On Mon, Feb 17 2025, Bernd Schubert wrote:
> On 2/16/25 17:50, 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>
>> ---
>> fs/fuse/inode.c | 33 +++++++++++++++++++++++++++++++++
>> include/uapi/linux/fuse.h | 3 +++
>> 2 files changed, 36 insertions(+)
>>
>> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
>> index e9db2cb8c150..01a4dc5677ae 100644
>> --- a/fs/fuse/inode.c
>> +++ b/fs/fuse/inode.c
>> @@ -547,6 +547,36 @@ 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 inode *inode;
>> +
>> + inode = fuse_ilookup(fc, FUSE_ROOT_ID, &fm);
>> + if (!inode || !fm)
>> + return -ENOENT;
>> +
>> + /* Remove all possible active references to cached inodes */
>> + shrink_dcache_sb(fm->sb);
>> +
>> + /* Remove all unreferenced inodes from cache */
>> + invalidate_inodes(fm->sb);
>> +
>> + return 0;
>> +}
>> +
>> +/*
>> + * Notify to invalidate inodes cache. It can be called with @nodeid set to
>> + * either:
>> + *
>> + * - An inode number - Any pending writebacks within the rage [@offset @len]
>> + * will be triggered and the inode will be validated. To invalidate the whole
>> + * cache @offset has to be set to '0' and @len needs to be <= '0'; if @offset
>> + * is negative, only the inode attributes are invalidated.
>> + *
>> + * - FUSE_INVAL_ALL_INODES - All the inodes in the superblock are invalidated
>> + * and the whole dcache is shrinked.
>> + */
>> int fuse_reverse_inval_inode(struct fuse_conn *fc, u64 nodeid,
>> loff_t offset, loff_t len)
>> {
>> @@ -555,6 +585,9 @@ int fuse_reverse_inval_inode(struct fuse_conn *fc, u64 nodeid,
>> pgoff_t pg_start;
>> pgoff_t pg_end;
>>
>> + if (nodeid == FUSE_INVAL_ALL_INODES)
>> + return fuse_reverse_inval_all(fc);
>> +
>> inode = fuse_ilookup(fc, nodeid, NULL);
>> if (!inode)
>> return -ENOENT;
>> diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
>> index 5e0eb41d967e..e5852b63f99f 100644
>> --- a/include/uapi/linux/fuse.h
>> +++ b/include/uapi/linux/fuse.h
>> @@ -669,6 +669,9 @@ enum fuse_notify_code {
>> FUSE_NOTIFY_CODE_MAX,
>> };
>>
>> +/* The nodeid to request to invalidate all inodes */
>> +#define FUSE_INVAL_ALL_INODES 0
>> +
>> /* The read buffer is required to be at least 8k, but may be much larger */
>> #define FUSE_MIN_READ_BUFFER 8192
>>
>
>
> I think this version might end up in
>
> static void fuse_evict_inode(struct inode *inode)
> {
> struct fuse_inode *fi = get_fuse_inode(inode);
>
> /* Will write inode on close/munmap and in all other dirtiers */
> WARN_ON(inode->i_state & I_DIRTY_INODE);
>
>
> if the fuse connection has writeback cache enabled.
>
>
> Without having it tested, reproducer would probably be to run
> something like passthrough_hp (without --direct-io), opening
> and writing to a file and then sending FUSE_INVAL_ALL_INODES.
Thanks, Bernd. So far I couldn't trigger this warning. But I just found
that there's a stupid bug in the code: a missing iput() after doing the
fuse_ilookup().
I'll spend some more time trying to understand how (or if) the warning you
mentioned can triggered before sending a new revision.
Cheers,
--
Luís
