[PATCH v4 2/3] Btrfs: simplify inline extent handling when doing reflinks

fdmanana
2020-02-28T13:04:27Z

We can not reflink parts of an inline extent, we must always reflink the
whole inline extent. We know that inline extents always start at file
offset 0 and that can never represent an amount of data larger then the
filesystem's sector size (both compressed and uncompressed). We also have
had the constraints that reflink operations must have a start offset that
is aligned to the sector size and an end offset that is also aligned or
it ends the inode's i_size, so there's no way for user space to be able
to do a reflink operation that will refer to only a part of an inline
extent.

Initially there was a bug in the inlining code that could allow compressed
inline extents that encoded more than 1 page, but that was fixed in 2008
by commit 70b99e6959a4c2 ("Btrfs: Compression corner fixes") since that
was problematic.

So remove all the extent cloning code that deals with the possibility
of cloning only partial inline extents.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
---

V4: No changes.
V3: No changes.
V2: No changes.

fs/btrfs/reflink.c | 53 ++++++++++++++---------------------------------------
1 file changed, 14 insertions(+), 39 deletions(-)

diff --git a/fs/btrfs/reflink.c b/fs/btrfs/reflink.c
index deecb1580e8e..6498ad3c2d02 100644
--- a/fs/btrfs/reflink.c
+++ b/fs/btrfs/reflink.c
@@ -74,9 +74,8 @@ static int clone_copy_inline_extent(struct inode *dst,
struct btrfs_key *new_key,
const u64 drop_start,
const u64 datal,
- const u64 skip,
const u64 size,
- char *inline_data)
+ const char *inline_data)
{
struct btrfs_fs_info *fs_info = btrfs_sb(dst->i_sb);
struct btrfs_root *root = BTRFS_I(dst)->root;
@@ -172,12 +171,6 @@ static int clone_copy_inline_extent(struct inode *dst,
if (ret)
return ret;

- if (skip) {
- const u32 start = btrfs_file_extent_calc_inline_size(0);
-
- memmove(inline_data + start, inline_data + start + skip, datal);
- }
-
write_extent_buffer(path->nodes[0], inline_data,
btrfs_item_ptr_offset(path->nodes[0],
path->slots[0]),
@@ -241,7 +234,6 @@ static int btrfs_clone(struct inode *src, struct inode *inode,
struct btrfs_key new_key;
u64 disko = 0, diskl = 0;
u64 datao = 0, datal = 0;
- u8 comp;
u64 drop_start;

/*
@@ -287,7 +279,6 @@ static int btrfs_clone(struct inode *src, struct inode *inode,

extent = btrfs_item_ptr(leaf, slot,
struct btrfs_file_extent_item);
- comp = btrfs_file_extent_compression(leaf, extent);
type = btrfs_file_extent_type(leaf, extent);
if (type == BTRFS_FILE_EXTENT_REG ||
type == BTRFS_FILE_EXTENT_PREALLOC) {
@@ -370,23 +361,18 @@ static int btrfs_clone(struct inode *src, struct inode *inode,
if (ret)
goto out;
} else if (type == BTRFS_FILE_EXTENT_INLINE) {
- u64 skip = 0;
- u64 trim = 0;
-
- if (off > key.offset) {
- skip = off - key.offset;
- new_key.offset += skip;
- }
-
- if (key.offset + datal > off + len)
- trim = key.offset + datal - (off + len);
-
- if (comp && (skip || trim)) {
- ret = -EINVAL;
- goto out;
- }
- size -= skip + trim;
- datal -= skip + trim;
+ /*
+ * Inline extents always have to start at file offset 0
+ * and can never be bigger then the sector size. We can
+ * never clone only parts of an inline extent, since all
+ * reflink operations must start at a sector size aligned
+ * offset, and the length must be aligned too or end at
+ * the i_size (which implies the whole inlined data).
+ */
+ ASSERT(key.offset == 0);
+ ASSERT(datal <= fs_info->sectorsize);
+ if (key.offset != 0 || datal > fs_info->sectorsize)
+ return -EUCLEAN;

/*
* If our extent is inline, we know we will drop or
@@ -404,7 +390,7 @@ static int btrfs_clone(struct inode *src, struct inode *inode,

ret = clone_copy_inline_extent(inode, trans, path,
&new_key, drop_start,
- datal, skip, size, buf);
+ datal, size, buf);
if (ret) {
if (ret != -EOPNOTSUPP)
btrfs_abort_transaction(trans, ret);
@@ -551,17 +537,6 @@ static noinline int btrfs_clone_files(struct file *file, struct file *file_src,
u64 bs = fs_info->sb->s_blocksize;

/*
- * TODO:
- * - split compressed inline extents. annoying: we need to
- * decompress into destination's address_space (the file offset
- * may change, so source mapping won't do), then recompress (or
- * otherwise reinsert) a subrange.
- *
- * - split destination inode's inline extents. The inline extents can
- * be either compressed or non-compressed.
- */
-
- /*
* VFS's generic_remap_file_range_prep() protects us from cloning the
* eof block into the middle of a file, which would result in corruption
* if the file size is not blocksize aligned. So we don't need to check
--
2.11.0