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.
This set is a first "official" pass at adding ESTALE retry handling to
various syscalls. 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.
If this approach is reasonable I'll look at adding similar handling to
other path-based vfs calls in a another 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.
Comments welcome...
Jeff Layton (12):
vfs: add a retry_estale helper function to handle retries on ESTALE
vfs: make fstatat retry on ESTALE errors from getattr call
vfs: fix readlinkat to retry on ESTALE
vfs: add new "reval" argument to kern_path_create and
user_path_create
vfs: fix mknodat to retry on ESTALE errors
vfs: fix mkdir to retry on ESTALE errors
vfs: add a "reval" flag to args for user_path_parent
vfs: make rmdir retry on ESTALE errors
vfs: make do_unlinkat retry on ESTALE errors
vfs: fix symlinkat to retry on ESTALE errors
vfs: fix linkat to retry on ESTALE errors
vfs: fix renameat to retry on ESTALE errors
arch/powerpc/platforms/cell/spufs/syscalls.c | 2 +-
drivers/base/devtmpfs.c | 7 +-
fs/namei.c | 233 +++++++++++++++-----------
fs/ocfs2/refcounttree.c | 3 +-
fs/stat.c | 32 +++-
include/linux/fs.h | 21 +++
include/linux/namei.h | 4 +-
net/unix/af_unix.c | 3 +-
8 files changed, 191 insertions(+), 114 deletions(-)
--
1.7.7.6
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