[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20241107-statmount-v3-2-da5b9744c121@kernel.org>
Date: Thu, 07 Nov 2024 16:00:07 -0500
From: Jeff Layton <jlayton@...nel.org>
To: Alexander Viro <viro@...iv.linux.org.uk>,
Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>
Cc: Miklos Szeredi <miklos@...redi.hu>, Ian Kent <raven@...maw.net>,
Josef Bacik <josef@...icpanda.com>, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, Jeff Layton <jlayton@...nel.org>
Subject: [PATCH v3 2/2] fs: add the ability for statmount() to report the
mnt_devname
/proc/self/mountinfo displays the devicename for the mount, but
statmount() doesn't yet have a way to return it. Add a new
STATMOUNT_MNT_DEVNAME flag, claim the 32-bit __spare1 field to hold the
offset into the str[] array. STATMOUNT_MNT_DEVNAME will only be set in
the return mask if there is a device string.
Signed-off-by: Jeff Layton <jlayton@...nel.org>
---
fs/namespace.c | 36 +++++++++++++++++++++++++++++++++++-
include/uapi/linux/mount.h | 3 ++-
2 files changed, 37 insertions(+), 2 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index fc4f81891d544305caf863904c0a6e16562fab49..56750fcc890271e22b3b722dc0b4af445686bb86 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -5014,6 +5014,32 @@ static void statmount_fs_subtype(struct kstatmount *s, struct seq_file *seq)
seq_puts(seq, sb->s_subtype);
}
+static int statmount_mnt_devname(struct kstatmount *s, struct seq_file *seq)
+{
+ struct super_block *sb = s->mnt->mnt_sb;
+ struct mount *r = real_mount(s->mnt);
+
+ if (sb->s_op->show_devname) {
+ size_t start = seq->count;
+ int ret;
+
+ ret = sb->s_op->show_devname(seq, s->mnt->mnt_root);
+ if (ret)
+ return ret;
+
+ if (unlikely(seq_has_overflowed(seq)))
+ return -EAGAIN;
+
+ /* Unescape the result */
+ seq->buf[seq->count] = '\0';
+ seq->count = start;
+ seq_commit(seq, string_unescape_inplace(seq->buf + start, UNESCAPE_OCTAL));
+ } else if (r->mnt_devname) {
+ seq_puts(seq, r->mnt_devname);
+ }
+ return 0;
+}
+
static void statmount_mnt_ns_id(struct kstatmount *s, struct mnt_namespace *ns)
{
s->sm.mask |= STATMOUNT_MNT_NS_ID;
@@ -5077,6 +5103,10 @@ static int statmount_string(struct kstatmount *s, u64 flag)
sm->fs_subtype = start;
statmount_fs_subtype(s, seq);
break;
+ case STATMOUNT_MNT_DEVNAME:
+ sm->mnt_devname = seq->count;
+ ret = statmount_mnt_devname(s, seq);
+ break;
default:
WARN_ON_ONCE(true);
return -EINVAL;
@@ -5225,6 +5255,9 @@ static int do_statmount(struct kstatmount *s, u64 mnt_id, u64 mnt_ns_id,
if (!err && s->mask & STATMOUNT_FS_SUBTYPE)
err = statmount_string(s, STATMOUNT_FS_SUBTYPE);
+ if (!err && s->mask & STATMOUNT_MNT_DEVNAME)
+ err = statmount_string(s, STATMOUNT_MNT_DEVNAME);
+
if (!err && s->mask & STATMOUNT_MNT_NS_ID)
statmount_mnt_ns_id(s, ns);
@@ -5246,7 +5279,8 @@ static inline bool retry_statmount(const long ret, size_t *seq_size)
}
#define STATMOUNT_STRING_REQ (STATMOUNT_MNT_ROOT | STATMOUNT_MNT_POINT | \
- STATMOUNT_FS_TYPE | STATMOUNT_MNT_OPTS | STATMOUNT_FS_SUBTYPE)
+ STATMOUNT_FS_TYPE | STATMOUNT_MNT_OPTS | \
+ STATMOUNT_FS_SUBTYPE | STATMOUNT_MNT_DEVNAME)
static int prepare_kstatmount(struct kstatmount *ks, struct mnt_id_req *kreq,
struct statmount __user *buf, size_t bufsize,
diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h
index 2e939dddf9cbabe574dafdb6cff9ad4cf9298a74..3de1b0231b639fb8ed739d65b5b5406021f74196 100644
--- a/include/uapi/linux/mount.h
+++ b/include/uapi/linux/mount.h
@@ -174,7 +174,7 @@ struct statmount {
__u32 mnt_point; /* [str] Mountpoint relative to current root */
__u64 mnt_ns_id; /* ID of the mount namespace */
__u32 fs_subtype; /* [str] Subtype of fs_type (if any) */
- __u32 __spare1[1];
+ __u32 mnt_devname; /* [str] Device string for the mount */
__u64 __spare2[48];
char str[]; /* Variable size part containing strings */
};
@@ -210,6 +210,7 @@ struct mnt_id_req {
#define STATMOUNT_MNT_NS_ID 0x00000040U /* Want/got mnt_ns_id */
#define STATMOUNT_MNT_OPTS 0x00000080U /* Want/got mnt_opts */
#define STATMOUNT_FS_SUBTYPE 0x00000100U /* Want/got fs_subtype */
+#define STATMOUNT_MNT_DEVNAME 0x00000200U /* Want/got mnt_devname */
/*
* Special @mnt_id values that can be passed to listmount
--
2.47.0
Powered by blists - more mailing lists