[PATCH 17/19] netfs: Change ->init_rreq() to return an error code

[David Howells]

Change the read-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/buffered_read.c |   15 +++++++++------
 fs/netfs/objects.c       |   40 ++++++++++++++++++++++++----------------
 include/linux/netfs.h    |    2 +-
 5 files changed, 38 insertions(+), 25 deletions(-)

diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c
index 840111da1172..e50326d11e8f 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 aef0fbbd834d..2b68b2070248 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -357,9 +357,10 @@ 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 int afs_begin_cache_operation(struct netfs_io_request *rreq)
diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c
index 343c0957ae27..64049e123185 100644
--- a/fs/netfs/buffered_read.c
+++ b/fs/netfs/buffered_read.c
@@ -167,7 +167,7 @@ void netfs_readahead(struct readahead_control *ractl)
 				   readahead_pos(ractl),
 				   readahead_length(ractl),
 				   NETFS_READAHEAD);
-	if (!rreq)
+	if (IS_ERR(rreq))
 		return;
 
 	if (ctx->ops->begin_cache_operation) {
@@ -223,8 +223,10 @@ int netfs_readpage(struct file *file, struct page *subpage)
 
 	rreq = netfs_alloc_request(mapping, file, folio_file_pos(folio),
 				   folio_size(folio), NETFS_READPAGE);
-	if (!rreq)
-		goto nomem;
+	if (IS_ERR(rreq)) {
+		ret = PTR_ERR(rreq);
+		goto alloc_error;
+	}
 
 	if (ctx->ops->begin_cache_operation) {
 		ret = ctx->ops->begin_cache_operation(rreq);
@@ -238,7 +240,7 @@ int netfs_readpage(struct file *file, struct page *subpage)
 
 discard:
 	netfs_put_request(rreq, false, netfs_rreq_trace_put_discard);
-nomem:
+alloc_error:
 	folio_unlock(folio);
 	return ret;
 }
@@ -371,11 +373,12 @@ int netfs_write_begin(struct file *file, struct address_space *mapping,
 		goto have_folio_no_wait;
 	}
 
-	ret = -ENOMEM;
 	rreq = netfs_alloc_request(mapping, file, folio_file_pos(folio),
 				   folio_size(folio), NETFS_READ_FOR_WRITE);
-	if (!rreq)
+	if (IS_ERR(rreq)) {
+		ret = PTR_ERR(rreq);
 		goto error;
+	}
 	rreq->start		= folio_file_pos(folio);
 	rreq->len		= folio_size(folio);
 	rreq->no_unlock_folio	= folio_index(folio);
diff --git a/fs/netfs/objects.c b/fs/netfs/objects.c
index 8f99269c5344..d8a07df03427 100644
--- a/fs/netfs/objects.c
+++ b/fs/netfs/objects.c
@@ -20,26 +20,34 @@ struct netfs_io_request *netfs_alloc_request(struct address_space *mapping,
 	struct inode *inode = file ? file_inode(file) : mapping->host;
 	struct netfs_i_context *ctx = netfs_i_context(inode);
 	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->mapping	= mapping;
-		rreq->inode	= inode;
-		rreq->origin	= origin;
-		rreq->netfs_ops	= ctx->ops;
-		rreq->i_size	= i_size_read(inode);
-		rreq->debug_id	= atomic_inc_return(&debug_ids);
-		INIT_LIST_HEAD(&rreq->subrequests);
-		INIT_WORK(&rreq->work, NULL);
-		refcount_set(&rreq->ref, 1);
-		__set_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
-		if (ctx->ops->init_request)
-			ctx->ops->init_request(rreq, file);
-		netfs_stat(&netfs_n_rh_rreq);
+	if (!rreq)
+		return ERR_PTR(-ENOMEM);
+
+	rreq->start	= start;
+	rreq->len	= len;
+	rreq->mapping	= mapping;
+	rreq->inode	= inode;
+	rreq->origin	= origin;
+	rreq->netfs_ops	= ctx->ops;
+	rreq->i_size	= i_size_read(inode);
+	rreq->debug_id	= atomic_inc_return(&debug_ids);
+	INIT_LIST_HEAD(&rreq->subrequests);
+	INIT_WORK(&rreq->work, NULL);
+	refcount_set(&rreq->ref, 1);
+	__set_bit(NETFS_RREQ_IN_PROGRESS, &rreq->flags);
+
+	if (ctx->ops->init_request) {
+		ret = ctx->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/include/linux/netfs.h b/include/linux/netfs.h
index 725b8fb8e4bb..c925596c1bb3 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -202,7 +202,7 @@ struct netfs_io_request {
  * Operations the network filesystem can/must provide to the helpers.
  */
 struct netfs_request_ops {
-	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);