diff options
| author | David Howells <dhowells@redhat.com> | 2022-01-27 16:02:50 +0000 |
|---|---|---|
| committer | Steve French <stfrench@microsoft.com> | 2022-02-01 10:29:18 -0600 |
| commit | bee9f65523218e3baeeecde9295c8fbe9bc08e0a (patch) | |
| tree | e13793dfdc27b40a31150029b30904f0eba699d3 /Documentation | |
| parent | 052e04a52dcd3359ba1df25a508a3a93707a3f6e (diff) | |
netfs, cachefiles: Add a method to query presence of data in the cache
Add a netfs_cache_ops method by which a network filesystem can ask the
cache about what data it has available and where so that it can make a
multipage read more efficient.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: linux-cachefs@redhat.com
Acked-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Rohith Surabattula <rohiths@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/filesystems/netfs_library.rst | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/Documentation/filesystems/netfs_library.rst b/Documentation/filesystems/netfs_library.rst index 136f8da3d0e2..4f373a8ec47b 100644 --- a/Documentation/filesystems/netfs_library.rst +++ b/Documentation/filesystems/netfs_library.rst @@ -462,6 +462,10 @@ operation table looks like the following:: struct iov_iter *iter, netfs_io_terminated_t term_func, void *term_func_priv); + + int (*query_occupancy)(struct netfs_cache_resources *cres, + loff_t start, size_t len, size_t granularity, + loff_t *_data_start, size_t *_data_len); }; With a termination handler function pointer:: @@ -536,6 +540,18 @@ The methods defined in the table are: indicating whether the termination is definitely happening in the caller's context. + * ``query_occupancy()`` + + [Required] Called to find out where the next piece of data is within a + particular region of the cache. The start and length of the region to be + queried are passed in, along with the granularity to which the answer needs + to be aligned. The function passes back the start and length of the data, + if any, available within that region. Note that there may be a hole at the + front. + + It returns 0 if some data was found, -ENODATA if there was no usable data + within the region or -ENOBUFS if there is no caching on this file. + Note that these methods are passed a pointer to the cache resource structure, not the read request structure as they could be used in other situations where there isn't a read request structure as well, such as writing dirty data to the |