From: Larry Chen <lchen@xxxxxxxx> Subject: ocfs2: fix crash in ocfs2_duplicate_clusters_by_page() ocfs2_duplicate_clusters_by_page() may crash if one of the extent's pages is dirty. When a page has not been written back, it is still in dirty state. If ocfs2_duplicate_clusters_by_page() is called against the dirty page, the crash happens. To fix this bug, we can just unlock the page and wait until the page until its not dirty. The following is the backtrace: kernel BUG at /root/code/ocfs2/refcounttree.c:2961! [exception RIP: ocfs2_duplicate_clusters_by_page+822] __ocfs2_move_extent+0x80/0x450 [ocfs2] ? __ocfs2_claim_clusters+0x130/0x250 [ocfs2] ocfs2_defrag_extent+0x5b8/0x5e0 [ocfs2] __ocfs2_move_extents_range+0x2a4/0x470 [ocfs2] ocfs2_move_extents+0x180/0x3b0 [ocfs2] ? ocfs2_wait_for_recovery+0x13/0x70 [ocfs2] ocfs2_ioctl_move_extents+0x133/0x2d0 [ocfs2] ocfs2_ioctl+0x253/0x640 [ocfs2] do_vfs_ioctl+0x90/0x5f0 SyS_ioctl+0x74/0x80 do_syscall_64+0x74/0x140 entry_SYSCALL_64_after_hwframe+0x3d/0xa2 Once we find the page is dirty, we do not wait until it's clean, rather we use write_one_page() to write it back Link: http://lkml.kernel.org/r/20180829074740.9438-1-lchen@xxxxxxxx [lchen@xxxxxxxx: update comments] Link: http://lkml.kernel.org/r/20180830075041.14879-1-lchen@xxxxxxxx [akpm@xxxxxxxxxxxxxxxxxxxx: coding-style fixes] Signed-off-by: Larry Chen <lchen@xxxxxxxx> Acked-by: Changwei Ge <ge.changwei@xxxxxxx> Cc: Mark Fasheh <mark@xxxxxxxxxx> Cc: Joel Becker <jlbec@xxxxxxxxxxxx> Cc: Junxiao Bi <junxiao.bi@xxxxxxxxxx> Cc: Joseph Qi <jiangqi903@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/ocfs2/refcounttree.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) --- a/fs/ocfs2/refcounttree.c~fix-crash-on-ocfs2_duplicate_clusters_by_page +++ a/fs/ocfs2/refcounttree.c @@ -2946,6 +2946,7 @@ int ocfs2_duplicate_clusters_by_page(han if (map_end & (PAGE_SIZE - 1)) to = map_end & (PAGE_SIZE - 1); +retry: page = find_or_create_page(mapping, page_index, GFP_NOFS); if (!page) { ret = -ENOMEM; @@ -2954,11 +2955,18 @@ int ocfs2_duplicate_clusters_by_page(han } /* - * In case PAGE_SIZE <= CLUSTER_SIZE, This page - * can't be dirtied before we CoW it out. + * In case PAGE_SIZE <= CLUSTER_SIZE, we do not expect a dirty + * page, so write it back. */ - if (PAGE_SIZE <= OCFS2_SB(sb)->s_clustersize) - BUG_ON(PageDirty(page)); + if (PAGE_SIZE <= OCFS2_SB(sb)->s_clustersize) { + if (PageDirty(page)) { + /* + * write_on_page will unlock the page on return + */ + ret = write_one_page(page); + goto retry; + } + } if (!PageUptodate(page)) { ret = block_read_full_page(page, ocfs2_get_block); _
