Re: waiting 10s before mounting root filesystem?

From: Jesper Juhl (juhl-lkml_at_dif.dk)
Date: 12/31/04

  • Next message: Coywolf Qi Hunt: "Re: Linux 2.6.10-ac2" 
    Date:	Fri, 31 Dec 2004 02:45:53 +0100 (CET)
To: William Park <opengeometry@yahoo.ca>

    William Park wrote:
    > On Thu, Dec 30, 2004 at 01:25:32PM -0200, Marcelo Tosatti wrote:
    > > On Tue, Dec 28, 2004 at 07:59:22PM -0500, William Park wrote:
    > > > On Mon, Dec 27, 2004 at 10:23:34PM +0100, Andreas Unterkircher wrote:
    > > > > [1] http://www.xenotime.net/linux/usb/usbboot-2422.patch
    > > >
    > > > Thanks Andreas. I can now boot from my el-cheapo USB key drive
    > > > (256MB SanDisk Cruzer Mini). Since mine takes about 5sec to show
    > > > up, I decided to wait 5sec instead of 1sec. Here is diff for
    > > > 2.6.10:
    > > >
    > > > --- ./init/do_mounts.c--orig 2004-12-27 17:36:35.000000000 -0500
    > > > +++ ./init/do_mounts.c 2004-12-28 17:27:26.000000000 -0500
    > > > @@ -301,7 +301,14 @@ retry:
    > > > root_device_name, b);
    > > > printk("Please append a correct \"root=\" boot option\n");
    > > >
    > > > +#if 0 /* original code */
    > > > panic("VFS: Unable to mount root fs on %s", b);
    > > > +#else
    > > > + printk ("Waiting 5 seconds to try again...\n");
    > > > + set_current_state(TASK_INTERRUPTIBLE);
    > > > + schedule_timeout(5 * HZ);
    > > > + goto retry;
    > > > +#endif
    > > > }
    > > > panic("VFS: Unable to mount root fs on %s", __bdevname(ROOT_DEV, b));
    > > > out:
    > >
    > > William,
    > >
    > > Solar version which is now merged in v2.4 looks better (5s sleep is
    > > too long and only one try) IMO.
    > >
    > > It sleeps 1s each time, 10 times. More reliable and faster.
    > >
    > >
    > http://linux.bkbits.net:8080/linux-2.4/patch@1.1527.1.20?nav=index.html|ChangeSet@-3w|cset@1.1527.1.20
    >
    > Hi Marcelo,
    >
    > 1. Actually, my patch above loops every 5s to reduce screen clutter,
    > whereas the original 2.4 patch (cited by Andreas Unterkircher) loops
    > every 1s. Both loops forever.
    >
    > But, if a limit of 10 tries is what you want, then here is a patch
    > for 2.6.10:

    I agree with you that reducing screen clutter is a good thing. How about
    something like this that waits for 10+ seconds so even slow devices have a
    chance to get up but also does some primitive ratelimiting on the messages
    by only printing one every 3 seconds (but still attempting to mount every
    1 sec) ?

    This is a small variation on the patch I posted a little while ago.

    Signed-off-by: Jesper Juhl <juhl-lkml@dif.dk>

    diff -up linux-2.6.10-bk2-orig/init/do_mounts.c linux-2.6.10-bk2/init/do_mounts.c
    --- linux-2.6.10-bk2-orig/init/do_mounts.c 2004-12-24 22:34:31.000000000 +0100
    +++ linux-2.6.10-bk2/init/do_mounts.c 2004-12-31 02:44:13.000000000 +0100
    @@ -6,6 +6,7 @@
     #include <linux/suspend.h>
     #include <linux/root_dev.h>
     #include <linux/security.h>
    +#include <linux/delay.h>
     
     #include <linux/nfs_fs.h>
     #include <linux/nfs_fs_sb.h>
    @@ -278,6 +279,7 @@ void __init mount_block_root(char *name,
             char *fs_names = __getname();
             char *p;
             char b[BDEVNAME_SIZE];
    + short retries = 15;
     
             get_fs_names(fs_names);
     retry:
    @@ -297,9 +299,17 @@ retry:
                      * and bad superblock on root device.
                      */
                     __bdevname(ROOT_DEV, b);
    - printk("VFS: Cannot open root device \"%s\" or %s\n",
    + if (retries--) {
    + if (retries % 3 == 0)
    + printk(KERN_WARNING "VFS: Cannot open root device "
    + "\"%s\" or %s, retrying in 1s.\n",
    + root_device_name, b);
    + ssleep(1);
    + goto retry;
    + }
    + printk(KERN_CRIT "VFS: Cannot open root device \"%s\" or %s, giving up.\n",
                                     root_device_name, b);
    - printk("Please append a correct \"root=\" boot option\n");
    + printk(KERN_CRIT "Please append a correct \"root=\" boot option\n");
     
                     panic("VFS: Unable to mount root fs on %s", b);
             }

    >
    > 2. I sincerely hope that this patch get included in the main kernel.
    > USB boot is very important feature, and will become the standard way
    > of booting Linux thin-client as well as other Linux system, embedded
    > or not. It will make Netboot, Etherboot, PXE boot, CF-to-IDE
    > adapter, and initrd all obsolete.
    >
    I agree, some version of this should go into 2.6. If we can successfully
    get the system up and running by retrying the root fs mount a few times
    then that's a lot better than panicking :) 

    -- 
Jesper Juhl
PS. Sorry if I messed up the thread a bit, but I had some mailserver 
trouble and lost a few LKML mails so I couldn't reply directly to the 
proper mail.
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