Hello Holger,
Thank you for your response. I see that xfs_finish_page_writeback() has been
added very recently and is called from xfs_destroy_ioend(). In my kernel
(3.18.19), the xfs_destroy_ioend() is [1]. I think it doesn't suffer from
the problem of xfs_finish_page_writeback(). Looking at other usage of
"b_this_page" in my kernel, they all seem valid, and similar to what Linus's
tree has.
Looking at b_private usage to link buffer heads, the only suspicious code is
in xfs_submit_ioend():
for (bh = ioend->io_buffer_head; bh; bh = bh->b_private) {
if (!bio) {
retry:
bio = xfs_alloc_ioend_bio(bh);
} else if (bh->b_blocknr != lastblock + 1) {
xfs_submit_ioend_bio(wbc, ioend, bio);
goto retry;
}
if (xfs_bio_add_buffer(bio, bh) != bh->b_size) {
xfs_submit_ioend_bio(wbc, ioend, bio);
goto retry;
}
lastblock = bh->b_blocknr;
}
Can it happen that when the for loop does "bh = bh->b_private", the bh has
already been completed and freed?
With this in mind, the "goto retry" also seem suspicious for the same
reason.
What do you think?
Thanks,
Alex.
[1]
STATIC void
xfs_destroy_ioend(
xfs_ioend_t *ioend)
{
struct buffer_head *bh, *next;
for (bh = ioend->io_buffer_head; bh; bh = next) {
next = bh->b_private;
bh->b_end_io(bh, !ioend->io_error);
}
mempool_free(ioend, xfs_ioend_pool);
}
-----Original Message-----
From: Holger Hoffstätte
Sent: Monday, July 18, 2016 11:18 PM
To: Alex Lyakas ; xfs@xxxxxxxxxxx
Subject: Re: xfs_vm_releasepage() causing BUG at free_buffer_head()
On 07/18/16 20:00, Alex Lyakas wrote:
Greetings XFS community,
We have hit the following BUG [1].
This is in free_buffer_head():
BUG_ON(!list_empty(&bh->b_assoc_buffers));
This is happening in a long-term mainline kernel 3.18.19.
Some googling revealed a possibly-related discussion at:
http://comments.gmane.org/gmane.linux.file-systems/105093
https://lkml.org/lkml/2016/5/30/1007
except that in our case I don't see the "WARN_ON_ONCE(delalloc)"
triggered.
Since you make it past the WARN_ONs that makes it look like this
very recent report from Friday:
http://oss.sgi.com/pipermail/xfs/2016-July/050199.html
Dave posted a patch in that thread which seems ot work fine and so
far hasn't set anything on fire, at least for me on 4.4.x.
cheers,
Holger
_______________________________________________
xfs mailing list
xfs@xxxxxxxxxxx
http://oss.sgi.com/mailman/listinfo/xfs
