Re: [PATCH 17/17] NFS: nfs_migrate_page() does not wait for FS-Cacheto finish with a page
From: Jonathan Nieder
Date: Sat Jul 21 2012 - 12:58:44 EST
In February, David Howells wrote:
> nfs_migrate_page() does not wait for FS-Cache to finish with a page, probably
> leading to the following bad-page-state:
> nfs_migrate_page() calls nfs_fscache_release_page() which doesn't actually wait
> - even if __GFP_WAIT is set. The reason that doesn't wait is that
> fscache_maybe_release_page() might deadlock the allocator as the work threads
> writing to the cache may all end up sleeping on memory allocation.
> (1) Make nfs_migrate_page() wait.
> (2) Make fscache_maybe_release_page() honour the __GFP_WAIT flag.
> (3) Set a timeout around the wait.
> (4) Make nfs_migrate_page() return an error if the page is still busy.
> For the moment, I'll select (2) and (4).
> --- a/fs/nfs/write.c
> +++ b/fs/nfs/write.c
> @@ -1701,7 +1701,9 @@ int nfs_migrate_page(struct address_space *mapping, struct page *newpage,
> if (PagePrivate(page))
> return -EBUSY;
> - nfs_fscache_release_page(page, GFP_KERNEL);
> + ret = -EBUSY;
> + if (!nfs_fscache_release_page(page, GFP_KERNEL))
> + goto out;
> return migrate_page(mapping, newpage, page, mode);
Small thing, but it looks like this was forward-ported incorrectly.
Was this ever tested with CONFIG_MIGRATION enabled?
Hope that helps,
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/