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Subject[PATCH] Re: [bug] infinite loop in generic_make_request()
On Thursday November 30, ganesh@veritas.com wrote:
> [cc'ed to maintainers of md and lvm]
>
> hi,
> in generic_make_request(), the following code handles stacking:
>
> do {
> q = blk_get_queue(bh->b_rdev);
> if (!q) {
> printk(...)
> buffer_IO_error(bh);
> break;
> }
> } while (q->make_request_fn(q, rw, bh));
>
> however, make_request_fn may return -1 in case of errors. one such fn is
> raid0_make_request(). this causes generic_make_request() to loop endlessly.
> lvm returns 1 unconditionally, so it would also loop if an error occured in
> lvm_map(). other bdevs might have the same problem.
> I think a better mechanism would be to mandate that make_request_fn ought
> to call bh->b_end_io() in case of errors and return 0.
>
> ganesh

Good catch, thanks. Below is a patch to fix md drivers (md.c,
linear.c and raid0.c).

NeilBrown



--- ./drivers/md/md.c 2000/11/30 08:23:51 1.2
+++ ./drivers/md/md.c 2000/11/30 09:20:05 1.3
@@ -179,7 +179,7 @@
return mddev->pers->make_request(mddev, rw, bh);
else {
buffer_IO_error(bh);
- return -1;
+ return 0;
}
}

--- ./drivers/md/linear.c 2000/11/30 08:23:51 1.2
+++ ./drivers/md/linear.c 2000/11/30 09:20:05 1.3
@@ -136,7 +136,8 @@
if (!hash->dev1) {
printk ("linear_make_request : hash->dev1==NULL for block %ld\n",
block);
- return -1;
+ buffer_IO_error(bh);
+ return 0;
}
tmp_dev = hash->dev1;
} else
@@ -145,7 +146,8 @@
if (block >= (tmp_dev->size + tmp_dev->offset)
|| block < tmp_dev->offset) {
printk ("linear_make_request: Block %ld out of bounds on dev %s size %ld offset %ld\n", block, kdevname(tmp_dev->dev), tmp_dev->size, tmp_dev->offset);
- return -1;
+ buffer_IO_error(bh);
+ return 0;
}
bh->b_rdev = tmp_dev->dev;
bh->b_rsector = bh->b_rsector - (tmp_dev->offset << 1);
--- ./drivers/md/raid0.c 2000/11/30 08:23:51 1.2
+++ ./drivers/md/raid0.c 2000/11/30 09:20:05 1.3
@@ -275,16 +275,18 @@

bad_map:
printk ("raid0_make_request bug: can't convert block across chunks or bigger than %dk %ld %d\n", chunk_size, bh->b_rsector, bh->b_size >> 10);
- return -1;
+ goto outerr;
bad_hash:
printk("raid0_make_request bug: hash==NULL for block %ld\n", block);
- return -1;
+ goto outerr;
bad_zone0:
printk ("raid0_make_request bug: hash->zone0==NULL for block %ld\n", block);
- return -1;
+ goto outerr;
bad_zone1:
printk ("raid0_make_request bug: hash->zone1==NULL for block %ld\n", block);
- return -1;
+ outerr:
+ buffer_IO_error(bh);
+ return 0;
}

static int raid0_status (char *page, mddev_t *mddev)
-
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