| Message ID | 153923113649.5546.9840926895953408273.stgit@magnolia (mailing list archive) |
|---|---|
| Headers | show |
| Series | fs: fixes for serious clone/dedupe problems | expand |
On Thu, Oct 11, 2018 at 11:33:57AM +0300, Amir Goldstein wrote: > On Thu, Oct 11, 2018 at 7:12 AM Darrick J. Wong <darrick.wong@oracle.com> wrote: > > > > Hi all, > > > > Dave, Eric, and I have been chasing a stale data exposure bug in the XFS > > reflink implementation, and tracked it down to reflink forgetting to do > > some of the file-extending activities that must happen for regular > > writes. > > > > We then started auditing the clone, dedupe, and copyfile code and > > realized that from a file contents perspective, clonerange isn't any > > different from a regular file write. Unfortunately, we also noticed > > that *unlike* a regular write, clonerange skips a ton of overflow > > checks, such as validating the ranges against s_maxbytes, MAX_NON_LFS, > > and RLIMIT_FSIZE. We also observed that cloning into a file did not > > strip security privileges (suid, capabilities) like a regular write > > would. I also noticed that xfs and ocfs2 need to dump the page cache > > before remapping blocks, not after. > > > > In fixing the range checking problems I also realized that both dedupe > > and copyfile tell userspace how much of the requested operation was > > acted upon. Since the range validation can shorten a clone request (or > > we can ENOSPC midway through), we might as well plumb the short > > operation reporting back through the VFS indirection code to userspace. > > > > So, here's the whole giant pile of patches[1] that fix all the problems. > > This branch is against 4.19-rc7 with Dave Chinner's XFS for-next branch. > > The patch "generic: test reflink side effects" recently sent to fstests > > exercises the fixes in this series. Tests are in [2]. > > > > --D > > > > [1] https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=djwong-devel > > [2] https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfstests-dev.git/log/?h=djwong-devel > > I tested your branch with overlayfs over xfs. > I did not observe any failures with -g clone except for test generic/937 > which also failed on xfs in my test. Ok, matches what I saw overnight. Good, that means I (at least theoretically) know how to test overlayfs now. :) > I though that you forgot to mention I needed to grab xfsprogs from djwong-devel > for commit e84a9e93 ("xfs_io: dedupe command should only complain > if we don't dedupe anything"), but even with this change the test still fails: > > generic/937 - output mismatch (see > /old/home/amir/src/fstests/xfstests-dev/results//generic/937.out.bad) > --- tests/generic/937.out 2018-10-11 08:23:00.630938364 +0300 > +++ /old/home/amir/src/fstests/xfstests-dev/results//generic/937.out.bad > 2018-10-11 10:54:40.448134832 +0300 > @@ -4,8 +4,7 @@ > 39578c21e2cb9f6049b1cf7fc7be12a6 TEST_DIR/test-937/file2 > Files 1-2 do not match (intentional) > (partial) dedupe the middle blocks together > -deduped XXXX/XXXX bytes at offset XXXX > -XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec) > +XFS_IOC_FILE_EXTENT_SAME: Extents did not match. Ohhh, right, g/937 is the test to see if the dedupe implementation will return a short bytes_deduped if a single byte at the end of the range doesn't match. I'll have to update that because... I reverted the FIDEDUPERANGE behavior to set ->info[x].bytes_deduped = ->src_length even if we rounded the length down to the nearest block boundary to avoid incorrect sharing of blocks on files with non-block-aligned EOF. It turned out that the existing FIDEDUPERANGE users will hang in infinite loops if the kernel returns ->info[x].status == FILE_DEDUPE_RANGE_SAME but ->info[x].bytes_deduped < ->src_length. It seems really stupid to me that the kernel now lies to userspace to avoid breaking it, but that's what btrfs does so we're stuck with that. For now. > Compare sections > > One thing that *is* different with overlayfs test is that filefrag crashes > on this same test: > > QA output created by 937 > Create the original files > 35ac8d7917305c385c30f3d82c30a8f6 TEST_DIR/test-937/file1 > 39578c21e2cb9f6049b1cf7fc7be12a6 TEST_DIR/test-937/file2 > Files 1-2 do not match (intentional) > (partial) dedupe the middle blocks together > XFS_IOC_FILE_EXTENT_SAME: Extents did not match. > ./tests/generic/937: line 59: 19242 Floating point exception(core > dumped) ${FILEFRAG_PROG} -v $testdir/file1 >> $seqres.full > ./tests/generic/937: line 60: 19244 Floating point exception(core > dumped) ${FILEFRAG_PROG} -v $testdir/file2 >> $seqres.full > > It looks like an overlayfs v4.19-rc1 regression - FIGETBSZ returns zero. > I never noticed this regression before, because none of the generic tests > are using filefrag. Funny, I was wondering just the other day if there were any filesystems that set s_blocksize == 0... :) --D > Thanks, > Amir.