From decbd919f4bb9cb698486880c026c4104b13d3c3 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Tue, 6 Sep 2011 02:37:06 -0400 Subject: [PATCH] ext4: only call ext4_jbd2_file_inode when an inode has been extended In delayed allocation mode, it's important to only call ext4_jbd2_file_inode when the file has been extended. This is necessary to avoid a race which first got introduced in commit 678aaf481, but which was made much more common with the introduction of the "punch hole" functionality. (Especially when dioread_nolock was enabled; when I could reliably reproduce this problem with xfstests #74.) The race is this: If while trying to writeback a delayed allocation inode, there is a need to map delalloc blocks, and we run out of space in the journal, *and* at the same time the inode is already on the committing transaction's t_inode_list (because for example while doing the punch hole operation, ext4_jbd2_file_inode() is called), then the commit operation will wait for the inode to finish all of its pending writebacks by calling filemap_fdatawait(), but since that inode has one or more pages with the PageWriteback flag set, the commit operation will wait forever, and the so the writeback of the inode can never take place, and the kjournald thread and the writeback thread end up waiting for each other --- forever. It's important at this point to recall why an inode is placed on the t_inode_list; it is to provide the data=ordered guarantees that we don't end up exposing stale data. In the case where we are truncating or punching a hole in the inode, there is no possibility that stale data could be exposed in the first place, so we don't need to put the inode on the t_inode_list! The right long-term fix is to get rid of data=ordered mode altogether, and only update the extent tree or indirect blocks after the data has been written. Until then, this change will also avoid some unnecessary waiting in the commit operation. Signed-off-by: "Theodore Ts'o" Cc: Allison Henderson Cc: Jan Kara --- fs/ext4/inode.c | 23 ++++++++--------------- 1 file changed, 8 insertions(+), 15 deletions(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index d1b1ef71e5b7..f86b149fb8b1 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -1471,13 +1471,13 @@ static void mpage_da_map_and_submit(struct mpage_da_data *mpd) for (i = 0; i < map.m_len; i++) unmap_underlying_metadata(bdev, map.m_pblk + i); - } - if (ext4_should_order_data(mpd->inode)) { - err = ext4_jbd2_file_inode(handle, mpd->inode); - if (err) - /* This only happens if the journal is aborted */ - return; + if (ext4_should_order_data(mpd->inode)) { + err = ext4_jbd2_file_inode(handle, mpd->inode); + if (err) + /* Only if the journal is aborted */ + return; + } } /* @@ -3173,12 +3173,8 @@ int ext4_discard_partial_page_buffers_no_lock(handle_t *handle, err = 0; if (ext4_should_journal_data(inode)) { err = ext4_handle_dirty_metadata(handle, inode, bh); - } else { - if (ext4_should_order_data(inode) && - EXT4_I(inode)->jinode) - err = ext4_jbd2_file_inode(handle, inode); + } else mark_buffer_dirty(bh); - } BUFFER_TRACE(bh, "Partial buffer zeroed"); next: @@ -3301,11 +3297,8 @@ int ext4_block_zero_page_range(handle_t *handle, err = 0; if (ext4_should_journal_data(inode)) { err = ext4_handle_dirty_metadata(handle, inode, bh); - } else { - if (ext4_should_order_data(inode) && EXT4_I(inode)->jinode) - err = ext4_jbd2_file_inode(handle, inode); + } else mark_buffer_dirty(bh); - } unlock: unlock_page(page); -- 2.39.2