On 13.09.2016 19:48, Mikhail Afanasyev wrote: > Hello, > > I believe the 4.4.y kernel has broken overlayfs: removing the file which is > present in lower layer, then renaming a file from upper layer to have the same > name fails with ESTALE. This pattern is used quite often, for example by > 'depmod' and 'apt-get update'. The bug only seems to happen when some of the > underlying directories are on tmpfs. This was a regression related to compat code which is only in the Ubuntu kernels and will be fixed in the next update. See: http://bugs.launchpad.net/bugs/1618572 -Stefan > > The test script (below) works fine on Ubuntu kernel 4.4.0-34-generic or earlier, > and it fails in Ubuntu kernel 4.4.0-36-generic. This corresponds to Linux 4.4.16. > > The error is: > mv: cannot move 'ovf/file.new' to 'ovf/file': Stale file handle > > While I have not performed the full bisect, there were only 3 patches touching > 'fs/overlayfs' which went into the tree between the two revisions: > https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/xenial/log/?id=b275624b3b4303d21eefd78c5b3bf04c34267e4e > > > ovl: verify upper dentry before unlink and rename > https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/xenial/commit/?id=a4452ab01db4780937d4e19861d3b841c373c3b5 > > > ovl: verify upper dentry in ovl_remove_and_whiteout() > https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/xenial/commit/?id=90089541cf2982cff69724c34f7ae9a088df9c2f > > > ovl: Copy up underlying inode's ->i_mode to overlay inode > https://git.launchpad.net/~ubuntu-kernel/ubuntu/+source/linux/+git/xenial/commit/?id=8326f3ef42b56d97d1060adff6d4ab35818e3b9a > > > Of them, the first two add a return with ESTALE error and would be the prime > suspects. > I also understand that 4.4.16 is a somewhat old kernel, but I believe the bug > may still be present in the latest linux-4.4.y -- there were no changes to the > relevant file (fs/overlayfs/dir.c) since these patches. > > > > Mikhail Afanasyev > > ~~~~~~~~ TEST SCRIPT ~~~~~~ > #!/bin/sh -ex > mkdir -p /tmp/ovf-bug-demo > cd /tmp/ovf-bug-demo > > umount ./tmpfs/ovf || true > umount ./tmpfs || true > mkdir -p tmpfs > mount -t tmpfs none tmpfs > cd tmpfs > > mkdir -p upper lower ovf work > touch lower/file > mount -t overlayfs none -o > rw,noatime,lowerdir=$PWD/lower,upperdir=$PWD/upper,workdir=$PWD/work $PWD/ovf > touch ovf/file.new > > rm ovf/file > mv ovf/file.new ovf/file > > ~~~~~~~~~ END ~~~~~~~~~~~~
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