Hi,
I believe there are two more cases, where we can safely avoid shipping
disknr=0 extent. These are cases, in which the file grows between the
two snapshots, and some of the new extents are no-data extents. So the
whole patch becomes:
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 5445454..0bd96fe 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -3839,17 +3839,18 @@ static int is_extent_unchanged(struct send_ctx *sctx,
/*
* Handle special case where the right side has no extents at all.
*/
eb = path->nodes[0];
slot = path->slots[0];
btrfs_item_key_to_cpu(eb, &found_key, slot);
if (found_key.objectid != key.objectid ||
found_key.type != key.type) {
- ret = 0;
+ /* No need to send a no-data extent it in this case */
+ ret = (left_disknr == 0) ? 1 : 0;
goto out;
}
/*
* We're now on 2a, 2b or 7.
*/
key = found_key;
while (key.offset < ekey->offset + left_len) {
@@ -3865,17 +3866,18 @@ static int is_extent_unchanged(struct send_ctx *sctx,
goto out;
}
/*
* Are we at extent 8? If yes, we know the extent is changed.
* This may only happen on the first iteration.
*/
if (found_key.offset + right_len <= ekey->offset) {
- ret = 0;
+ /* No need to send a no-data extent it in this case */
+ ret = (left_disknr == 0) ? 1 : 0;
goto out;
}
left_offset_fixed = left_offset;
if (key.offset < ekey->offset) {
/* Fix the right offset for 2a and 7. */
right_offset += ekey->offset - key.offset;
} else {
@@ -3946,16 +3948,38 @@ static int process_extent(struct send_ctx *sctx,
if (sctx->parent_root && !sctx->cur_inode_new) {
ret = is_extent_unchanged(sctx, path, key);
if (ret < 0)
goto out;
if (ret) {
ret = 0;
goto out;
}
+ } else {
+ struct extent_buffer *eb;
+ struct btrfs_file_extent_item *ei;
+ u8 extent_type;
+ u64 extent_disknr;
+
+ eb = path->nodes[0];
+ ei = btrfs_item_ptr(eb, path->slots[0],
+ struct btrfs_file_extent_item);
+
+ extent_type = btrfs_file_extent_type(eb, ei);
+ extent_disknr = btrfs_file_extent_disk_bytenr(eb, ei);
+ if (extent_type == BTRFS_FILE_EXTENT_REG && extent_disknr == 0) {
+ /*
+ * This is disknr=0 extent in a full-send or a new inode
+ * in a diff-send. Since we will send truncate command
+ * in finish_inode_if_needed anyways, the inode size will be
+ * correct, and we don't have to send all-zero data.
+ */
+ ret = 0;
+ goto out;
+ }
}
ret = find_extent_clone(sctx, path, key->objectid, key->offset,
sctx->cur_inode_size, &found_clone);
if (ret != -ENOENT && ret < 0)
goto out;
ret = send_write_or_clone(sctx, path, key, found_clone);
Alex.
On Tue, Jan 8, 2013 at 6:06 PM, Alex Lyakas <alex@xxxxxxxxxxxxxxxxx> wrote:
> Hi Chen, Alexander, Jan,
> how about the following patch: it works for disknr==0 extents (to
> handle PREALLOC extents correctly, we need to add a new command, which
> will break existing btrfs-progs, because they are updated slower than
> the kernel side).
>
> diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
> index 5445454..2b46d92 100644
> --- a/fs/btrfs/send.c
> +++ b/fs/btrfs/send.c
> @@ -3946,16 +3946,38 @@ static int process_extent(struct send_ctx *sctx,
> if (sctx->parent_root && !sctx->cur_inode_new) {
> ret = is_extent_unchanged(sctx, path, key);
> if (ret < 0)
> goto out;
> if (ret) {
> ret = 0;
> goto out;
> }
> + } else {
> + struct extent_buffer *eb;
> + struct btrfs_file_extent_item *ei;
> + u8 extent_type;
> + u64 extent_disknr;
> +
> + eb = path->nodes[0];
> + ei = btrfs_item_ptr(eb, path->slots[0],
> + struct btrfs_file_extent_item);
> +
> + extent_type = btrfs_file_extent_type(eb, ei);
> + extent_disknr = btrfs_file_extent_disk_bytenr(eb, ei);
> + if (extent_type == BTRFS_FILE_EXTENT_REG &&
> extent_disknr == 0) {
> + /*
> + * This is disknr=0 extent in a full-send or a new inode
> + * in a diff-send. Since we will send truncate command
> + * in finish_inode_if_needed anyways, the
> inode size will be
> + * correct, and we don't have to send all-zero data.
> + */
> + ret = 0;
> + goto out;
> + }
> }
>
> ret = find_extent_clone(sctx, path, key->objectid, key->offset,
> sctx->cur_inode_size, &found_clone);
> if (ret != -ENOENT && ret < 0)
> goto out;
>
> ret = send_write_or_clone(sctx, path, key, found_clone);
>
> Thanks,
> Alex.
>
>
> On Thu, Nov 29, 2012 at 10:54 AM, Alexander Block <ablock84@xxxxxxxxx> wrote:
>> On Thu, Nov 29, 2012 at 4:11 AM, Chen Yang <chenyang.fnst@xxxxxxxxxxxxxx> wrote:
>>> when send/receive a sparse file, the holes of the original file
>>> will be filled with zero. The holes will be sent as ZERO streams,
>>> and it's unnecessary.
>>>
>>> So, I improved this by skipping the hole of file while sending.
>>>
>>> Signed-off-by: Cheng Yang <chenyang.fnst@xxxxxxxxxxxxxx>
>>> ---
>>> fs/btrfs/send.c | 6 ++++++
>>> 1 files changed, 6 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
>>> index e78b297..1e1d59a 100644
>>> --- a/fs/btrfs/send.c
>>> +++ b/fs/btrfs/send.c
>>> @@ -3718,6 +3718,7 @@ static int send_write_or_clone(struct send_ctx *sctx,
>>> u64 pos = 0;
>>> u64 len;
>>> u32 l;
>>> + u64 bytenr;
>>> u8 type;
>>>
>>> ei = btrfs_item_ptr(path->nodes[0], path->slots[0],
>>> @@ -3732,6 +3733,11 @@ static int send_write_or_clone(struct send_ctx *sctx,
>>> */
>>> len = PAGE_CACHE_ALIGN(len);
>>> } else {
>>> + bytenr = btrfs_file_extent_disk_bytenr(path->nodes[0], ei);
>>> + if (bytenr == 0) {
>>> + ret = 0;
>>> + goto out;
>>> + }
>>> len = btrfs_file_extent_num_bytes(path->nodes[0], ei);
>>> }
>>>
>>> --
>>> 1.7.7.6
>>>
>>> --
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>>
>> This won't work for incremental sends if I understand it correctly. If
>> the hole got punched into the file after the initial send, the data
>> will be unchanged on the receiving side when receiving incrementally.
>> --
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