Jan Kara <[email protected]> writes:
> Hello,
Hello,
> I've noticed that extending a file using direct IO fails for FAT with
> EINVAL. It's basically because of the following code in fat_direct_IO():
>
> if (rw == WRITE) {
> /*
> * FIXME: blockdev_direct_IO() doesn't use
> * ->prepare_write(),
> * so we need to update the ->mmu_private to block
> * boundary.
> *
> * But we must fill the remaining area or hole by nul for
> * updating ->mmu_private.
> */
> loff_t size = offset + iov_length(iov, nr_segs);
> if (MSDOS_I(inode)->mmu_private < size)
> return -EINVAL;
> }
>
> But isn't this check bogus? blockdev_direct_IO writes only to space that
> is already allocated and stops as soon as it needs to extend the file
> (further extension is then handled by buffered writes). So it should
> already do what it needed for FAT. Thanks for an answer in advance.
FAT has to fill the hole completely, but DIO doesn't seems to do.
e.g.
fd = open("file", O_WRONLY | O_CREAT | O_TRUNC);
write(fd, buf, 512);
lseek(fd, 10000, SEEK_SET);
write(fd, buf, 512);
We need to allocate the blocks on 512 ~ 10000, and fill it with zero.
However, I think DIO doesn't fill it. If I'm missing something, please
let me know, I'll kill that check.
Thanks.
--
OGAWA Hirofumi <[email protected]>
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