netfs: Implement unbuffered/DIO write support

Implement support for unbuffered writes and direct I/O writes.  If the
write is misaligned with respect to the fscrypt block size, then RMW cycles
are performed if necessary.  DIO writes are a special case of unbuffered
writes with extra restriction imposed, such as block size alignment
requirements.

Also provide a field that can tell the code to add some extra space onto
the bounce buffer for use by the filesystem in the case of a
content-encrypted file.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org

1 files changed, 6 insertions, 0 deletions

diff --git a/fs/netfs/internal.h b/fs/netfs/internal.h
index 886c2e8f841f..2de4f826dbe4 100644
--- a/fs/netfs/internal.h
+++ b/fs/netfs/internal.h
@@ -27,6 +27,12 @@ int netfs_prefetch_for_write(struct file *file, struct folio *folio,
 			     size_t offset, size_t len);
 
 /*
+ * direct_write.c
+ */
+ssize_t netfs_unbuffered_write_iter_locked(struct kiocb *iocb, struct iov_iter *iter,
+					   struct netfs_group *netfs_group);
+
+/*
  * io.c
  */
 int netfs_begin_read(struct netfs_io_request *rreq, bool sync);