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ext4: Avoid data / filesystem corruption when write fails to copy data

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When ext4_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 the 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.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Jan Kara 2009-12-08 21:24:33 -05:00 committed by Theodore Ts'o
parent 24b584240a
commit b9a4207d5e
1 changed files with 15 additions and 5 deletions
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20
fs/ext4/inode.c
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@ -1492,6 +1492,16 @@ static int do_journal_get_write_access(handle_t *handle,
return ext4_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 ext4_truncate_failed_write(struct inode *inode)
{
truncate_inode_pages(inode->i_mapping, inode->i_size);
ext4_truncate(inode);
}
static int ext4_write_begin(struct file *file, struct address_space *mapping,
loff_t pos, unsigned len, unsigned flags,
struct page **pagep, void **fsdata)
@ -1557,7 +1567,7 @@ retry:
ext4_journal_stop(handle);
if (pos + len > inode->i_size) {
ext4_truncate(inode);
ext4_truncate_failed_write(inode);
/*
* If truncate failed early the inode might
* still be on the orphan list; we need to
@ -1667,7 +1677,7 @@ static int ext4_ordered_write_end(struct file *file,
ret = ret2;
if (pos + len > inode->i_size) {
ext4_truncate(inode);
ext4_truncate_failed_write(inode);
/*
* If truncate failed early the inode might still be
* on the orphan list; we need to make sure the inode
@ -1709,7 +1719,7 @@ static int ext4_writeback_write_end(struct file *file,
ret = ret2;
if (pos + len > inode->i_size) {
ext4_truncate(inode);
ext4_truncate_failed_write(inode);
/*
* If truncate failed early the inode might still be
* on the orphan list; we need to make sure the inode
@ -1772,7 +1782,7 @@ static int ext4_journalled_write_end(struct file *file,
if (!ret)
ret = ret2;
if (pos + len > inode->i_size) {
ext4_truncate(inode);
ext4_truncate_failed_write(inode);
/*
* If truncate failed early the inode might still be
* on the orphan list; we need to make sure the inode
@ -3048,7 +3058,7 @@ retry:
* i_size_read because we hold i_mutex.
*/
if (pos + len > inode->i_size)
ext4_truncate(inode);
ext4_truncate_failed_write(inode);
}
if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))