[PATCH v5 00/19] vfs: add the ability to retry on ESTALE to several syscalls

[Jeff Layton <jlayton@redhat.com>]

This patchset is a respin of the one I sent on July 26th. The main
reason for the resend is to deal with some recent changes in namei.c
that created some merge conflicts.

This series depends on the "audit" series that I also sent on July 26th.
That set didn't need any changes, so I'm not planning to resend it.

This set is also available via the "estale" branch of my git tree:

    git://git.samba.org/jlayton/linux.git estale

I'd like to see this go in for 3.7 if at all possible.

The original cover letter text follows:

ESTALE errors are a source of pain for many users, primarily those who
are doing work on NFS. When userspace provides a path to a syscall, then
there's really little excuse for returning ESTALE. If userspace gave us
a path that we had to lookup in order to do the call, then it's not
particularly helpful to return ESTALE just because that path went stale
before we could do the actual operation.

We can and should do better here. The kernel should instead catch that
error and retry the lookup and call, while forcing a revalidation of all
dentries involved.

Unfortunately fixing this requires touching the syscalls themselves, or
at least their immediate helper functions. Not all syscalls can be
retried -- only those that take a pathname as an argument.

With this patchset, I've decided to take the relatively less
controversial approach of just having the kernel retry once when it gets
an ESTALE error. I still think that it's not as strong as it should be,
but it should improve the situation in many common cases.

I've also tried to engineer this in such a way that if we do decide that
we need to retry more than once, then it should be easy to change that
later. This should cover all of the syscalls in fs/stat.c and
fs/namei.c, and a few from fs/open.c.

Once these are merged, I'll look at adding similar handling to other
path-based syscalls in a later set. A quick look shows that we have
about 50-odd path-based syscalls that will need similar handling, so
this is just a start.

Jeff Layton (19):
  vfs: add a retry_estale helper function to handle retries on ESTALE
  vfs: add a kern_path_at function
  vfs: make fstatat retry on ESTALE errors from getattr call
  vfs: fix readlinkat to retry on ESTALE
  vfs: remove user_path_at_empty
  vfs: turn "empty" arg in getname_flags into a bool
  vfs: add new "reval" argument to kern_path_create
  vfs: fix mknodat to retry on ESTALE errors
  vfs: fix mkdir to retry on ESTALE errors
  vfs: fix symlinkat to retry on ESTALE errors
  vfs: fix linkat to retry on ESTALE errors
  vfs: make rmdir retry on ESTALE errors
  vfs: make do_unlinkat retry on ESTALE errors
  vfs: fix renameat to retry on ESTALE errors
  vfs: remove user_path_parent
  vfs: have do_sys_truncate retry once on an ESTALE error
  vfs: have faccessat retry once on an ESTALE error
  vfs: have chdir retry lookup and call once on ESTALE error
  vfs: make chroot retry once on ESTALE error

 drivers/base/devtmpfs.c |   7 +-
 fs/namei.c              | 357 ++++++++++++++++++++++++++++++------------------
 fs/open.c               | 234 ++++++++++++++++++-------------
 fs/stat.c               |  44 ++++--
 include/linux/fs.h      |  22 +++
 include/linux/namei.h   |   4 +-
 net/unix/af_unix.c      |   2 +-
 7 files changed, 422 insertions(+), 248 deletions(-)

-- 
1.7.11.2