On Mon, Dec 16, 2019 at 06:26:54PM +0000, fdmanana@xxxxxxxxxx wrote: > From: Filipe Manana <fdmanana@xxxxxxxx> > > Hi, > > This short series allows deduplication of the last block of a file when > the eof is not aligned to the sector size, as long as the range's end > offset matches the eof of the destination file. > > This is a safe case unlike the case where we attempt to clone the block in > the middle of a file (which results in a corruption I found last year and > affected both btrfs and xfs). > > This is motivated by btrfs users reporting lower deduplication scores > starting with kernel 5.0, which was the kernel release where btrfs was > changed to use the generic VFS helper generic_remap_file_range_prep(). > Users observed that the last block was no longer deduplicated when a > file's size is not block size aligned. For btrfs this is specially > important because references are kept per extent and not per block, so > not having the last block deduplicated means the entire extent is kept > allocated, making the deduplication not effective and often pointless in > many cases. > > Thanks. > > Filipe Manana (2): > fs: allow deduplication of eof block into the end of the destination > file > Btrfs: make deduplication with range including the last block work I'm going to send pull request with these two patches once the merge window opens. git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git fs-dedupe-last-block
