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

[Luis Henriques <luis@igalia.com>]

Hi Bernd,

On Fri, Feb 07 2025, Bernd Schubert wrote:

> On 1/15/25 17:32, 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 superblock dcache.
>> 
>> Signed-off-by: Luis Henriques <luis@igalia.com>
>> ---
>> Just an additional note that this patch could eventually be simplified if
>> Dave Chinner patch to iterate through the superblock inodes[1] is merged.
>> 
>> [1] https://lore.kernel.org/r/20241002014017.3801899-3-david@fromorbit.com
>> 
>>  fs/fuse/inode.c           | 53 +++++++++++++++++++++++++++++++++++++++
>>  include/uapi/linux/fuse.h |  3 +++
>>  2 files changed, 56 insertions(+)
>> 
>> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
>> index 3ce4f4e81d09..1fd9a5f303da 100644
>> --- a/fs/fuse/inode.c
>> +++ b/fs/fuse/inode.c
>> @@ -546,6 +546,56 @@ struct inode *fuse_ilookup(struct fuse_conn *fc, u64 nodeid,
>>  	return NULL;
>>  }
>>  
>> +static int fuse_reverse_inval_all(struct fuse_conn *fc)
>> +{
>> +	struct fuse_mount *fm;
>> +	struct super_block *sb;
>> +	struct inode *inode, *old_inode = NULL;
>> +	struct fuse_inode *fi;
>> +
>> +	inode = fuse_ilookup(fc, FUSE_ROOT_ID, NULL);
>> +	if (!inode)
>> +		return -ENOENT;
>> +
>> +	fm = get_fuse_mount(inode);
>> +	iput(inode);
>> +	if (!fm)
>> +		return -ENOENT;
>> +	sb = fm->sb;
>> +
>> +	spin_lock(&sb->s_inode_list_lock);
>> +	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
>> +		spin_lock(&inode->i_lock);
>> +		if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
>> +		    !atomic_read(&inode->i_count)) {
>> +			spin_unlock(&inode->i_lock);
>> +			continue;
>> +		}
>> +
>> +		__iget(inode);
>> +		spin_unlock(&inode->i_lock);
>> +		spin_unlock(&sb->s_inode_list_lock);
>> +		iput(old_inode);
>> +
>> +		fi = get_fuse_inode(inode);
>> +		spin_lock(&fi->lock);
>> +		fi->attr_version = atomic64_inc_return(&fm->fc->attr_version);
>> +		spin_unlock(&fi->lock);
>> +		fuse_invalidate_attr(inode);
>> +		forget_all_cached_acls(inode);
>> +
>> +		old_inode = inode;
>> +		cond_resched();
>> +		spin_lock(&sb->s_inode_list_lock);
>> +	}
>> +	spin_unlock(&sb->s_inode_list_lock);
>> +	iput(old_inode);
>> +
>> +	shrink_dcache_sb(sb);
>> +
>> +	return 0;
>> +}
>
> Just a suggestion, assuming Daves patch gets merged, maybe you coud move
> the actual action into into a sub function? Makes it better visible
> what is actually does and would then make it easier to move the iteration
> part to the generic approach?

Good point, I can created a helper function for that.  It may eventually
be reused if Dave's patchset moves forward.  Thanks for the suggestion.

Cheers,
-- 
Luís

> Alternatively, maybe updates Daves patch and add fuse on top of it? Dave?
>
>
> Thanks,
> Bernd
>
>