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ext4: fix deadlock in journal_unmap_buffer()

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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>
This commit is contained in:
Jan Kara
2012-12-25 13:29:52 -05:00
committed by Theodore Ts'o
parent 4520fb3c36
commit 53e872681f
3 changed files with 86 additions and 25 deletions
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82
fs/ext4/inode.c
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@@ -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);
}