Re: [PATCH 03/10] coda: honor AT_STATX_DONT_SYNC
On Wed, Sep 20, 2017 at 10:04 PM, Jan Harkes 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
>> Cc: Jan Harkes
>> ---
>> 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
>>
>>
Re: [PATCH 03/10] coda: honor AT_STATX_DONT_SYNC
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.
Jan
> Signed-off-by: Miklos Szeredi
> Cc: Jan Harkes
> ---
> 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
>
>
[PATCH 03/10] coda: honor AT_STATX_DONT_SYNC
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.
Signed-off-by: Miklos Szeredi
Cc: Jan Harkes
---
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
