From 53e872681fed6a43047e71bf927f77d06f467988 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 25 Dec 2012 13:29:52 -0500 Subject: [PATCH] ext4: fix deadlock in journal_unmap_buffer() We cannot wait for transaction commit in journal_unmap_buffer() because we hold page lock which ranks below transaction start. We solve the issue by bailing out of journal_unmap_buffer() and jbd2_journal_invalidatepage() with -EBUSY. Caller is then responsible for waiting for transaction commit to finish and try invalidation again. Since the issue can happen only for page stradding i_size, it is simple enough to manually call jbd2_journal_invalidatepage() for such page from ext4_setattr(), check the return value and wait if necessary. Signed-off-by: Jan Kara Signed-off-by: "Theodore Ts'o" --- fs/ext4/inode.c | 82 +++++++++++++++++++++++++++++++++++++------ fs/jbd2/transaction.c | 27 +++++++------- include/linux/jbd2.h | 2 +- 3 files changed, 86 insertions(+), 25 deletions(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 12d3fbcff59f..cbfe13bf5b2a 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -2894,8 +2894,8 @@ static void ext4_invalidatepage(struct page *page, unsigned long offset) block_invalidatepage(page, offset); } -static void ext4_journalled_invalidatepage(struct page *page, - unsigned long offset) +static int __ext4_journalled_invalidatepage(struct page *page, + unsigned long offset) { journal_t *journal = EXT4_JOURNAL(page->mapping->host); @@ -2907,7 +2907,14 @@ static void ext4_journalled_invalidatepage(struct page *page, if (offset == 0) ClearPageChecked(page); - jbd2_journal_invalidatepage(journal, page, offset); + return jbd2_journal_invalidatepage(journal, page, offset); +} + +/* Wrapper for aops... */ +static void ext4_journalled_invalidatepage(struct page *page, + unsigned long offset) +{ + WARN_ON(__ext4_journalled_invalidatepage(page, offset) < 0); } static int ext4_releasepage(struct page *page, gfp_t wait) @@ -4313,6 +4320,47 @@ int ext4_write_inode(struct inode *inode, struct writeback_control *wbc) return err; } +/* + * In data=journal mode ext4_journalled_invalidatepage() may fail to invalidate + * buffers that are attached to a page stradding i_size and are undergoing + * commit. In that case we have to wait for commit to finish and try again. + */ +static void ext4_wait_for_tail_page_commit(struct inode *inode) +{ + struct page *page; + unsigned offset; + journal_t *journal = EXT4_SB(inode->i_sb)->s_journal; + tid_t commit_tid = 0; + int ret; + + offset = inode->i_size & (PAGE_CACHE_SIZE - 1); + /* + * All buffers in the last page remain valid? Then there's nothing to + * do. We do the check mainly to optimize the common PAGE_CACHE_SIZE == + * blocksize case + */ + if (offset > PAGE_CACHE_SIZE - (1 << inode->i_blkbits)) + return; + while (1) { + page = find_lock_page(inode->i_mapping, + inode->i_size >> PAGE_CACHE_SHIFT); + if (!page) + return; + ret = __ext4_journalled_invalidatepage(page, offset); + unlock_page(page); + page_cache_release(page); + if (ret != -EBUSY) + return; + commit_tid = 0; + read_lock(&journal->j_state_lock); + if (journal->j_committing_transaction) + commit_tid = journal->j_committing_transaction->t_tid; + read_unlock(&journal->j_state_lock); + if (commit_tid) + jbd2_log_wait_commit(journal, commit_tid); + } +} + /* * ext4_setattr() * @@ -4426,16 +4474,28 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr) } if (attr->ia_valid & ATTR_SIZE) { - if (attr->ia_size != i_size_read(inode)) { - truncate_setsize(inode, attr->ia_size); - /* Inode size will be reduced, wait for dio in flight. - * Temporarily disable dioread_nolock to prevent - * livelock. */ + if (attr->ia_size != inode->i_size) { + loff_t oldsize = inode->i_size; + + i_size_write(inode, attr->ia_size); + /* + * Blocks are going to be removed from the inode. Wait + * for dio in flight. Temporarily disable + * dioread_nolock to prevent livelock. + */ if (orphan) { - ext4_inode_block_unlocked_dio(inode); - inode_dio_wait(inode); - ext4_inode_resume_unlocked_dio(inode); + if (!ext4_should_journal_data(inode)) { + ext4_inode_block_unlocked_dio(inode); + inode_dio_wait(inode); + ext4_inode_resume_unlocked_dio(inode); + } else + ext4_wait_for_tail_page_commit(inode); } + /* + * Truncate pagecache after we've waited for commit + * in data=journal mode to make pages freeable. + */ + truncate_pagecache(inode, oldsize, inode->i_size); } ext4_truncate(inode); } diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c index cd4485db42b3..ddc51a7f4508 100644 --- a/fs/jbd2/transaction.c +++ b/fs/jbd2/transaction.c @@ -1840,7 +1840,6 @@ static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh, BUFFER_TRACE(bh, "entry"); -retry: /* * It is safe to proceed here without the j_list_lock because the * buffers cannot be stolen by try_to_free_buffers as long as we are @@ -1935,14 +1934,11 @@ static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh, * for commit and try again. */ if (partial_page) { - tid_t tid = journal->j_committing_transaction->t_tid; - jbd2_journal_put_journal_head(jh); spin_unlock(&journal->j_list_lock); jbd_unlock_bh_state(bh); write_unlock(&journal->j_state_lock); - jbd2_log_wait_commit(journal, tid); - goto retry; + return -EBUSY; } /* * OK, buffer won't be reachable after truncate. We just set @@ -2003,21 +1999,23 @@ static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh, * @page: page to flush * @offset: length of page to invalidate. * - * Reap page buffers containing data after offset in page. - * + * Reap page buffers containing data after offset in page. Can return -EBUSY + * if buffers are part of the committing transaction and the page is straddling + * i_size. Caller then has to wait for current commit and try again. */ -void jbd2_journal_invalidatepage(journal_t *journal, - struct page *page, - unsigned long offset) +int jbd2_journal_invalidatepage(journal_t *journal, + struct page *page, + unsigned long offset) { struct buffer_head *head, *bh, *next; unsigned int curr_off = 0; int may_free = 1; + int ret = 0; if (!PageLocked(page)) BUG(); if (!page_has_buffers(page)) - return; + return 0; /* We will potentially be playing with lists other than just the * data lists (especially for journaled data mode), so be @@ -2031,9 +2029,11 @@ void jbd2_journal_invalidatepage(journal_t *journal, if (offset <= curr_off) { /* This block is wholly outside the truncation point */ lock_buffer(bh); - may_free &= journal_unmap_buffer(journal, bh, - offset > 0); + ret = journal_unmap_buffer(journal, bh, offset > 0); unlock_buffer(bh); + if (ret < 0) + return ret; + may_free &= ret; } curr_off = next_off; bh = next; @@ -2044,6 +2044,7 @@ void jbd2_journal_invalidatepage(journal_t *journal, if (may_free && try_to_free_buffers(page)) J_ASSERT(!page_has_buffers(page)); } + return 0; } /* diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h index 1be23d9fdacb..e30b66346942 100644 --- a/include/linux/jbd2.h +++ b/include/linux/jbd2.h @@ -1098,7 +1098,7 @@ void jbd2_journal_set_triggers(struct buffer_head *, extern int jbd2_journal_dirty_metadata (handle_t *, struct buffer_head *); extern int jbd2_journal_forget (handle_t *, struct buffer_head *); extern void journal_sync_buffer (struct buffer_head *); -extern void jbd2_journal_invalidatepage(journal_t *, +extern int jbd2_journal_invalidatepage(journal_t *, struct page *, unsigned long); extern int jbd2_journal_try_to_free_buffers(journal_t *, struct page *, gfp_t); extern int jbd2_journal_stop(handle_t *); -- GitLab