On Thu, Jun 4, 2015 at 12:18 PM, Robbie Ko <robbi...@synology.com> wrote:
> There's one case where we not clear orphan_dir_info issue.
You mean where we leak a orphan_dir_info structure.
>
> Example:
>
> Parent snapshot:
> |---- a/ (ino 279)
> |---- c (ino 282)
> |---- del/ (ino 281)
> |---- tmp/ (ino 280)
> |---- long/ (ino 283)
> |---- longlong/ (ino 284)
>
> Send snapshot:
> |---- a/ (ino 279)
> |---- long (ino 283)
> |---- longlong (ino 284)
> |---- c/ (ino 282)
> |---- tmp/ (ino 280)
>
> Here we process 281 use can_rmdir check, but 280 is waiting, so create
> orphan_dir_info
> and when 282 is move to dest, so 280 can move to c/tmp, and now run can_rmdir
> check again.
> Return is false, because 283 and 284 is unprocess, but now not release
> orphan_dir_info.
> When 283 and 284 is processd, 281 be delete, but not delete orphan_dir_info.
> So fix this by release orphan_dir_info for this case.
Could be described more generically as freeing an existing
orphan_dir_info for a directory, when we realize we can't rmdir the
directory because it has a descendant that wasn't yet processed, and
the orphan_dir_info was created because it had a descendant that had
its rename operation delayed.
>
> Signed-off-by: Robbie Ko <robbi...@synology.com>
> ---
> fs/btrfs/send.c | 19 ++++++++++++-------
> 1 file changed, 12 insertions(+), 7 deletions(-)
>
> diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
> index 596b9dc..ff9d052 100644
> --- a/fs/btrfs/send.c
> +++ b/fs/btrfs/send.c
> @@ -2785,12 +2785,6 @@ add_orphan_dir_info(struct send_ctx *sctx, u64 dir_ino)
> struct rb_node *parent = NULL;
> struct orphan_dir_info *entry, *odi;
>
> - odi = kmalloc(sizeof(*odi), GFP_NOFS);
> - if (!odi)
> - return ERR_PTR(-ENOMEM);
> - odi->ino = dir_ino;
> - odi->gen = 0;
> -
> while (*p) {
> parent = *p;
> entry = rb_entry(parent, struct orphan_dir_info, node);
> @@ -2799,11 +2793,16 @@ add_orphan_dir_info(struct send_ctx *sctx, u64
> dir_ino)
> } else if (dir_ino > entry->ino) {
> p = &(*p)->rb_right;
> } else {
> - kfree(odi);
> return entry;
> }
> }
>
> + odi = kmalloc(sizeof(*odi), GFP_NOFS);
> + if (!odi)
> + return ERR_PTR(-ENOMEM);
> + odi->ino = dir_ino;
> + odi->gen = 0;
> +
All the above changes don't fix the issue described in this change -
the memory leak - they just avoid the overhead of allocating an
orphan_dir_info object unnecessarily.
The change is ok, but should be a separate patch in the series that
does only that.
> rb_link_node(&odi->node, parent, p);
> rb_insert_color(&odi->node, &sctx->orphan_dirs);
> return odi;
> @@ -2913,6 +2912,12 @@ static int can_rmdir(struct send_ctx *sctx, u64 dir,
> u64 dir_gen,
> }
>
> if (loc.objectid > send_progress) {
> + struct orphan_dir_info *odi;
> +
> + odi = get_orphan_dir_info(sctx, dir);
> + if (odi) {
> + free_orphan_dir_info(sctx, odi);
> + }
Looks correct, great catch.
Thanks.
> ret = 0;
> goto out;
> }
> --
> 1.9.1
>
> --
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--
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"Reasonable men adapt themselves to the world.
Unreasonable men adapt the world to themselves.
That's why all progress depends on unreasonable men."
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