Commit 712da38d134b for kernel
commit 712da38d134b6681946368dd5c9400b43eb772b0
Author: Remi Pommarel <repk@triplefau.lt>
Date: Thu May 21 11:40:32 2026 +0200
9p: Enable symlink caching in page cache
Currently, when cache=loose is enabled, file reads are cached in the
page cache, but symlink reads are not. This patch allows the results
of p9_client_readlink() to be stored in the page cache, eliminating
the need for repeated 9P transactions on subsequent symlink accesses.
This change improves performance for workloads that involve frequent
symlink resolution.
Signed-off-by: Remi Pommarel <repk@triplefau.lt>
Message-ID: <982462d17c0c0d2856763266a25eb04d080c1dbb.1779355927.git.repk@triplefau.lt>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c
index 862164181bac..2b6ca573f955 100644
--- a/fs/9p/vfs_addr.c
+++ b/fs/9p/vfs_addr.c
@@ -70,11 +70,34 @@ static void v9fs_issue_read(struct netfs_io_subrequest *subreq)
{
struct netfs_io_request *rreq = subreq->rreq;
struct p9_fid *fid = rreq->netfs_priv;
+ char *target;
unsigned long long pos = subreq->start + subreq->transferred;
- int total, err;
-
- total = p9_client_read(fid, pos, &subreq->io_iter, &err);
+ int total = 0, err, len, n;
+
+ if (S_ISLNK(rreq->inode->i_mode)) {
+ /* p9_client_readlink() must not be called for legacy protocols
+ * 9p2000 or 9p2000.u.
+ */
+ BUG_ON(!p9_is_proto_dotl(fid->clnt));
+ if (WARN_ON_ONCE(pos)) {
+ /* reading a link at a non null offset should
+ * not happen
+ */
+ err = -EIO;
+ goto fill_subreq;
+ }
+ err = p9_client_readlink(fid, &target);
+ if (err != 0)
+ goto fill_subreq;
+ len = strlen(target);
+ n = copy_to_iter(target, len, &subreq->io_iter);
+ kfree(target);
+ total = n;
+ } else {
+ total = p9_client_read(fid, pos, &subreq->io_iter, &err);
+ }
+fill_subreq:
/* if we just extended the file size, any portion not in
* cache won't be on server and is zeroes */
if (subreq->rreq->origin != NETFS_UNBUFFERED_READ &&
@@ -99,6 +122,7 @@ static void v9fs_issue_read(struct netfs_io_subrequest *subreq)
static int v9fs_init_request(struct netfs_io_request *rreq, struct file *file)
{
struct p9_fid *fid;
+ struct dentry *dentry;
bool writing = (rreq->origin == NETFS_READ_FOR_WRITE ||
rreq->origin == NETFS_WRITETHROUGH ||
rreq->origin == NETFS_UNBUFFERED_WRITE ||
@@ -115,6 +139,14 @@ static int v9fs_init_request(struct netfs_io_request *rreq, struct file *file)
if (!fid)
goto no_fid;
p9_fid_get(fid);
+ } else if (S_ISLNK(rreq->inode->i_mode)) {
+ dentry = d_find_any_alias(rreq->inode);
+ if (!dentry)
+ goto no_fid;
+ fid = v9fs_fid_lookup(dentry);
+ dput(dentry);
+ if (IS_ERR(fid))
+ goto no_fid;
} else {
fid = v9fs_fid_find_inode(rreq->inode, writing, INVALID_UID, true);
if (!fid)
diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index a178e8cb2c82..cdaa5034cbef 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -302,10 +302,12 @@ int v9fs_init_inode(struct v9fs_session_info *v9ses,
goto error;
}
- if (v9fs_proto_dotl(v9ses))
+ if (v9fs_proto_dotl(v9ses)) {
inode->i_op = &v9fs_symlink_inode_operations_dotl;
- else
+ inode_nohighmem(inode);
+ } else {
inode->i_op = &v9fs_symlink_inode_operations;
+ }
break;
case S_IFDIR:
diff --git a/fs/9p/vfs_inode_dotl.c b/fs/9p/vfs_inode_dotl.c
index fae324681ff3..8b056c334c2b 100644
--- a/fs/9p/vfs_inode_dotl.c
+++ b/fs/9p/vfs_inode_dotl.c
@@ -686,9 +686,11 @@ v9fs_vfs_symlink_dotl(struct mnt_idmap *idmap, struct inode *dir,
int err;
kgid_t gid;
const unsigned char *name;
+ struct v9fs_session_info *v9ses;
struct p9_qid qid;
struct p9_fid *dfid;
struct p9_fid *fid = NULL;
+ struct inode *inode;
name = dentry->d_name.name;
p9_debug(P9_DEBUG_VFS, "%lu,%s,%s\n", dir->i_ino, name, symname);
@@ -712,6 +714,26 @@ v9fs_vfs_symlink_dotl(struct mnt_idmap *idmap, struct inode *dir,
v9fs_invalidate_inode_attr(dir);
+ /* instantiate inode and assign the unopened fid to the dentry */
+ fid = p9_client_walk(dfid, 1, &name, 1);
+ if (IS_ERR(fid)) {
+ err = PTR_ERR(fid);
+ p9_debug(P9_DEBUG_VFS, "p9_client_walk failed %d\n",
+ err);
+ goto error;
+ }
+
+ v9ses = v9fs_inode2v9ses(dir);
+ inode = v9fs_get_new_inode_from_fid(v9ses, fid, dir->i_sb);
+ if (IS_ERR(inode)) {
+ err = PTR_ERR(inode);
+ p9_debug(P9_DEBUG_VFS, "inode creation failed %d\n",
+ err);
+ goto error;
+ }
+ v9fs_fid_add(dentry, &fid);
+ d_instantiate(dentry, inode);
+ err = 0;
error:
p9_fid_put(fid);
p9_fid_put(dfid);
@@ -853,16 +875,18 @@ v9fs_vfs_mknod_dotl(struct mnt_idmap *idmap, struct inode *dir,
}
/**
- * v9fs_vfs_get_link_dotl - follow a symlink path
+ * v9fs_vfs_get_link_nocache_dotl - Resolve a symlink directly.
+ *
+ * To be used when symlink caching is not enabled.
+ *
* @dentry: dentry for symlink
* @inode: inode for symlink
* @done: destructor for return value
*/
-
static const char *
-v9fs_vfs_get_link_dotl(struct dentry *dentry,
- struct inode *inode,
- struct delayed_call *done)
+v9fs_vfs_get_link_nocache_dotl(struct dentry *dentry,
+ struct inode *inode,
+ struct delayed_call *done)
{
struct p9_fid *fid;
char *target;
@@ -884,6 +908,26 @@ v9fs_vfs_get_link_dotl(struct dentry *dentry,
return target;
}
+/**
+ * v9fs_vfs_get_link_dotl - follow a symlink path
+ * @dentry: dentry for symlink
+ * @inode: inode for symlink
+ * @done: destructor for return value
+ */
+static const char *
+v9fs_vfs_get_link_dotl(struct dentry *dentry,
+ struct inode *inode,
+ struct delayed_call *done)
+{
+ struct v9fs_session_info *v9ses;
+
+ v9ses = v9fs_inode2v9ses(inode);
+ if (v9ses->cache & (CACHE_META|CACHE_LOOSE))
+ return page_get_link(dentry, inode, done);
+
+ return v9fs_vfs_get_link_nocache_dotl(dentry, inode, done);
+}
+
int v9fs_refresh_inode_dotl(struct p9_fid *fid, struct inode *inode)
{
struct p9_stat_dotl *st;