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SubjectRe: [PATCH 0/3] VFS: name lookup improvements.
On Thu, Nov 09 2017, Jeff Layton wrote:

> On Thu, 2017-11-09 at 18:20 +1100, NeilBrown wrote:
>> These three patches address two issues: d_weak_revalidate and
>> path_mountpoint lookups.
>>
>> The former is poorly defined and doesn't actually do the one thing
>> that it would be useful for it to do. So the nfs implemention
>> is improved, the 9p one discarded, and the documentation clarified.
>>
>> Given this change and recent change to follow_automount() the
>> mountpoint path lookup functions are no longer needed. The regular
>> path look functions are quite sufficient.
>> The second two patches remove this with detailed explanation of why
>> it is OK.
>>
>> Thanks,
>> NeilBrown
>>
>>
>> ---
>>
>> NeilBrown (3):
>> VFS/nfs/9p: revise meaning of d_weak_invalidate.
>> VFS: remove user_path_mountpoint_at()
>> VFS / autofs4: remove kern_path_mountpoint()
>>
>>
>> Documentation/filesystems/porting | 5 +
>> Documentation/filesystems/vfs.txt | 11 +--
>> fs/9p/vfs_dentry.c | 1
>> fs/autofs4/dev-ioctl.c | 5 -
>> fs/internal.h | 1
>> fs/namei.c | 150 -------------------------------------
>> fs/namespace.c | 2
>> fs/nfs/dir.c | 60 ++-------------
>> include/linux/namei.h | 1
>> 9 files changed, 24 insertions(+), 212 deletions(-)
>>
>> --
>> Signature
>>
>
> I love that diffstat and I think the patches and the logic behind them
> look reasonable. I'm the one that added d_weak_revalidate and while it
> did fix a problem at the time, it has always seemed a bit of an odd
> d_op.
>
> Your patch does make me wonder if we should consider merging
> d_weak_revalidate and d_revalidate back together, and simply require all
> the d_revalidate ops vet the flags more thoroughly.

This boils down to adding

if (flags & LOOKUP_JUMPED)
return 1;

to the front of almost every d_revalidate function.
I'm probably in favour of that, but it isn't an obvious win.
I can certainly offer it as a follow-on patch so we can see
exactly the impact.

Thanks,
NeilBrown
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