[PATCH 47/49] ext4: Avoid leaking blocks after a block allocation failure

Theodore Ts'o
2009-06-08T19:31:35Z

From: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

We should add inode to the orphan list in the same transaction
as block allocation. This ensures that if we crash after a failed
block allocation and before we do a vmtruncate we don't leak block
(ie block marked as used in bitmap but not claimed by the inode).

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
CC: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
fs/ext4/inode.c | 24 ++++++++++++++++++++++--
1 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 95a3f45..036552a 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1462,7 +1462,7 @@ static int ext4_write_begin(struct file *file, struct address_space *mapping,
struct page **pagep, void **fsdata)
{
struct inode *inode = mapping->host;
- int ret, needed_blocks = ext4_writepage_trans_blocks(inode);
+ int ret, needed_blocks;
handle_t *handle;
int retries = 0;
struct page *page;
@@ -1473,6 +1473,11 @@ static int ext4_write_begin(struct file *file, struct address_space *mapping,
"dev %s ino %lu pos %llu len %u flags %u",
inode->i_sb->s_id, inode->i_ino,
(unsigned long long) pos, len, flags);
+ /*
+ * Reserve one block more for addition to orphan list in case
+ * we allocate blocks but write fails for some reason
+ */
+ needed_blocks = ext4_writepage_trans_blocks(inode) + 1;
index = pos >> PAGE_CACHE_SHIFT;
from = pos & (PAGE_CACHE_SIZE - 1);
to = from + len;
@@ -1506,15 +1511,30 @@ retry:

if (ret) {
unlock_page(page);
- ext4_journal_stop(handle);
page_cache_release(page);
/*
* block_write_begin may have instantiated a few blocks
* outside i_size. Trim these off again. Don't need
* i_size_read because we hold i_mutex.
+ *
+ * Add inode to orphan list in case we crash before
+ * truncate finishes
*/
if (pos + len > inode->i_size)
+ ext4_orphan_add(handle, inode);
+
+ ext4_journal_stop(handle);
+ if (pos + len > inode->i_size) {
vmtruncate(inode, inode->i_size);
+ /*
+ * If vmtruncate failed early the inode might
+ * still be on the orphan list; we need to
+ * make sure the inode is removed from the
+ * orphan list in that case.
+ */
+ if (inode->i_nlink)
+ ext4_orphan_del(NULL, inode);
+ }
}

if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
--
1.6.3.2.1.gb9f7d.dirty