[PATCH v2 11/19] netfs: Change ->init_request() to return an error code

[David Howells]

Change the request initialisation function to return an error code so that
the network filesystem can return a failure (ENOMEM, for example).

This will also allow ceph to abort a ->readahead() op if the server refuses
to give it a cap allowing local caching from within the netfslib framework
(errors aren't passed back through ->readahead(), so returning, say,
-ENOBUFS will cause the op to be aborted).

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: linux-cachefs@xxxxxxxxxx
---

 fs/9p/vfs_addr.c       |    3 ++-
 fs/afs/file.c          |    3 ++-
 fs/netfs/objects.c     |   41 ++++++++++++++++++++++++-----------------
 fs/netfs/read_helper.c |   20 ++++++++++++--------
 include/linux/netfs.h  |    2 +-
 5 files changed, 41 insertions(+), 28 deletions(-)

diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c
index fdc1033a1546..91d3926c9559 100644
--- a/fs/9p/vfs_addr.c
+++ b/fs/9p/vfs_addr.c
@@ -56,12 +56,13 @@ static void v9fs_issue_read(struct netfs_io_subrequest *subreq)
  * @rreq: The read request
  * @file: The file being read from
  */
-static void v9fs_init_request(struct netfs_io_request *rreq, struct file *file)
+static int v9fs_init_request(struct netfs_io_request *rreq, struct file *file)
 {
 	struct p9_fid *fid = file->private_data;
 
 	refcount_inc(&fid->count);
 	rreq->netfs_priv = fid;
+	return 0;
 }
 
 /**
diff --git a/fs/afs/file.c b/fs/afs/file.c
index b19d635eed12..6469d7f98ef5 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -359,9 +359,10 @@ static int afs_symlink_readpage(struct file *file, struct page *page)
 	return ret;
 }
 
-static void afs_init_request(struct netfs_io_request *rreq, struct file *file)
+static int afs_init_request(struct netfs_io_request *rreq, struct file *file)
 {
 	rreq->netfs_priv = key_get(afs_file_key(file));
+	return 0;
 }
 
 static bool afs_is_cache_enabled(struct inode *inode)
diff --git a/fs/netfs/objects.c b/fs/netfs/objects.c
index 986d7a9d25dd..ae18827e156b 100644
--- a/fs/netfs/objects.c
+++ b/fs/netfs/objects.c
@@ -20,27 +20,34 @@ struct netfs_io_request *netfs_alloc_request(struct address_space *mapping,
 {
 	static atomic_t debug_ids;
 	struct netfs_io_request *rreq;
+	int ret;
 
 	rreq = kzalloc(sizeof(struct netfs_io_request), GFP_KERNEL);
-	if (rreq) {
-		rreq->start	= start;
-		rreq->len	= len;
-		rreq->origin	= origin;
-		rreq->netfs_ops	= ops;
-		rreq->netfs_priv = netfs_priv;
-		rreq->mapping	= mapping;
-		rreq->inode	= file_inode(file);
-		rreq->i_size	= i_size_read(rreq->inode);
-		rreq->debug_id	= atomic_inc_return(&debug_ids);
-		INIT_LIST_HEAD(&rreq->subrequests);
-		INIT_WORK(&rreq->work, netfs_rreq_work);
-		refcount_set(&rreq->ref, 1);
-		__set_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
-		if (ops->init_request)
-			ops->init_request(rreq, file);
-		netfs_stat(&netfs_n_rh_rreq);
+	if (!rreq)
+		return ERR_PTR(-ENOMEM);
+
+	rreq->start	= start;
+	rreq->len	= len;
+	rreq->origin	= origin;
+	rreq->netfs_ops	= ops;
+	rreq->netfs_priv = netfs_priv;
+	rreq->mapping	= mapping;
+	rreq->inode	= file_inode(file);
+	rreq->i_size	= i_size_read(rreq->inode);
+	rreq->debug_id	= atomic_inc_return(&debug_ids);
+	INIT_LIST_HEAD(&rreq->subrequests);
+	INIT_WORK(&rreq->work, netfs_rreq_work);
+	refcount_set(&rreq->ref, 1);
+	__set_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
+	if (rreq->netfs_ops->init_request) {
+		ret = rreq->netfs_ops->init_request(rreq, file);
+		if (ret < 0) {
+			kfree(rreq);
+			return ERR_PTR(ret);
+		}
 	}
 
+	netfs_stat(&netfs_n_rh_rreq);
 	return rreq;
 }
 
diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
index dea085715286..b5176f4320f4 100644
--- a/fs/netfs/read_helper.c
+++ b/fs/netfs/read_helper.c
@@ -768,7 +768,7 @@ void netfs_readahead(struct readahead_control *ractl,
 				   readahead_pos(ractl),
 				   readahead_length(ractl),
 				   NETFS_READAHEAD);
-	if (!rreq)
+	if (IS_ERR(rreq))
 		goto cleanup;
 
 	if (ops->begin_cache_operation) {
@@ -842,11 +842,9 @@ int netfs_readpage(struct file *file,
 	rreq = netfs_alloc_request(folio->mapping, file, ops, netfs_priv,
 				   folio_file_pos(folio), folio_size(folio),
 				   NETFS_READPAGE);
-	if (!rreq) {
-		if (netfs_priv)
-			ops->cleanup(folio_file_mapping(folio), netfs_priv);
-		folio_unlock(folio);
-		return -ENOMEM;
+	if (IS_ERR(rreq)) {
+		ret = PTR_ERR(rreq);
+		goto alloc_error;
 	}
 
 	if (ops->begin_cache_operation) {
@@ -887,6 +885,11 @@ int netfs_readpage(struct file *file,
 out:
 	netfs_put_request(rreq, false, netfs_rreq_trace_put_hold);
 	return ret;
+alloc_error:
+	if (netfs_priv)
+		ops->cleanup(folio_file_mapping(folio), netfs_priv);
+	folio_unlock(folio);
+	return ret;
 }
 EXPORT_SYMBOL(netfs_readpage);
 
@@ -1007,12 +1010,13 @@ int netfs_write_begin(struct file *file, struct address_space *mapping,
 		goto have_folio_no_wait;
 	}
 
-	ret = -ENOMEM;
 	rreq = netfs_alloc_request(mapping, file, ops, netfs_priv,
 				   folio_file_pos(folio), folio_size(folio),
 				   NETFS_READ_FOR_WRITE);
-	if (!rreq)
+	if (IS_ERR(rreq)) {
+		ret = PTR_ERR(rreq);
 		goto error;
+	}
 	rreq->no_unlock_folio	= folio_index(folio);
 	__set_bit(NETFS_RREQ_NO_UNLOCK_FOLIO, &rreq->flags);
 	netfs_priv = NULL;
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index 7dc741d9b21b..4b99e38f73d9 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -193,7 +193,7 @@ struct netfs_io_request {
  */
 struct netfs_request_ops {
 	bool (*is_cache_enabled)(struct inode *inode);
-	void (*init_request)(struct netfs_io_request *rreq, struct file *file);
+	int (*init_request)(struct netfs_io_request *rreq, struct file *file);
 	int (*begin_cache_operation)(struct netfs_io_request *rreq);
 	void (*expand_readahead)(struct netfs_io_request *rreq);
 	bool (*clamp_length)(struct netfs_io_subrequest *subreq);