[PATCH 20/26] netfs, afs: Implement helpers for new write code

David Howells
2024-03-28T16:38:31Z

Implement the helpers for the new write code in afs. There's now an
optional ->prepare_write() that allows the filesystem to set the parameters
for the next write, such as maximum size and maximum segment count, and an
->issue_write() that is called to initiate an (asynchronous) write
operation.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-afs@lists.infradead.org
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
---
fs/afs/file.c | 3 +++
fs/afs/internal.h | 3 +++
fs/afs/write.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 52 insertions(+)

diff --git a/fs/afs/file.c b/fs/afs/file.c
index dfd8f60f5e1f..db9ebae84fa2 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -400,6 +400,9 @@ const struct netfs_request_ops afs_req_ops = {
.update_i_size = afs_update_i_size,
.invalidate_cache = afs_netfs_invalidate_cache,
.create_write_requests = afs_create_write_requests,
+ .begin_writeback = afs_begin_writeback,
+ .prepare_write = afs_prepare_write,
+ .issue_write = afs_issue_write,
};

static void afs_add_open_mmap(struct afs_vnode *vnode)
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index b93aa026daa4..dcf0ae0323d3 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -1598,6 +1598,9 @@ extern int afs_check_volume_status(struct afs_volume *, struct afs_operation *);
/*
* write.c
*/
+void afs_prepare_write(struct netfs_io_subrequest *subreq);
+void afs_issue_write(struct netfs_io_subrequest *subreq);
+void afs_begin_writeback(struct netfs_io_request *wreq);
extern int afs_writepages(struct address_space *, struct writeback_control *);
extern int afs_fsync(struct file *, loff_t, loff_t, int);
extern vm_fault_t afs_page_mkwrite(struct vm_fault *vmf);
diff --git a/fs/afs/write.c b/fs/afs/write.c
index 1bc26466eb72..89b073881cac 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -194,6 +194,52 @@ void afs_create_write_requests(struct netfs_io_request *wreq, loff_t start, size
netfs_queue_write_request(subreq);
}

+/*
+ * Writeback calls this when it finds a folio that needs uploading. This isn't
+ * called if writeback only has copy-to-cache to deal with.
+ */
+void afs_begin_writeback(struct netfs_io_request *wreq)
+{
+ wreq->io_streams[0].avail = true;
+}
+
+/*
+ * Prepare a subrequest to write to the server. This sets the max_len
+ * parameter.
+ */
+void afs_prepare_write(struct netfs_io_subrequest *subreq)
+{
+ //if (test_bit(NETFS_SREQ_RETRYING, &subreq->flags))
+ // subreq->max_len = 512 * 1024;
+ //else
+ subreq->max_len = 256 * 1024 * 1024;
+}
+
+/*
+ * Issue a subrequest to write to the server.
+ */
+void afs_issue_write(struct netfs_io_subrequest *subreq)
+{
+ struct afs_vnode *vnode = AFS_FS_I(subreq->rreq->inode);
+ ssize_t ret;
+
+ _enter("%x[%x],%zx",
+ subreq->rreq->debug_id, subreq->debug_index, subreq->io_iter.count);
+
+#if 0 // Error injection
+ if (subreq->debug_index == 3)
+ return netfs_write_subrequest_terminated(subreq, -ENOANO, false);
+
+ if (!test_bit(NETFS_SREQ_RETRYING, &subreq->flags)) {
+ set_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags);
+ return netfs_write_subrequest_terminated(subreq, -EAGAIN, false);
+ }
+#endif
+
+ ret = afs_store_data(vnode, &subreq->io_iter, subreq->start);
+ netfs_write_subrequest_terminated(subreq, ret < 0 ? ret : subreq->len, false);
+}
+
/*
* write some of the pending data back to the server
*/