ITEM;
>> + error("root %llu EXTENT_DATA[%llu %llu] prealloc
>> shouldn't have csum, but has: %llu",
>> + root->objectid, fkey->objectid, fkey->offset,
>> + csum_found);
>> + }
>> }
>>
>> /* Check EXTENT_DATA hole */
>>
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
