From: Alexey Khoroshilov Subject: [PATCH] ext4: implement error handling of ext4_mb_new_preallocation() Date: Mon, 6 May 2013 00:51:15 +0400 Message-ID: <1367787075-11626-1-git-send-email-khoroshilov@ispras.ru> Cc: Alexey Khoroshilov , Andreas Dilger , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, spruce-project@linuxtesting.org To: "Theodore Ts'o" Return-path: Received: from mail.ispras.ru ([83.149.199.45]:55784 "EHLO mail.ispras.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752065Ab3EEUvz (ORCPT ); Sun, 5 May 2013 16:51:55 -0400 Sender: linux-ext4-owner@vger.kernel.org List-ID: If memory allocation in ext4_mb_new_group_pa() is failed, it returns error code, ext4_mb_new_preallocation() propages it, but ext4_mb_new_blocks() ignores it. An observed result was: - allocation fail means ext4_mb_new_group_pa() does not update ext4_allocation_context; - ext4_mb_new_blocks() sets ext4_allocation_request->len (ar->len = ac->ac_b_ex.fe_len;) to number of blocks preallocated (512) instead of number of blocks requested (1); - that activates update cycle in ext4_splice_branch(): for (i = 1; i < blks; i++) <-- blks is 512 instead of 1 here *(where->p + i) = cpu_to_le32(current_block++); - it iterates 511 times and corrupts a chunk of memory including inode structure; - page fault happens at EXT4_SB(inode->i_sb) in ext4_mark_inode_dirty(); - system hangs with 'scheduling while atomic' BUG. The patch implements a check for ext4_mb_new_preallocation() error code and handles its failure as if ext4_mb_regular_allocator() fails. Found by Linux File System Verification project (linuxtesting.org). Signed-off-by: Alexey Khoroshilov --- fs/ext4/mballoc.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index b1ed9e0..95c6b0d 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -4401,17 +4401,18 @@ ext4_fsblk_t ext4_mb_new_blocks(handle_t *handle, repeat: /* allocate space in core */ *errp = ext4_mb_regular_allocator(ac); + if (!*errp) { + /* as we've just preallocated more space than + * user requested orinally, we store allocated + * space in a special descriptor */ + if (ac->ac_status == AC_STATUS_FOUND && + ac->ac_o_ex.fe_len < ac->ac_b_ex.fe_len) + *errp = ext4_mb_new_preallocation(ac); + } if (*errp) { ext4_discard_allocated_blocks(ac); goto errout; }