Re: [RFC PATCH v2] fuse: add new function to invalidate cache for all inodes

[Luis Henriques]

[re-sending -- for some reason I did a simple 'reply', not a 'reply-all'.]

On Mon, Feb 10 2025, Bernd Schubert wrote:

> On 2/10/25 10:48, Luis Henriques wrote:
>> Currently userspace is able to notify the kernel to invalidate the cache for
>> an inode.  This means that, if all the inodes in a filesystem need to be
>> invalidated, then userspace needs to iterate through all of them and do this
>> kernel notification separately.
>> 
>> This patch adds a new option that allows userspace to invalidate all the
>> inodes with a single notification operation.  In addition to invalidate all
>> the inodes, it also shrinks the sb dcache.
>> 
>> Signed-off-by: Luis Henriques <luis@xxxxxxxxxx>
>> ---
>> Hi!
>> 
>> As suggested by Bernd, this patch v2 simply adds an helper function that
>> will make it easier to replace most of it's code by a call to function
>> super_iter_inodes() when Dave Chinner's patch[1] eventually gets merged.
>> 
>> [1] https://lore.kernel.org/r/20241002014017.3801899-3-david@xxxxxxxxxxxxx
>> 
>>  fs/fuse/inode.c           | 59 +++++++++++++++++++++++++++++++++++++++
>>  include/uapi/linux/fuse.h |  3 ++
>>  2 files changed, 62 insertions(+)
>> 
>> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
>> index e9db2cb8c150..be51b53006d8 100644
>> --- a/fs/fuse/inode.c
>> +++ b/fs/fuse/inode.c
>> @@ -547,6 +547,62 @@ struct inode *fuse_ilookup(struct fuse_conn *fc, u64 nodeid,
>>  	return NULL;
>>  }
>>  
>> +static void inval_single_inode(struct inode *inode, struct fuse_conn *fc)
>> +{
>> +	struct fuse_inode *fi;
>> +
>> +	fi = get_fuse_inode(inode);
>> +	spin_lock(&fi->lock);
>> +	fi->attr_version = atomic64_inc_return(&fc->attr_version);
>> +	spin_unlock(&fi->lock);
>> +	fuse_invalidate_attr(inode);
>> +	forget_all_cached_acls(inode);
>
>
> Thank you, much easier to read.
>
> Could fuse_reverse_inval_inode() call into this?

Yep, it could indeed.  I'll do that in the next iteration, thanks!

> What are the semantics 
> for  invalidate_inode_pages2_range() in this case? Totally invalidate?
> No page cache invalidation at all as right now? If so, why?

So, if I change fuse_reverse_inval_inode() to use this help, it will still
need to keep the call to invalidate_inode_pages2_range().  But in the new
function fuse_reverse_inval_all(), I'm not doing it explicitly.  Instead,
that function calls into shrink_dcache_sb().  I *think* that by doing so
the invalidation will eventually happen.  Or am I wrong assuming that?

Cheers,
-- 
Luís