[PATCH v2 05/10] allow disable of xattr support on mount

Eric Van Hensbergen
2022-12-18T23:24:13Z

xattr creates a lot of additional messages for 9p in
the current implementation. This allows users to
conditionalize xattr support on 9p mount if they
are on a connection with bad latency. Using this
flag is also useful when debugging other aspects
of 9p as it reduces the noise in the trace files.

Signed-off-by: Eric Van Hensbergen <evanhensbergen@icloud.com>
---
Documentation/filesystems/9p.rst | 2 ++
fs/9p/v9fs.c | 9 ++++++++-
fs/9p/v9fs.h | 3 ++-
fs/9p/vfs_super.c | 3 ++-
4 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/Documentation/filesystems/9p.rst b/Documentation/filesystems/9p.rst
index 7b5964bc8865..0e800b8f73cc 100644
--- a/Documentation/filesystems/9p.rst
+++ b/Documentation/filesystems/9p.rst
@@ -137,6 +137,8 @@ Options
This can be used to share devices/named pipes/sockets between
hosts. This functionality will be expanded in later versions.

+ noxattr do not offer xattr functions on this mount.
+
access there are four access modes.
user
if a user tries to access a file on v9fs
diff --git a/fs/9p/v9fs.c b/fs/9p/v9fs.c
index a46bf9121f11..f8e952c013f9 100644
--- a/fs/9p/v9fs.c
+++ b/fs/9p/v9fs.c
@@ -38,7 +38,7 @@ enum {
/* String options */
Opt_uname, Opt_remotename, Opt_cache, Opt_cachetag,
/* Options that take no arguments */
- Opt_nodevmap,
+ Opt_nodevmap, Opt_noxattr,
/* Access options */
Opt_access, Opt_posixacl,
/* Lock timeout option */
@@ -55,6 +55,7 @@ static const match_table_t tokens = {
{Opt_uname, "uname=%s"},
{Opt_remotename, "aname=%s"},
{Opt_nodevmap, "nodevmap"},
+ {Opt_noxattr, "noxattr"},
{Opt_cache, "cache=%s"},
{Opt_cachetag, "cachetag=%s"},
{Opt_access, "access=%s"},
@@ -149,6 +150,9 @@ int v9fs_show_options(struct seq_file *m, struct dentry *root)
if (v9ses->flags & V9FS_POSIX_ACL)
seq_puts(m, ",posixacl");

+ if (v9ses->flags & V9FS_NO_XATTR)
+ seq_puts(m, ",noxattr");
+
return p9_show_client_options(m, v9ses->clnt);
}

@@ -269,6 +273,9 @@ static int v9fs_parse_options(struct v9fs_session_info *v9ses, char *opts)
case Opt_nodevmap:
v9ses->nodev = 1;
break;
+ case Opt_noxattr:
+ v9ses->flags |= V9FS_NO_XATTR;
+ break;
case Opt_cachetag:
#ifdef CONFIG_9P_FSCACHE
kfree(v9ses->cachetag);
diff --git a/fs/9p/v9fs.h b/fs/9p/v9fs.h
index 5813967ecdf0..a08cf6618c86 100644
--- a/fs/9p/v9fs.h
+++ b/fs/9p/v9fs.h
@@ -36,7 +36,8 @@ enum p9_session_flags {
V9FS_ACCESS_SINGLE = 0x04,
V9FS_ACCESS_USER = 0x08,
V9FS_ACCESS_CLIENT = 0x10,
- V9FS_POSIX_ACL = 0x20
+ V9FS_POSIX_ACL = 0x20,
+ V9FS_NO_XATTR = 0x40
};

/* possible values of ->cache */
diff --git a/fs/9p/vfs_super.c b/fs/9p/vfs_super.c
index 65d96fa94ba2..5fc6a945bfff 100644
--- a/fs/9p/vfs_super.c
+++ b/fs/9p/vfs_super.c
@@ -64,7 +64,8 @@ v9fs_fill_super(struct super_block *sb, struct v9fs_session_info *v9ses,
sb->s_magic = V9FS_MAGIC;
if (v9fs_proto_dotl(v9ses)) {
sb->s_op = &v9fs_super_ops_dotl;
- sb->s_xattr = v9fs_xattr_handlers;
+ if (!(v9ses->flags & V9FS_NO_XATTR))
+ sb->s_xattr = v9fs_xattr_handlers;
} else {
sb->s_op = &v9fs_super_ops;
sb->s_time_max = U32_MAX;
--
2.37.2