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SubjectRe: [PATCH 28/30] r/o bind mounts: track numbers of writers to mounts
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> @@ -327,7 +514,30 @@ static struct vfsmount *clone_mnt(struct
>
> static inline void __mntput(struct vfsmount *mnt)
> {
> + int cpu;
> struct super_block *sb = mnt->mnt_sb;
> + /*
> + * We don't have to hold all of the locks at the
> + * same time here because we know that we're the
> + * last reference to mnt and that no new writers
> + * can come in.
> + */
> + for_each_possible_cpu(cpu) {
> + struct mnt_writer *cpu_writer = &per_cpu(mnt_writers, cpu);
> + if (cpu_writer->mnt != mnt)
> + continue;
> + spin_lock(&cpu_writer->lock);
> + atomic_add(cpu_writer->count, &mnt->__mnt_writers);
> + cpu_writer->count = 0;

I think you should also add a

cpu_writer->mnt = NULL;

here. It's not a bug, but I had to think a bit about why it's not a bug.

Miklos


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