On 26/08/2014 22:53, Chris Mason wrote:
On 08/26/2014 10:51 AM, Eric Sandeen wrote:
On 8/26/14, 5:55 AM, David Sterba wrote:
On Thu, Aug 21, 2014 at 08:08:57PM +0200, Goffredo Baroncelli wrote:
Of course I (we) don't care cdrom and/or floppy, but this raises
the question: are there other block devices which aren't showed in
proc/partitions ?
cdrom appears as /dev/sr0, floppy is /dev/fd0 if the respective modules
are loaded, no breakage here.
I am thinking to some less common hardware like
NON USB sd disk (I saw this kind of hardware, but now I don't have
it in my hands....).
A block device whose driver calls register_blkdev should appear in
proc/partitions, if not then I think it's a bug or a very non-standard
interface.
I don't know about any other cases where full /dev scan would reveal
something that /proc/partitions not, so I guess it's safe to remove it.
Yesterday, Chris did mention <something something mumble> about /dev/mapper/*
[12:57] <cmason> I got inconsistent results from /proc/partitions
[12:57] <cmason> this was 3 years ago now
[12:58] <cmason> it didn't find everything for dm devices, yeah
[12:58] <cmason> especially dm multipath got really confused
and I'll be honest, I didn't test with devicemapper devices, much
less dm multipath, so I suppose that's warranted prior to removal.
I'll see what I can do.
If there's a problem, I bet there's a solution that doesn't involve
scanning everything under /dev ...
That's definitely the problem I hit, but it was years ago. I'm willing
to bet we're safe to keep /proc/partitions now.
I was tempted to remove BTRFS_SCAN_PROC completely when I introduced
BTRFS_SCAN_LBLKID, but then there was less clarity on this as it is
now.
The point I am trying to make is that we could remove BTRFS_SCAN_PROC
all together and keep only the BTRFS_SCAN_LBLKID.
(Which means we shall remove the -d option under btrfs filesystem
show and btrfs device scan).
We could remove scanning /proc/partition (the BTRFS_SCAN_PROC)
because the libblkid (under scan method BTRFS_SCAN_LBLKID) would scan
both udev and /proc/partition by default. (as in the libblkid
man page). Further libblkid is end user configurable. end user can
override the default configuration and can scan either of udev
/dev/disk/by-* symlinks or /proc/partitions only.
Further if still some device is not found then it would be a libblkid
bug/enhancement, so we need to fix it under libblkid.
The scan method BTRFS_SCAN_PROC is redundant.
Thanks, Anand
-chris
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