diff options
| author | Al Viro <viro@zeniv.linux.org.uk> | 2025-08-27 14:04:31 -0400 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2025-09-17 15:58:29 -0400 |
| commit | 1e414adf03ae5a9928aad9044a07adeb92ddcd2c (patch) | |
| tree | 8bbfebf7f3866fa8dcc11e9920bd57bab1259131 | |
| parent | 3371fa2f27134fc4ec7d40b2ae7b9e92c3b2527e (diff) | |
WRITE_HOLD machinery: no need for to bump mount_lock seqcount
... neither for insertion into the list of instances, nor for
mnt_{un,}hold_writers(), nor for mnt_get_write_access() deciding
to be nice to RT during a busy-wait loop - all of that only needs
the spinlock side of mount_lock.
IOW, it's mount_locked_reader, not mount_writer.
Clarify the comment re locking rules for mnt_unhold_writers() - it's
not just that mount_lock needs to be held when calling that, it must
have been held all along since the matching mnt_hold_writers().
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
| -rw-r--r-- | fs/namespace.c | 16 |
1 files changed, 8 insertions, 8 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index 714e159ed9cd..54066c9b8da0 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -526,8 +526,8 @@ int mnt_get_write_access(struct vfsmount *m) * the same CPU as the task that is spinning here. */ preempt_enable(); - lock_mount_hash(); - unlock_mount_hash(); + read_seqlock_excl(&mount_lock); + read_sequnlock_excl(&mount_lock); preempt_disable(); } } @@ -671,7 +671,7 @@ EXPORT_SYMBOL(mnt_drop_write_file); * a call to mnt_unhold_writers() in order to stop preventing write access to * @mnt. * - * Context: This function expects lock_mount_hash() to be held serializing + * Context: This function expects to be in mount_locked_reader scope serializing * setting WRITE_HOLD. * Return: On success 0 is returned. * On error, -EBUSY is returned. @@ -716,7 +716,8 @@ static inline int mnt_hold_writers(struct mount *mnt) * * This function can only be called after a call to mnt_hold_writers(). * - * Context: This function expects lock_mount_hash() to be held. + * Context: This function expects to be in the same mount_locked_reader scope + * as the matching mnt_hold_writers(). */ static inline void mnt_unhold_writers(struct mount *mnt) { @@ -770,7 +771,8 @@ int sb_prepare_remount_readonly(struct super_block *sb) if (atomic_long_read(&sb->s_remove_count)) return -EBUSY; - lock_mount_hash(); + guard(mount_locked_reader)(); + for (struct mount *m = sb->s_mounts; m; m = m->mnt_next_for_sb) { if (!(m->mnt.mnt_flags & MNT_READONLY)) { err = mnt_hold_writers(m); @@ -787,7 +789,6 @@ int sb_prepare_remount_readonly(struct super_block *sb) if (test_write_hold(m)) clear_write_hold(m); } - unlock_mount_hash(); return err; } @@ -1226,9 +1227,8 @@ static void setup_mnt(struct mount *m, struct dentry *root) m->mnt_mountpoint = m->mnt.mnt_root; m->mnt_parent = m; - lock_mount_hash(); + guard(mount_locked_reader)(); mnt_add_instance(m, s); - unlock_mount_hash(); } /** |