Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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>
+8
-8
+8
-8
fs/namespace.c
+8
-8
fs/namespace.c
···
526
526
* the same CPU as the task that is spinning here.
527
527
*/
528
528
preempt_enable();
529
-
lock_mount_hash();
530
-
unlock_mount_hash();
529
+
read_seqlock_excl(&mount_lock);
530
+
read_sequnlock_excl(&mount_lock);
531
531
preempt_disable();
532
532
}
533
533
}
···
671
671
* a call to mnt_unhold_writers() in order to stop preventing write access to
672
672
* @mnt.
673
673
*
674
-
* Context: This function expects lock_mount_hash() to be held serializing
674
+
* Context: This function expects to be in mount_locked_reader scope serializing
675
675
* setting WRITE_HOLD.
676
676
* Return: On success 0 is returned.
677
677
* On error, -EBUSY is returned.
···
716
716
*
717
717
* This function can only be called after a call to mnt_hold_writers().
718
718
*
719
-
* Context: This function expects lock_mount_hash() to be held.
719
+
* Context: This function expects to be in the same mount_locked_reader scope
720
+
* as the matching mnt_hold_writers().
720
721
*/
721
722
static inline void mnt_unhold_writers(struct mount *mnt)
722
723
{
···
771
770
if (atomic_long_read(&sb->s_remove_count))
772
771
return -EBUSY;
773
772
774
-
lock_mount_hash();
773
+
guard(mount_locked_reader)();
774
+
775
775
for (struct mount *m = sb->s_mounts; m; m = m->mnt_next_for_sb) {
776
776
if (!(m->mnt.mnt_flags & MNT_READONLY)) {
777
777
err = mnt_hold_writers(m);
···
789
787
if (test_write_hold(m))
790
788
clear_write_hold(m);
791
789
}
792
-
unlock_mount_hash();
793
790
794
791
return err;
795
792
}
···
1227
1226
m->mnt_mountpoint = m->mnt.mnt_root;
1228
1227
m->mnt_parent = m;
1229
1228
1230
-
lock_mount_hash();
1229
+
guard(mount_locked_reader)();
1231
1230
mnt_add_instance(m, s);
1232
-
unlock_mount_hash();
1233
1231
}
1234
1232
1235
1233
/**