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SubjectRe: [PATCH 1/1] fat: improve sync performance by grouping writes revised again
On Wed, 1 November 2006 11:17:50 -0500, Holden Karau wrote:
> + c_bh = kmalloc(nr_bhs*(sbi->fats) , GFP_KERNEL);
> + if (NULL == c_bh) {
> + printk(KERN_CRIT "not enough memory to store pointers to FAT blocks, will not sync. Possible data loss\n");
> + err = -ENOMEM;
> + goto error;
> + }

o I personally hate Yoda code ("Null the pointer is not, young Jedi").
o Old code simply returned -ENOMEM without printk. Assuming this was
sufficient before, the printk can be dropped.
o Some people prefer assigning err outside the condition. It is
supposed to give slightly better code on i386, iirc.

Result would be something like:
c_bh = kmalloc(...
err = -ENOMEM;
if (!c_bh)
goto error;
> + for (n = 0 ; n < nr_bhs ; n++ ) {
> + c_bh[(copy-1)*nr_bhs+n] = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
> + /* If there is not enough memory, fall back to the old system */
> + if (!c_bh[(copy-1)*nr_bhs+n]) {
> + printk("fat: not enough memory for all blocks , syncing at %d\n" ,(copy-1)*nr_bhs+n);

Whether this printk makes sense, I cannot tell.

> + fat_sync_bhs_optw( c_bh+i , (copy-1)*nr_bhs+n-i-1 , wait );
> + /* Free the now sync'd blocks */
> + for (; i < (copy-1)*nr_bhs+n ; i++)
> + brelse(c_bh[i]);
> + /* We try the same block again */
> + 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:not enough memory for block after existing blocks released. Possible data loss.\n");
> + err = -ENOMEM;
> + goto error;
> + }

As above.

> error:
> + if (NULL != c_bh) {
> + kfree(c_bh);
> + }

kfree(NULL) works just fine. You can remove the condition.

> +int fat_sync_bhs_optw(struct buffer_head **bhs, int nr_bhs ,int wait)
> {
> int i, err = 0;
>
> ll_rw_block(SWRITE, nr_bhs, bhs);
> - for (i = 0; i < nr_bhs; i++) {
> - wait_on_buffer(bhs[i]);
> - if (buffer_eopnotsupp(bhs[i])) {
> - clear_buffer_eopnotsupp(bhs[i]);
> - err = -EOPNOTSUPP;
> - } else if (!err && !buffer_uptodate(bhs[i]))
> - err = -EIO;
> + if (wait) {
> + for (i = 0; i < nr_bhs; i++) {
> + wait_on_buffer(bhs[i]);
> + if (buffer_eopnotsupp(bhs[i])) {
> + clear_buffer_eopnotsupp(bhs[i]);
> + err = -EOPNOTSUPP;
> + } else if (!err && !buffer_uptodate(bhs[i]))
> + err = -EIO;
> + }
> }
> +
> return err;
> }

You could keep the old indentation if your condition was changed to

if (!wait)
return 0;
Jörn

--
You can take my soul, but not my lack of enthusiasm.
-- Wally
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