I was thinking about the issue of running out of memory, while its not
particularly likely to happen except on devices with huge disks and
tiney amount of memory, it is a possibility. I can make it
fall-through to the previous way of doing things, does that sound like
a reasonable idea?
On 10/31/06, Holden Karau <holden@xxxxxxxxxxxxx> wrote:
On 10/31/06, Matthew Wilcox <matthew@xxxxxx> wrote:
> On Tue, Oct 31, 2006 at 10:03:08AM -0500, Holden Karau wrote:
> > @@ -343,52 +344,65 @@ int fat_ent_read(struct inode *inode, st
> > return ops->ent_get(fatent);
> > }
> >
> > -/* FIXME: We can write the blocks as more big chunk. */
> > -static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
> > - int nr_bhs)
> > +
> > +static int fat_mirror_bhs_optw(struct super_block *sb, struct buffer_head **bhs,
> > + int nr_bhs , int wait)
> > {
> > struct msdos_sb_info *sbi = MSDOS_SB(sb);
> > - struct buffer_head *c_bh;
> > + struct buffer_head *c_bh[nr_bhs*(sbi->fats)];
> > int err, n, copy;
> >
> > + /* Always wait if mounted -o sync */
> > + if (sb->s_flags & MS_SYNCHRONOUS )
> > + wait = 1;
> > err = 0;
> > for (copy = 1; copy < sbi->fats; copy++) {
> > sector_t backup_fat = sbi->fat_length * copy;
> > -
> > - for (n = 0; n < nr_bhs; n++) {
> > - c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
> > - if (!c_bh) {
> > + for (n = 0 ; n < nr_bhs ; n++ ) {
> > + c_bh[(copy-1)*nr_bhs+n] = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
> > + if (!c_bh[(copy-1)*nr_bhs+n]) {
> > + printk(KERN_CRIT "fat: out of memory while copying backup fat. possible data loss\n");
>
> I don't like that at all.
Not much to be done about that. The amount of memory required is
fairly small, but if its not there its not there.
>
> > err = -ENOMEM;
> > goto error;
> > }
> > - memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
> > - set_buffer_uptodate(c_bh);
> > - mark_buffer_dirty(c_bh);
> > - if (sb->s_flags & MS_SYNCHRONOUS)
> > - err = sync_dirty_buffer(c_bh);
> > - brelse(c_bh);
> > - if (err)
> > - goto error;
> > + memcpy(c_bh[(copy-1)*nr_bhs+n]->b_data, bhs[n]->b_data, sb->s_blocksize);
> > + set_buffer_uptodate(c_bh[(copy-1)*nr_bhs+n]);
> > + mark_buffer_dirty(c_bh[(copy-1)*nr_bhs+n]);
> > }
> > }
> > +
> > + if (wait) {
> > + for (n = 0 ; n < nr_bhs ; n++) {
> > + printk("copying to %d to %d\n" ,n, nr_bhs*(sbi->fats-1)+n);
>
> Is this the right version of the patch? The printk should never be left in.
> Plus, as far as I can tell, that whole loop is actually just memcpy().
whoops. That was in for debugging, I thought I took that out. The loop
structure is how it was before, but I don't see a way to get rid of
it, do you have an idea?
>
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