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

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Date: Thu, 28 Mar 2024 16:34:12 +0000
From: David Howells <dhowells@...hat.com>
To: Christian Brauner <christian@...uner.io>,
	Jeff Layton <jlayton@...nel.org>,
	Gao Xiang <hsiangkao@...ux.alibaba.com>,
	Dominique Martinet <asmadeus@...ewreck.org>
Cc: David Howells <dhowells@...hat.com>,
	Matthew Wilcox <willy@...radead.org>,
	Steve French <smfrench@...il.com>,
	Marc Dionne <marc.dionne@...istor.com>,
	Paulo Alcantara <pc@...guebit.com>,
	Shyam Prasad N <sprasad@...rosoft.com>,
	Tom Talpey <tom@...pey.com>,
	Eric Van Hensbergen <ericvh@...nel.org>,
	Ilya Dryomov <idryomov@...il.com>,
	netfs@...ts.linux.dev,
	linux-cachefs@...hat.com,
	linux-afs@...ts.infradead.org,
	linux-cifs@...r.kernel.org,
	linux-nfs@...r.kernel.org,
	ceph-devel@...r.kernel.org,
	v9fs@...ts.linux.dev,
	linux-erofs@...ts.ozlabs.org,
	linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org,
	netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 20/26] netfs, afs: Implement helpers for new write code

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@...hat.com>
cc: Marc Dionne <marc.dionne@...istor.com>
cc: Jeff Layton <jlayton@...nel.org>
cc: linux-afs@...ts.infradead.org
cc: netfs@...ts.linux.dev
cc: linux-fsdevel@...r.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
  */