Re: [PATCH 28/30] r/o bind mounts: track numbers of writers to mounts
On Mon, 2008-02-18 at 17:10 +0100, Miklos Szeredi wrote:
>
> > + /*
> > + * 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 = _cpu(mnt_writers, cpu);
> > + if (cpu_writer->mnt != mnt)
> > + continue;
> > + spin_lock(_writer->lock);
> > + atomic_add(cpu_writer->count, >__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.
Yeah, I kinda copied the code from __clear_mnt_count() where keeping
->mnt is actually a mini optimization. But, there is certainly no
chance of that mnt popping up again after a __mntput(), so I clear it in
there now. I also added a comment explaining.
-- Dave
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Re: [PATCH 28/30] r/o bind mounts: track numbers of writers to mounts
On Mon, 2008-02-18 at 17:10 +0100, Miklos Szeredi wrote:
+ /*
+ * 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.
Yeah, I kinda copied the code from __clear_mnt_count() where keeping
-mnt is actually a mini optimization. But, there is certainly no
chance of that mnt popping up again after a __mntput(), so I clear it in
there now. I also added a comment explaining.
-- Dave
--
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the body of a message to [EMAIL PROTECTED]
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Re: [PATCH 28/30] r/o bind mounts: track numbers of writers to mounts
> @@ -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 = _cpu(mnt_writers, cpu);
> + if (cpu_writer->mnt != mnt)
> + continue;
> + spin_lock(_writer->lock);
> + atomic_add(cpu_writer->count, >__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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Re: [PATCH 28/30] r/o bind mounts: track numbers of writers to mounts
@@ -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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the body of a message to [EMAIL PROTECTED]
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