Re: [PATCH v3] fat: editions to support fat_fallocate

OGAWA Hirofumi
2013-03-09T14:18:12Z

Namjae Jeon <linkinjeon@gmail.com> writes:

> static int fat_file_release(struct inode *inode, struct file *filp)
> {
> + struct super_block *sb = inode->i_sb;
> + loff_t mmu_private_ideal = (inode->i_size + (sb->s_blocksize-1)) &
> + ~(sb->s_blocksize-1);
> + if (mmu_private_ideal < MSDOS_I(inode)->mmu_private &&
> + filp->f_dentry->d_count == 1)
> + fat_truncate_blocks(inode, inode->i_size);

Without locking, truncate is racy.

This choose ->release(). BTW, we would also be able to do this only
->evict_inode(), although I'm not thinking yet which one is better.

If you had conclusion, it would be nice to explain it.

> +static long fat_fallocate(struct file *file, int mode,
> + loff_t offset, loff_t len)
> +{
>
> + if ((offset + len) <= MSDOS_I(inode)->mmu_private) {
> + fat_msg(sb, KERN_ERR,
> + "fat_fallocate():Blocks already allocated");
> + return -EINVAL;
> + }

Also this looks like totally racy.

> static int fat_write_begin(struct file *file, struct address_space *mapping,
> loff_t pos, unsigned len, unsigned flags,
> struct page **pagep, void **fsdata)
> {
> int err;
> + struct inode *inode = mapping->host;
> + struct super_block *sb = inode->i_sb;
> + loff_t mmu_private_actual = MSDOS_I(inode)->mmu_private;
> + loff_t mmu_private_ideal = (inode->i_size + (sb->s_blocksize-1)) &
> + ~(sb->s_blocksize-1);
> +
> + if ((mmu_private_actual > mmu_private_ideal) && (pos > inode->i_size)) {
> + err = fat_zero_falloc_area(file, mapping, pos);
> + if (err)
> + fat_msg(sb, KERN_ERR, "error zeroing fallocated area");
> + }
>
> *pagep = NULL;
> err = cont_write_begin(file, mapping, pos, len, flags,

Hm, only write_begin is enough to handle mmap, truncate, and etc.?

Thanks.
--
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>