Ext4: fix delalloc i_disksize early update issue From: Mingming Cao Ext4_da_write_end() uses ext4_bh_unmapped_or_delay() function to check if it extend the file size without need for allocation. But at that time the buffer has not being dirtied yet (done in code later in block_commit_write()), so it always return true and update i_disksize (before block allocation). we could fix that ext4_da_write_end() to not use this helper function. This also fixed another issue: The i_disksize is updated at ext4_da_write_end() time if writes to the end of file, and the buffers are all have blocks allocated. But if the page had one buffer marked as buffer_delay, and the write is at EOF and on a buffer has block already allocated, we certainly need to extend the i_disksize. Signed-off-by: Mingming Cao --- fs/ext4/inode.c | 32 ++++++++++++++++++++++++++++++-- 1 file changed, 30 insertions(+), 2 deletions(-) Index: linux-2.6.26-rc8/fs/ext4/inode.c =================================================================== --- linux-2.6.26-rc8.orig/fs/ext4/inode.c 2008-07-02 09:53:42.000000000 -0700 +++ linux-2.6.26-rc8/fs/ext4/inode.c 2008-07-02 10:01:09.000000000 -0700 @@ -1891,6 +1891,30 @@ 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 *head, *bh; + unsigned int curr_off = 0; + + head = page_buffers(page); + bh = head; + do { + unsigned int next_off = curr_off + bh->b_size; + + if (curr_off >= offset && + (!buffer_mapped(bh) || (buffer_delay(bh)))) + return 0; + curr_off = next_off; + } while ((bh = bh->b_this_page) != head); + + return 1; +} + static int ext4_da_write_end(struct file *file, struct address_space *mapping, loff_t pos, unsigned len, unsigned copied, @@ -1900,6 +1924,10 @@ static int ext4_da_write_end(struct 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; /* * generic_write_end() will run mark_inode_dirty() if i_size @@ -1909,8 +1937,7 @@ static int ext4_da_write_end(struct 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)){ + if (ext4_da_should_update_i_disksize(page, end)) { /* * Updating i_disksize when extending file without * need block allocation