From: Andrew Morton <akpm@linux-foundation.org>
To: Will Drewry <wad@chromium.org>
Cc: linux-kernel@vger.kernel.org, kay.sievers@vrfy.org,
Jens Axboe <jaxboe@fusionio.com>,
Namhyung Kim <namhyung@gmail.com>,
Trond Myklebust <Trond.Myklebust@netapp.com>
Subject: Re: [PATCH v3 1/2] init: add root=PARTUUID=UUID/PARTNROFF=%d support
Date: Tue, 5 Jul 2011 13:53:48 -0700 [thread overview]
Message-ID: <20110705135348.cb835073.akpm@linux-foundation.org> (raw)
In-Reply-To: <1309468207-24199-1-git-send-email-wad@chromium.org>
On Thu, 30 Jun 2011 16:10:06 -0500
Will Drewry <wad@chromium.org> wrote:
> Expand root=PARTUUID=UUID syntax to support selecting a root partition
> by integer offset from a known, unique partition. This approach
> provides similar properties to specifying a device and partition number,
> but using the UUID as the unique path prior to evaluating the offset.
>
> For example,
> root=PARTUUID=99DE9194-FC15-4223-9192-FC243948F88B/PARTNROFF=1
> selects the partition with UUID 99DE.. then select the next
> partition.
>
> This change is motivated by a particular usecase in Chromium OS where
> the bootloader can easily determine what partition it is on (by UUID)
> but doesn't perform general partition table walking.
>
> That said, support for this model provides a direct mechanism for the
> user to modify the root partition to boot without specifically needing
> to extract each UUID or update the bootloader explicitly when the root
> partition UUID is changed (if it is recreated to be larger, for
> instance). Pinning to a /boot-style partition UUID allows the arbitrary
> root partition reconfiguration/modifications with slightly less
> ambiguity than just [dev][partition] and less stringency than the
> specific root partition UUID.
>
> ...
>
> static dev_t devt_from_partuuid(char *uuid_str)
> @@ -98,6 +101,22 @@ static dev_t devt_from_partuuid(char *uuid_str)
> dev_t res = 0;
> struct device *dev = NULL;
> u8 uuid[16];
> + struct gendisk *disk;
> + struct hd_struct *part;
> + int offset = 0;
> +
> + if (strlen(uuid_str) < 36)
> + goto done;
I think this secretly changes behaviour? Previously the code would have
accepted a less-than-36-byte UUID and would have done <something> with
it. Now, it fails.
What was <something>, and what is the reason for this (undocumented!)
change?
> + /* Check for optional partition number offset attributes. */
> + if (uuid_str[36]) {
> + /* Explicitly fail on poor PARTUUID syntax. */
> + if (sscanf(&uuid_str[36], "/PARTNROFF=%d", &offset) != 1) {
> + printk(KERN_ERR "VFS: PARTUUID= is invalid.\n"
> + "Expected PARTUUID=<valid-uuid-id>[/PARTNROFF=%%d]\n");
The check isn't complete - afacit input of the form PARTNROFF=42foo
will be treated as PARTNROFF=42?
>
> ...
>
next prev parent reply other threads:[~2011-07-05 20:55 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-30 21:10 [PATCH v3 1/2] init: add root=PARTUUID=UUID/PARTNROFF=%d support Will Drewry
2011-06-30 21:10 ` [PATCH v3 2/2] Documentation: add pointer to name_to_dev_t for root= values Will Drewry
2011-07-05 20:53 ` Andrew Morton [this message]
2011-07-06 18:01 ` [PATCH v3 1/2] init: add root=PARTUUID=UUID/PARTNROFF=%d support Will Drewry
2011-07-25 19:55 ` [PATCH] init: clean up devt_from_partuuid syntax checking and logging Will Drewry
2011-07-25 20:47 ` [PATCH v3 1/2] init: add root=PARTUUID=UUID/PARTNROFF=%d support H. Peter Anvin
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