Messages in this thread | | | From | Miklos Szeredi <> | Date | Thu, 21 Sep 2017 14:45:30 +0200 | Subject | Re: [PATCH 03/10] coda: honor AT_STATX_DONT_SYNC |
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On Wed, Sep 20, 2017 at 10:04 PM, Jan Harkes <jaharkes@cs.cmu.edu> wrote: > On Wed, Sep 20, 2017 at 10:39:58AM +0200, Miklos Szeredi wrote: >> The description of this flag says "Don't sync attributes with the server". >> In other words: always use the attributes cached in the kernel and don't >> send network or local messages to refresh the attributes. > > What is the use case for this AT_STATX_DONT_SYNC flag? > > I'm asking because the Coda userspace client potentially has attributes > that are not cached in the kernel but can be (re-)validated without > network communication. So if we just care about avoiding network > traffic we could propagate the flag up to userspace. If we want to avoid > context switches, disk I/O and only check on what happens to be cached > in the kernel the current approach works fine.
It's an interesting question, "server" could mean several different things depending on the context. I interpreted it as "any entity outside the kernel the filesystem resides in", mainly because it's the simplest interpretation.
Thanks, Miklos
>> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> >> Cc: Jan Harkes <jaharkes@cs.cmu.edu> >> --- >> fs/coda/inode.c | 5 ++++- >> 1 file changed, 4 insertions(+), 1 deletion(-) >> >> diff --git a/fs/coda/inode.c b/fs/coda/inode.c >> index 6058df380cc0..734672b2cbdc 100644 >> --- a/fs/coda/inode.c >> +++ b/fs/coda/inode.c >> @@ -255,7 +255,10 @@ static void coda_evict_inode(struct inode *inode) >> int coda_getattr(const struct path *path, struct kstat *stat, >> u32 request_mask, unsigned int flags) >> { >> - int err = coda_revalidate_inode(d_inode(path->dentry)); >> + int err = 0; >> + >> + if (!(flags & AT_STATX_DONT_SYNC)) >> + err = coda_revalidate_inode(d_inode(path->dentry)); >> if (!err) >> generic_fillattr(d_inode(path->dentry), stat); >> return err; >> -- >> 2.5.5 >> >>
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