On Mon, Nov 21, 2022 at 03:25:06PM +0530, Chandan Babu R wrote: > From: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx> > > commit 00fd1d56dd08a8ceaa9e4ee1a41fefd9f6c6bc7d upstream. > > The existing reflink remapping loop has some structural problems that > need addressing: > > The biggest problem is that we create one transaction for each extent in > the source file without accounting for the number of mappings there are > for the same range in the destination file. In other words, we don't > know the number of remap operations that will be necessary and we > therefore cannot guess the block reservation required. On highly > fragmented filesystems (e.g. ones with active dedupe) we guess wrong, > run out of block reservation, and fail. > > The second problem is that we don't actually use the bmap intents to > their full potential -- instead of calling bunmapi directly and having > to deal with its backwards operation, we could call the deferred ops > xfs_bmap_unmap_extent and xfs_refcount_decrease_extent instead. This > makes the frontend loop much simpler. > > Solve all of these problems by refactoring the remapping loops so that > we only perform one remapping operation per transaction, and each > operation only tries to remap a single extent from source to dest. > > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> > Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx> > Reported-by: Edwin Török <edwin@xxxxxxxxxx> > Tested-by: Edwin Török <edwin@xxxxxxxxxx> > [backported to 5.4.y - Tested-by above does not refer to the backport] > Signed-off-by: Chandan Babu R <chandan.babu@xxxxxxxxxx> > Acked-by: Darrick J. Wong <djwong@xxxxxxxxxx> > --- > Changelog: > V1 -> V2: > 1. Add a note in the commit message to indicate that the Tested-by > tag from the original commit is not applicable to the backport. Text now updated, thanks.
