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Re: [PATCH] Don't look for a partition map on a floppy
From: |
Vladimir 'φ-coder/phcoder' Serbinenko |
Subject: |
Re: [PATCH] Don't look for a partition map on a floppy |
Date: |
Fri, 15 Jun 2012 07:15:16 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:10.0.4) Gecko/20120510 Icedove/10.0.4 |
On 15.06.2012 07:10, Robert Mabee wrote:
> "echo *" takes about 12 seconds on my system (PC, BIOS, empty floppy drive)
> because grub_partition_iterate tries to enumerate the partitions on the
> floppy.
> "search --no-floppy" probably hits the same delay (not verified) since
> it has to
> generate the partition names before it can discard fd[0-9].
>
search -s stops when it finds first matching device and floppies are
checked in the last place.
> I suggest skipping tiny devices (ie < 4 MB) rather than looking at the name
> so it won't affect various 100 MB super floppies that might appear as BIOS
> floppies and therefore get indistinguishable names in fd[0-9]. Arguably
> these drives should continue to support partition maps, at the expense of
> long timeouts if they don't handle missing media any better than plain-old
> floppy drives do.
Minix floppies are partitioned.
>
> === modified file 'ChangeLog'
> --- old/ChangeLog 2012-06-09 17:58:38 +0000
> +++ new/ChangeLog 2012-06-15 04:34:50 +0000
> @@ -1,3 +1,15 @@
> +2012-06-15 Bob Mabee <address@hidden>
> +
> + * kern/partition.c (grub_partition_is_plausible): New function to
> + decide drive is too small (like floppy) to support partitioning.
> + * (grub_partition_iterate): Use above so search and (*) avoid long
> + timeouts trying to read partmap from a missing floppy.
> +
> 2012-06-09 Vladimir Serbinenko <address@hidden>
>
> * tests/grub_script_expansion.in: Explicitly tell grep that we handle
>
> === modified file 'grub-core/kern/partition.c'
> --- old/grub-core/kern/partition.c 2012-02-08 19:19:44 +0000
> +++ new/grub-core/kern/partition.c 2012-06-14 05:30:02 +0000
> @@ -162,12 +162,23 @@
> return part;
> }
>
> +/* Very unlikely to find a partmap on a tiny floppy, but looking for a
> + map costs a long timeout if drive is empty, so skip device < 4 MB.
> + (Allowing for a lower-overhead format on biggest media, 2.88 MB.) */
> +static int
> +grub_partition_is_plausible (struct grub_disk *disk)
> +{
> + grub_uint64_t n_bytes = grub_disk_get_size (disk) <<
> GRUB_DISK_SECTOR_BITS;
> + return n_bytes >= 4 << 20;
> +}
> +
> int
> grub_partition_iterate (struct grub_disk *disk,
> int (*hook) (grub_disk_t disk,
> const grub_partition_t partition))
> {
> int ret = 0;
> + if (!grub_partition_is_plausible (disk)) return ret;
>
> auto int part_iterate (grub_disk_t dsk, const grub_partition_t p);
>
>
>
>
> _______________________________________________
> Grub-devel mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/grub-devel
>
--
Regards
Vladimir 'φ-coder/phcoder' Serbinenko
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