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BTW, I want send another patch as follows: diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index bf0b7dea4900..570a687ae847 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3149,7 +3149,7 @@ static int ext4_da_write_end(struct file *file, return ext4_write_inline_data_end(inode, pos, len, copied, page); start = pos & (PAGE_SIZE - 1); - end = start + copied - 1; + end = start + (copied ? copied - 1 : copied); /* * Since we are holding inode lock, we are sure i_disksize <= @@ -3167,7 +3167,7 @@ static int ext4_da_write_end(struct file *file, * ext4_da_write_inline_data_end(). */ new_i_size = pos + copied; - if (copied && new_i_size > inode->i_size && + if (new_i_size > inode->i_size && ext4_da_should_update_i_disksize(page, end)) ext4_update_i_disksize(inode, new_i_size); This modification handle unconsistent i_size and i_disksize imported by ea51d132dbf9 ("ext4: avoid hangs in ext4_da_should_update_i_disksize()"). Paritially written may display a fake inode size for user, for example: i_disksize=1 generic_perform_write copied = iov_iter_copy_from_user_atomic(len) // copied = 0 ext4_da_write_end // skip updating i_disksize generic_write_end if (pos + copied > inode->i_size) { // 10 + 0 > 1, true i_size_write(inode, pos + copied); // i_size = 10 } 0 1 10 4096 |_|_______|_________..._____| | | i_size pos Now, user see the i_size is 10 (i_disksize is still 1). After inode destroyed, user will get the i_size is 1 read from disk.OK, but shouldn't we rather change generic_write_end() to not increase i_size if no write happened? Because that is what seems somewhat problematic... Honza
After looking through some code, I find some other places have similar problem:
1. In ext4_write_end(), i_size is updated by ext4 not generic_write_end(). 2. The iommap framework, i_size is updated even copied is zero. 3. ubifs_write_end, i_size is updated even copied is zero. It seems that fixing all places is not an easy work.
