From: zhangyi (F) yi.zhang@huawei.com
[ Upstream commit c96dceeabf765d0b1b1f29c3bf50a5c01315b820 ]
Commit 904cdbd41d74 ("jbd2: clear dirty flag when revoking a buffer from an older transaction") set the BH_Freed flag when forgetting a metadata buffer which belongs to the committing transaction, it indicate the committing process clear dirty bits when it is done with the buffer. But it also clear the BH_Mapped flag at the same time, which may trigger below NULL pointer oops when block_size < PAGE_SIZE.
rmdir 1 kjournald2 mkdir 2 jbd2_journal_commit_transaction commit transaction N jbd2_journal_forget set_buffer_freed(bh1) jbd2_journal_commit_transaction commit transaction N+1 ... clear_buffer_mapped(bh1) ext4_getblk(bh2 ummapped) ... grow_dev_page init_page_buffers bh1->b_private=NULL bh2->b_private=NULL jbd2_journal_put_journal_head(jh1) __journal_remove_journal_head(hb1) jh1 is NULL and trigger oops
*) Dir entry block bh1 and bh2 belongs to one page, and the bh2 has already been unmapped.
For the metadata buffer we forgetting, we should always keep the mapped flag and clear the dirty flags is enough, so this patch pick out the these buffers and keep their BH_Mapped flag.
Link: https://lore.kernel.org/r/20200213063821.30455-3-yi.zhang@huawei.com Fixes: 904cdbd41d74 ("jbd2: clear dirty flag when revoking a buffer from an older transaction") Reviewed-by: Jan Kara jack@suse.cz Signed-off-by: zhangyi (F) yi.zhang@huawei.com Signed-off-by: Theodore Ts'o tytso@mit.edu Cc: stable@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/jbd2/commit.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-)
--- a/fs/jbd2/commit.c +++ b/fs/jbd2/commit.c @@ -982,12 +982,29 @@ restart_loop: * pagesize and it is attached to the last partial page. */ if (buffer_freed(bh) && !jh->b_next_transaction) { + struct address_space *mapping; + clear_buffer_freed(bh); clear_buffer_jbddirty(bh); - clear_buffer_mapped(bh); - clear_buffer_new(bh); - clear_buffer_req(bh); - bh->b_bdev = NULL; + + /* + * Block device buffers need to stay mapped all the + * time, so it is enough to clear buffer_jbddirty and + * buffer_freed bits. For the file mapping buffers (i.e. + * journalled data) we need to unmap buffer and clear + * more bits. We also need to be careful about the check + * because the data page mapping can get cleared under + * out hands, which alse need not to clear more bits + * because the page and buffers will be freed and can + * never be reused once we are done with them. + */ + mapping = READ_ONCE(bh->b_page->mapping); + if (mapping && !sb_is_blkdev_sb(mapping->host->i_sb)) { + clear_buffer_mapped(bh); + clear_buffer_new(bh); + clear_buffer_req(bh); + bh->b_bdev = NULL; + } }
if (buffer_jbddirty(bh)) {