afs: Locally initialise the contents of a new symlink on creation

Since we know what the contents of a symlink will be when we create it on
the server, initialise its contents locally too to avoid the need to
download it.

Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/20241216204124.3752367-31-dhowells@redhat.com
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: dhowells

fs/afs/dir.c

@@ -1276,6 +1276,8 @@ static void afs_vnode_new_inode(struct afs_operation *op)
 	set_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags);
 	if (S_ISDIR(inode->i_mode))
 		afs_mkdir_init_dir(vnode, dvp->vnode);
+	else if (S_ISLNK(inode->i_mode))
+		afs_init_new_symlink(vnode, op);
 	if (!afs_op_error(op))
 		afs_cache_permit(vnode, op->key, vnode->cb_break, &vp->scb);
 	d_instantiate(op->dentry, inode);

fs/afs/inode.c

@@ -25,6 +25,24 @@
 #include "internal.h"
 #include "afs_fs.h"
 
+void afs_init_new_symlink(struct afs_vnode *vnode, struct afs_operation *op)
+{
+	size_t size = strlen(op->create.symlink) + 1;
+	size_t dsize = 0;
+	char *p;
+
+	if (netfs_alloc_folioq_buffer(NULL, &vnode->directory, &dsize, size,
+				      mapping_gfp_mask(vnode->netfs.inode.i_mapping)) < 0)
+		return;
+
+	vnode->directory_size = dsize;
+	p = kmap_local_folio(folioq_folio(vnode->directory, 0), 0);
+	memcpy(p, op->create.symlink, size);
+	kunmap_local(p);
+	set_bit(AFS_VNODE_DIR_READ, &vnode->flags);
+	netfs_single_mark_inode_dirty(&vnode->netfs.inode);
+}
+
 static void afs_put_link(void *arg)
 {
 	struct folio *folio = virt_to_folio(arg);
@@ -41,15 +59,31 @@ const char *afs_get_link(struct dentry *dentry, struct inode *inode,
 	char *content;
 	ssize_t ret;
 
-	if (atomic64_read(&vnode->cb_expires_at) == AFS_NO_CB_PROMISE ||
-	    !test_bit(AFS_VNODE_DIR_READ, &vnode->flags)) {
-		if (!dentry)
+	if (!dentry) {
+		/* RCU pathwalk. */
+		if (!test_bit(AFS_VNODE_DIR_READ, &vnode->flags) || !afs_check_validity(vnode))
 			return ERR_PTR(-ECHILD);
-		ret = afs_read_single(vnode, NULL);
-		if (ret < 0)
-			return ERR_PTR(ret);
+		goto good;
 	}
 
+	if (test_bit(AFS_VNODE_DIR_READ, &vnode->flags))
+		goto fetch;
+
+	ret = afs_validate(vnode, NULL);
+	if (ret < 0)
+		return ERR_PTR(ret);
+
+	if (!test_and_clear_bit(AFS_VNODE_ZAP_DATA, &vnode->flags) &&
+	    test_bit(AFS_VNODE_DIR_READ, &vnode->flags))
+		goto good;
+
+fetch:
+	ret = afs_read_single(vnode, NULL);
+	if (ret < 0)
+		return ERR_PTR(ret);
+	set_bit(AFS_VNODE_DIR_READ, &vnode->flags);
+
+good:
 	folio = folioq_folio(vnode->directory, 0);
 	folio_get(folio);
 	content = kmap_local_folio(folio, 0);

fs/afs/internal.h

@@ -1221,6 +1221,7 @@ extern void afs_fs_probe_cleanup(struct afs_net *);
  */
 extern const struct afs_operation_ops afs_fetch_status_operation;
 
+void afs_init_new_symlink(struct afs_vnode *vnode, struct afs_operation *op);
 const char *afs_get_link(struct dentry *dentry, struct inode *inode,
 			 struct delayed_call *callback);
 int afs_readlink(struct dentry *dentry, char __user *buffer, int buflen);

fs/netfs/buffered_read.c

@@ -210,7 +210,7 @@ static void netfs_read_to_pagecache(struct netfs_io_request *rreq)
 
 	do {
 		struct netfs_io_subrequest *subreq;
-		enum netfs_io_source source = NETFS_DOWNLOAD_FROM_SERVER;
+		enum netfs_io_source source = NETFS_SOURCE_UNKNOWN;
 		ssize_t slice;
 
 		subreq = netfs_alloc_subrequest(rreq);

fs/netfs/read_single.c

@@ -97,7 +97,7 @@ static int netfs_single_dispatch_read(struct netfs_io_request *rreq)
 	if (!subreq)
 		return -ENOMEM;
 
-	subreq->source	= NETFS_DOWNLOAD_FROM_SERVER;
+	subreq->source	= NETFS_SOURCE_UNKNOWN;
 	subreq->start	= 0;
 	subreq->len	= rreq->len;
 	subreq->io_iter	= rreq->buffer.iter;