From 8bedd51b6121c4607784d75f852828d25d119c52 Mon Sep 17 00:00:00 2001 From: Mitch Harder Date: Thu, 26 Jan 2012 15:01:11 -0500 Subject: [PATCH] Btrfs: Check for NULL page in extent_range_uptodate A user has encountered a NULL pointer kernel oops in btrfs when encountering media errors. The problem has been identified as an unhandled NULL pointer returned from find_get_page(). This modification simply checks for a NULL page, and returns with an error if found (the extent_range_uptodate() function returns 1 on errors). After testing this patch, the user reported that the error with the NULL pointer oops was solved. However, there is still a remaining problem with a thread becoming stuck in wait_on_page_locked(page) in the read_extent_buffer_pages(...) function in extent_io.c for (i = start_i; i < num_pages; i++) { page = extent_buffer_page(eb, i); wait_on_page_locked(page); if (!PageUptodate(page)) ret = -EIO; } This patch leaves the issue with the locked page yet to be resolved. Signed-off-by: Mitch Harder Signed-off-by: Chris Mason --- fs/btrfs/extent_io.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 9d09a4f..fcf77e1 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -3909,6 +3909,8 @@ int extent_range_uptodate(struct extent_io_tree *tree, while (start <= end) { index = start >> PAGE_CACHE_SHIFT; page = find_get_page(tree->mapping, index); + if (!page) + return 1; uptodate = PageUptodate(page); page_cache_release(page); if (!uptodate) { -- 2.7.4