From: Robbie Ko <robbi...@synology.com>
[BUG]
Range clone can cause fiemap to return error result.
Like:
# mount /dev/vdb5 /mnt/btrfs
# dd if=/dev/zero bs=16K count=2 oflag=dsync of=/mnt/btrfs/file
# xfs_io -c "fiemap -v" /mnt/btrfs/file
/mnt/btrfs/file:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..63]: 4241424..4241487 64 0x1
# cloner -s $((16*1024)) /mnt/btrfs/file /mnt/btrfs/file_clone
# xfs_io -c "fiemap -v" /mnt/btrfs/file
/mnt/btrfs/file:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..63]: 4241424..4241487 64 0x1
If we clone second file extent, we will get error FLAGS,
SHARED bit is not set.
[REASON]
Btrfs only checks if the first extent in extent map is shared,
but extent may merge.
[FIX]
Here we will check each extent with extent map range,
if one of them is shared, extent map is shared.
[PATCH RESULT]
# xfs_io -c "fiemap -v" /mnt/btrfs/file
/mnt/btrfs/file:
EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS
0: [0..63]: 4241424..4241487 64 0x2001
Signed-off-by: Robbie Ko <robbi...@synology.com>
---
fs/btrfs/extent_io.c | 146
+++++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 131 insertions(+), 15 deletions(-)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 066b6df..5c6dca9 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4394,8 +4394,8 @@ static int emit_fiemap_extent(struct
fiemap_extent_info *fieinfo,
*/
if (cache->offset + cache->len == offset &&
cache->phys + cache->len == phys &&
- (cache->flags & ~FIEMAP_EXTENT_LAST) ==
- (flags & ~FIEMAP_EXTENT_LAST)) {
+ (cache->flags & ~(FIEMAP_EXTENT_LAST|FIEMAP_EXTENT_SHARED)) ==
+ (flags & ~(FIEMAP_EXTENT_LAST|FIEMAP_EXTENT_SHARED))) {
cache->len += len;
cache->flags |= flags;
goto try_submit_last;
@@ -4450,6 +4450,134 @@ static int emit_last_fiemap_cache(struct
btrfs_fs_info *fs_info,
return ret;
}
+/*
+ * Helper to check the file range is shared.
+ *
+ * Fiemap extent will be combined with many extents, so we need to
examine
+ * each extent, and if shared, the results are shared.
+ *
+ * Return: 0 if file range is not shared, 1 if it is shared, < 0 on
error.
+ */
+static int extent_map_check_shared(struct inode *inode, u64 start,
u64 end)
+{
+ struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
+ struct btrfs_root *root = BTRFS_I(inode)->root;
+ int ret = 0;
+ struct extent_buffer *leaf;
+ struct btrfs_path *path;
+ struct btrfs_file_extent_item *fi;
+ struct btrfs_key found_key;
+ int check_prev = 1;
+ int extent_type;
+ int shared = 0;
+ u64 cur_offset;
+ u64 extent_end;
+ u64 ino = btrfs_ino(BTRFS_I(inode));
+ u64 disk_bytenr;
+
+ path = btrfs_alloc_path();
+ if (!path) {
+ return -ENOMEM;
+ }
+
+ cur_offset = start;
+ while (1) {
+ ret = btrfs_lookup_file_extent(NULL, root, path, ino,
+ cur_offset, 0);
+ if (ret < 0)
+ goto error;
+ if (ret > 0 && path->slots[0] > 0 && check_prev) {
+ leaf = path->nodes[0];
+ btrfs_item_key_to_cpu(leaf, &found_key,
+ path->slots[0] - 1);
+ if (found_key.objectid == ino &&
+ found_key.type == BTRFS_EXTENT_DATA_KEY)
+ path->slots[0]--;
+ }
+ check_prev = 0;
+next_slot:
+ leaf = path->nodes[0];
+ if (path->slots[0] >= btrfs_header_nritems(leaf)) {
+ ret = btrfs_next_leaf(root, path);
+ if (ret < 0)
+ goto error;
+ if (ret > 0)
+ break;
+ leaf = path->nodes[0];
+ }
+
+ disk_bytenr = 0;
+ btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+
+ if (found_key.objectid > ino)
+ break;
+ if (WARN_ON_ONCE(found_key.objectid < ino) ||
+ found_key.type < BTRFS_EXTENT_DATA_KEY) {
+ path->slots[0]++;
+ goto next_slot;
+ }
+ if (found_key.type > BTRFS_EXTENT_DATA_KEY ||
+ found_key.offset > end)
+ break;
+
+ fi = btrfs_item_ptr(leaf, path->slots[0],
+ struct btrfs_file_extent_item);
+ extent_type = btrfs_file_extent_type(leaf, fi);
+
+ if (extent_type == BTRFS_FILE_EXTENT_REG ||
+ extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
+ disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
+ extent_end = found_key.offset +
+ btrfs_file_extent_num_bytes(leaf, fi);
+ if (extent_end <= start) {
+ path->slots[0]++;
+ goto next_slot;
+ }
+ if (disk_bytenr == 0) {
+ path->slots[0]++;
+ goto next_slot;
+ }
+
+ btrfs_release_path(path);
+
+ /*
+ * As btrfs supports shared space, this information
+ * can be exported to userspace tools via
+ * flag FIEMAP_EXTENT_SHARED. If fi_extents_max == 0
+ * then we're just getting a count and we can skip the
+ * lookup stuff.
+ */
+ ret = btrfs_check_shared(root,
+ ino, disk_bytenr);
+ if (ret < 0)
+ goto error;
+ if (ret)
+ shared = 1;
+ ret = 0;
+ if (shared) {
+ break;
+ }
+ } else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
+ extent_end = found_key.offset +
+ btrfs_file_extent_inline_len(leaf,
+ path->slots[0], fi);
+ extent_end = ALIGN(extent_end, fs_info->sectorsize);
+ path->slots[0]++;
+ goto next_slot;
+ } else {
+ BUG_ON(1);
+ }
+ cur_offset = extent_end;
+ if (cur_offset > end)
+ break;
+ }
+
+ ret = 0;
+error:
+ btrfs_free_path(path);
+ return !ret ? shared : ret;
+}
+
int extent_fiemap(struct inode *inode, struct fiemap_extent_info
*fieinfo,
__u64 start, __u64 len, get_extent_t *get_extent)
{
@@ -4587,19 +4715,7 @@ int extent_fiemap(struct inode *inode, struct
fiemap_extent_info *fieinfo,
flags |= (FIEMAP_EXTENT_DELALLOC |
FIEMAP_EXTENT_UNKNOWN);
} else if (fieinfo->fi_extents_max) {
- u64 bytenr = em->block_start -
- (em->start - em->orig_start);
-
- /*
- * As btrfs supports shared space, this information
- * can be exported to userspace tools via
- * flag FIEMAP_EXTENT_SHARED. If fi_extents_max == 0
- * then we're just getting a count and we can skip the
- * lookup stuff.
- */
- ret = btrfs_check_shared(root,
- btrfs_ino(BTRFS_I(inode)),
- bytenr);
