Chris Mason wrote:
On Tue, 30 Oct 2007 13:54:05 -0800
Badari Pulavarty <pbadari@xxxxxxxxxx> wrote:
On Tue, 2007-10-30 at 13:54 -0400, Chris Mason wrote:
On Tue, 30 Oct 2007 10:27:04 -0800
Badari Pulavarty <pbadari@xxxxxxxxxx> wrote:
Hi,
While testing hotplug memory remove, I ran into this issue. Given
a range of pages hotplug memory remove tries to migrate those
pages.
migrate_pages() keeps failing to migrate pages containing
pagecache pages for reiserfs files. I noticed that reiserfs
doesn't have ->migratepage() ops. So, fallback_migrate_page()
code tries to do try_to_release_page(). try_to_release_page()
fails to drop_buffers() since b_count == 1. Here is what my debug
shows:
migrate pages failed pfn 258111/flags 3f00000000801
bh c00000000b53f6e0 flags 110029 count 1
Any one know why the b_count == 1 and not getting dropped to
zero ?
If these are file data pages, the count is probably elevated as
part of the data=ordered tracking. You can verify this via
b_private, or just mount data=writeback to double check.
Chris,
That was my first assumption. But after looking at
reiserfs_releasepage (), realized that it would do reiserfs_free_jh()
and clears the b_private. I couldn't easily find out who has the ref.
against this bh.
bh c00000000bdaaf00 flags 110029 count 1 private 0
If I'm reading this correctly the buffer is BH_Lock | BH_Req, perhaps
it is currently under IO?
Its BH_Req | BH_Uptodate. Its not under IO.
The page isn't locked, but data=ordered does IO directly on the buffer
heads, without taking the page lock.
The easy way to narrow our search is to try without data=ordered, it is
certainly complicating things.
I can try that, its my root filesystem :(
Thanks,
Badari
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