On Mon, Apr 24, 2017 at 12:14 PM, Amir Goldstein <amir73il@xxxxxxxxx> wrote:
> Miklos,
>
> Following your comments on the 'stable inodes' series from last week,
> this series fixes constant inode numbers for stat(2) with any layer
> configuration.
>
> For the case of all *lower* layers on same fs that supports NFS export,
> redirect by file handle will be used to optimize the lookup of the copy
> up origin of non-dir inode.
>
> For the case of *all* layers on same fs, overlayfs also gains:
> - Persistent inode numbers for directories
> - Correct results for du -x
>
> Consistcy of stat(2) st_ino with readdir(3) d_ino is NOT addressed by
> this series. It will be addressed for the 'samefs' configuration by the
> follow up 'stable inode' work, which is also going to address preserving
> hardlinks on copy up.
>
> This series is available for testing on [1].
> unionmount-testsuite needs a small fix patch for layers_check() [2].
> Tested the following layer configurations:
> ./run --ov{,=0,=10} {,--samefs}
Miklos,
I instrumented unionmount-testsuite to mount cycle and compare ino
with pre copy up ino after rename and link operations [2].
It found one bug w.r.t. inode number of hardlinks, i.e.:
./run --ov hard-link
/mnt/a/no_foo100: inode number wrong (got 18833, want 17406)
I posted a 12th patch ("ovl: persistent inode numbers for hardlinks")
that fixes this issue, but I am not sure about 2 things:
1. The fix may not be so elegant (d_drop after d_instantiate)
2. Should broken hardlinks report the same inode number?
Without patch 12, broken hardlinks do report the same (lower) ino,
but only after ovl_lookup(). After ovl_link() the target reports the upper ino.
Patch 12 fixes the ovl_link() case, but I'm not sure if that is the
desired outcome.
>
> Tested constant inode numbers with xfstest overlay/017 and added a check
> for persistent directory inode numbers across mount cycle [3].
>
> Most of the patches in this series you already reviewed at one time or another
> and have your comments already addressed. Some other patches are trivial.
> Probably the only patches you need to take a closer look at are the 2 lookup
> patches (5-6).
>
> The implementation of lookup of a merged dir with a combination of redirect
> by fh from upper and redirect by name in mid layer is more complicated.
> Because this case is not strictly needed for this series, I simplified
> things a bit and restricted lookup by fh to those cases:
> 1. Non directory (lookup of copy up origin)
> 2. Merge directory when ofs->numlower == 1
>
> This restriction may be relaxed later on if we want to handle lookup by fh
> with fallback to lookup by path for merge dirs.
>
> What do you say? ... Too late for v4.12?
>
> Amir.
>
> [1] https://github.com/amir73il/linux/commits/ovl-constino
> [2] https://github.com/amir73il/unionmount-testsuite/commits/overlayfs-devel
> [3] https://github.com/amir73il/xfstests/commits/overlayfs-devel
>
> Amir Goldstein (11):
> ovl: store path type in dentry
> ovl: cram opaque boolean into type flags
> ovl: check if all layers are on the same fs
> ovl: store file handle of lower inode on copy up
> ovl: lookup redirect by file handle
> ovl: lookup non-dir inode copy up origin
> ovl: set the COPYUP type flag for non-dirs
> ovl: redirect non-dir by path on rename
> ovl: constant st_ino/st_dev across copy up
> ovl: persistent inode number for directories
> ovl: fix du --one-file-system on overlay mount
>
> fs/overlayfs/copy_up.c | 98 +++++++++++++++++++++
> fs/overlayfs/dir.c | 28 +++++-
> fs/overlayfs/inode.c | 21 ++++-
> fs/overlayfs/namei.c | 216 +++++++++++++++++++++++++++++++++++++++++------
> fs/overlayfs/overlayfs.h | 23 +++++
> fs/overlayfs/ovl_entry.h | 9 +-
> fs/overlayfs/super.c | 21 +++++
> fs/overlayfs/util.c | 83 ++++++++++++++++--
> 8 files changed, 461 insertions(+), 38 deletions(-)
>
> --
> 2.7.4
>
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