вт, 19 дек. 2017 г. в 13:02, Timofey Titovets <nefelim...@gmail.com>:
> Both, defrag ioctl and autodefrag - call btrfs_defrag_file()
> for file defragmentation.
> Kernel default target extent size - 256KiB.
> Btrfs progs default - 32MiB.
> Both bigger then maximum size of compressed extent - 128KiB.
> That lead to rewrite all compressed data on disk.
> Fix that by check compression extents with different logic.
> As addition, make should_defrag_range() understood compressed extent
type,
> if requested target compression are same as current extent compression
type.
> Just don't recompress/rewrite extents.
> To avoid useless recompression of compressed extents.
> Signed-off-by: Timofey Titovets <nefelim...@gmail.com>
> ---
> fs/btrfs/ioctl.c | 28 +++++++++++++++++++++++++---
> 1 file changed, 25 insertions(+), 3 deletions(-)
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 45a47d0891fc..b29ea1f0f621 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -1008,7 +1008,7 @@ static bool defrag_check_next_extent(struct inode
*inode, struct extent_map *em)
> static int should_defrag_range(struct inode *inode, u64 start, u32
thresh,
> u64 *last_len, u64 *skip, u64 *defrag_end,
> - int compress)
> + int compress, int compress_type)
> {
> struct extent_map *em;
> int ret = 1;
> @@ -1043,8 +1043,29 @@ static int should_defrag_range(struct inode
*inode, u64 start, u32 thresh,
> * real extent, don't bother defragging it
> */
> if (!compress && (*last_len == 0 || *last_len >= thresh) &&
> - (em->len >= thresh || (!next_mergeable && !prev_mergeable)))
> + (em->len >= thresh || (!next_mergeable && !prev_mergeable))) {
> ret = 0;
> + goto out;
> + }
> +
> +
> + /*
> + * Try not recompress compressed extents
> + * thresh >= BTRFS_MAX_UNCOMPRESSED will lead to
> + * recompress all compressed extents
> + */
> + if (em->compress_type != 0 && thresh >= BTRFS_MAX_UNCOMPRESSED) {
> + if (!compress) {
> + if (em->len == BTRFS_MAX_UNCOMPRESSED)
> + ret = 0;
> + } else {
> + if (em->compress_type != compress_type)
> + goto out;
> + if (em->len == BTRFS_MAX_UNCOMPRESSED)
> + ret = 0;
> + }
> + }
> +
> out:
> /*
> * last_len ends up being a counter of how many bytes we've
defragged.
> @@ -1342,7 +1363,8 @@ int btrfs_defrag_file(struct inode *inode, struct
file *file,
> if (!should_defrag_range(inode, (u64)i << PAGE_SHIFT,
> extent_thresh, &last_len, &skip,
> - &defrag_end, do_compress)){
> + &defrag_end, do_compress,
> + compress_type)){
> unsigned long next;
> /*
> * the should_defrag function tells us how much
to skip
> --
> 2.15.1
May be, then, if we don't want add some duck tape for compressed extents
and defrag,
we can just change default kernel target extent size 256KiB -> 128KiB?
That will also fix the issue with autodefrag and compression enabled.
Thanks.
--
Have a nice day,
Timofey.
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