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Subject[81/90] ext3: Fix data / filesystem corruption when write fails to copy data
2.6.31-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Jan Kara <jack@suse.cz>

commit 68eb3db08344286733adac48304d9fb7a0e53b27 upstream.

When ext3_write_begin fails after allocating some blocks or
generic_perform_write fails to copy data to write, we truncate blocks already
instantiated beyond i_size. Although these blocks were never inside i_size, we
have to truncate pagecache of these blocks so that corresponding buffers get
unmapped. Otherwise subsequent __block_prepare_write (called because we are
retrying the write) will find the buffers mapped, not call ->get_block, and
thus the page will be backed by already freed blocks leading to filesystem and
data corruption.

Reported-by: James Y Knight <foom@fuhm.net>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/ext3/inode.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
--- a/fs/ext3/inode.c
+++ b/fs/ext3/inode.c
@@ -1137,6 +1137,16 @@ static int do_journal_get_write_access(h
return ext3_journal_get_write_access(handle, bh);
}

+/*
+ * Truncate blocks that were not used by write. We have to truncate the
+ * pagecache as well so that corresponding buffers get properly unmapped.
+ */
+static void ext3_truncate_failed_write(struct inode *inode)
+{
+ truncate_inode_pages(inode->i_mapping, inode->i_size);
+ ext3_truncate(inode);
+}
+
static int ext3_write_begin(struct file *file, struct address_space *mapping,
loff_t pos, unsigned len, unsigned flags,
struct page **pagep, void **fsdata)
@@ -1195,7 +1205,7 @@ write_begin_failed:
unlock_page(page);
page_cache_release(page);
if (pos + len > inode->i_size)
- ext3_truncate(inode);
+ ext3_truncate_failed_write(inode);
}
if (ret == -ENOSPC && ext3_should_retry_alloc(inode->i_sb, &retries))
goto retry;
@@ -1290,7 +1300,7 @@ static int ext3_ordered_write_end(struct
page_cache_release(page);

if (pos + len > inode->i_size)
- ext3_truncate(inode);
+ ext3_truncate_failed_write(inode);
return ret ? ret : copied;
}

@@ -1316,7 +1326,7 @@ static int ext3_writeback_write_end(stru
page_cache_release(page);

if (pos + len > inode->i_size)
- ext3_truncate(inode);
+ ext3_truncate_failed_write(inode);
return ret ? ret : copied;
}

@@ -1369,7 +1379,7 @@ static int ext3_journalled_write_end(str
page_cache_release(page);

if (pos + len > inode->i_size)
- ext3_truncate(inode);
+ ext3_truncate_failed_write(inode);
return ret ? ret : copied;
}




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