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ext4: fix delalloc i_disksize early update issue 

Ext4_da_write_end() used walk_page_buffers() with a callback function of
ext4_bh_unmapped_or_delay() to check if it extended the file size
without allocating any blocks (since in this case i_disksize needs to be
updated).  However, this is didn't work proprely because the buffer head
has not been marked dirty yet --- this is done later in
block_commit_write() --- which caused ext4_bh_unmapped_or_delay() to
always return false.

In addition, walk_page_buffers() checks all of the buffer heads covering
the page, and the only buffer_head that should be checked is the one
covering the end of the write.  Otherwise, given a 1k blocksize
filesystem and a 4k page size, the buffer head covering the first 1k
stripe of the file could be unmapped (because it was a sparse file), and
the second or third buffer_head covering that page could be mapped, and
using walk_page_buffers() would fail in this case since it would stop at
the first unmapped buffer_head and return true.

The core problem is that walk_page_buffers() was intended to do work in
a callback function, and a non-zero return value indicated a failure,
which termined the walk of the buffer heads covering the page.  It was
not intended to be used with a boolean function, such as
ext4_bh_unmapped_or_delay().

Add addtional fix from Aneesh to protect i_disksize update rave with truncate.

Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Mingming Cao 2008-07-11 19:27:31 -04:00 committed by Theodore Ts'o
parent f0e6c98593
commit 632eaeab1f
1 changed files with 47 additions and 16 deletions
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63
fs/ext4/inode.c
View File

@ -2298,6 +2298,29 @@ out:
return ret;
}
/*
* Check if we should update i_disksize
* when write to the end of file but not require block allocation
*/
static int ext4_da_should_update_i_disksize(struct page *page,
unsigned long offset)
{
struct buffer_head *bh;
struct inode *inode = page->mapping->host;
unsigned int idx;
int i;
bh = page_buffers(page);
idx = offset >> inode->i_blkbits;
for (i=0; i < idx; i++)
bh = bh->b_this_page;
if (!buffer_mapped(bh) || (buffer_delay(bh)))
return 0;
return 1;
}
static int ext4_da_write_end(struct file *file,
struct address_space *mapping,
loff_t pos, unsigned len, unsigned copied,
@ -2307,6 +2330,10 @@ static int ext4_da_write_end(struct file *file,
int ret = 0, ret2;
handle_t *handle = ext4_journal_current_handle();
loff_t new_i_size;
unsigned long start, end;
start = pos & (PAGE_CACHE_SIZE - 1);
end = start + copied -1;
/*
* generic_write_end() will run mark_inode_dirty() if i_size
@ -2315,18 +2342,23 @@ static int ext4_da_write_end(struct file *file,
*/
new_i_size = pos + copied;
if (new_i_size > EXT4_I(inode)->i_disksize)
if (!walk_page_buffers(NULL, page_buffers(page),
0, len, NULL, ext4_bh_unmapped_or_delay)){
/*
* Updating i_disksize when extending file without
* needing block allocation
*/
if (ext4_should_order_data(inode))
ret = ext4_jbd2_file_inode(handle, inode);
if (new_i_size > EXT4_I(inode)->i_disksize) {
if (ext4_da_should_update_i_disksize(page, end)) {
down_write(&EXT4_I(inode)->i_data_sem);
if (new_i_size > EXT4_I(inode)->i_disksize) {
/*
* Updating i_disksize when extending file
* without needing block allocation
*/
if (ext4_should_order_data(inode))
ret = ext4_jbd2_file_inode(handle,
inode);
EXT4_I(inode)->i_disksize = new_i_size;
EXT4_I(inode)->i_disksize = new_i_size;
}
up_write(&EXT4_I(inode)->i_data_sem);
}
}
ret2 = generic_write_end(file, mapping, pos, len, copied,
page, fsdata);
copied = ret2;
@ -3393,6 +3425,11 @@ void ext4_truncate(struct inode *inode)
if (ext4_orphan_add(handle, inode))
goto out_stop;
/*
* From here we block out all ext4_get_block() callers who want to
* modify the block allocation tree.
*/
down_write(&ei->i_data_sem);
/*
* The orphan list entry will now protect us from any crash which
* occurs before the truncate completes, so it is now safe to propagate
@ -3402,12 +3439,6 @@ void ext4_truncate(struct inode *inode)
*/
ei->i_disksize = inode->i_size;
/*
* From here we block out all ext4_get_block() callers who want to
* modify the block allocation tree.
*/
down_write(&ei->i_data_sem);
if (n == 1) { /* direct blocks */
ext4_free_data(handle, inode, NULL, i_data+offsets[0],
i_data + EXT4_NDIR_BLOCKS);