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 <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 12d3fbc..cbfe13b 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2894,8 +2894,8 @@
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 @@
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)
@@ -4314,6 +4321,47 @@
}
/*
+ * 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()
*
* Called from notify_change.
@@ -4426,16 +4474,28 @@
}
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 cd4485d..ddc51a7 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -1840,7 +1840,6 @@
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 @@
* 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 @@
* @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 @@
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 @@
if (may_free && try_to_free_buffers(page))
J_ASSERT(!page_has_buffers(page));
}
+ return 0;
}
/*
