diff options
authorJeff Layton <>2011-10-12 10:57:42 -0400
committerGreg Kroah-Hartman <>2011-11-11 09:43:14 -0800
commitc56f5c1b3e815614d5bc92e19d1c7633fc1d07e2 (patch)
parentcce574ff161d0f5e4263ed28a4a3785220802922 (diff)
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 <>
1 files changed, 11 insertions, 25 deletions
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index cff678b701e0..106fd0634ab3 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1714,34 +1714,20 @@ 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);
- nfs_clear_page_tag_locked(req);
- return ret;
+ return migrate_page(mapping, newpage, page);