From 60eb9e7d1a8aeec2d4371ec445e7fd4425d05017 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Wed, 12 Oct 2011 10:57:42 -0400 Subject: [PATCH] nfs: don't try to migrate pages with active requests commit 2da956523526e440ef4f4dd174e26f5ac06fe011 upstream. nfs_find_and_lock_request will take a reference to the nfs_page and will then put it if the req is already locked. It's possible though that the reference will be the last one. That put then can kick off a whole series of reference puts: nfs_page nfs_open_context dentry inode If the inode ends up being deleted, then the VFS will call truncate_inode_pages. That function will try to take the page lock, but it was already locked when migrate_page was called. The code deadlocks. Fix this by simply refusing the migration request if PagePrivate is already set, indicating that the page is already associated with an active read or write request. We've had a customer test a backported version of this patch and the preliminary results seem good. Cc: Andrea Arcangeli Reported-by: Harshula Jayasuriya Signed-off-by: Jeff Layton Signed-off-by: Trond Myklebust Signed-off-by: Greg Kroah-Hartman --- fs/nfs/write.c | 36 +++++++++++------------------------- 1 file changed, 11 insertions(+), 25 deletions(-) diff --git a/fs/nfs/write.c b/fs/nfs/write.c index 6015c7a879b..f2f80c005c0 100644 --- a/fs/nfs/write.c +++ b/fs/nfs/write.c @@ -1664,34 +1664,20 @@ out_error: int nfs_migrate_page(struct address_space *mapping, struct page *newpage, struct page *page) { - struct nfs_page *req; - int ret; + /* + * If PagePrivate is set, then the page is currently associated with + * an in-progress read or write request. Don't try to migrate it. + * + * FIXME: we could do this in principle, but we'll need a way to ensure + * that we can safely release the inode reference while holding + * the page lock. + */ + if (PagePrivate(page)) + return -EBUSY; nfs_fscache_release_page(page, GFP_KERNEL); - req = nfs_find_and_lock_request(page, false); - ret = PTR_ERR(req); - if (IS_ERR(req)) - goto out; - - ret = migrate_page(mapping, newpage, page); - if (!req) - goto out; - if (ret) - goto out_unlock; - page_cache_get(newpage); - spin_lock(&mapping->host->i_lock); - req->wb_page = newpage; - SetPagePrivate(newpage); - set_page_private(newpage, (unsigned long)req); - ClearPagePrivate(page); - set_page_private(page, 0); - spin_unlock(&mapping->host->i_lock); - page_cache_release(page); -out_unlock: - nfs_clear_page_tag_locked(req); -out: - return ret; + return migrate_page(mapping, newpage, page); } #endif -- 2.11.4.GIT