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? 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. -chris - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
