From: Boaz Harrosh <openosd@gmail.com>
To: Matthew Wilcox <willy@linux.intel.com>
Cc: Matthew Wilcox <matthew.r.wilcox@intel.com>,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org,
"Martin K. Petersen" <martin.petersen@oracle.com>
Subject: Re: [PATCH v8 04/22] Change direct_access calling convention
Date: Thu, 31 Jul 2014 21:04:08 +0300 [thread overview]
Message-ID: <53DA8518.3090604@gmail.com> (raw)
In-Reply-To: <20140731171953.GU6754@linux.intel.com>
On 07/31/2014 08:19 PM, Matthew Wilcox wrote:
> On Thu, Jul 31, 2014 at 06:28:37PM +0300, Boaz Harrosh wrote:
>> Matthew what is your opinion about this, do we need to push for removal
>> of the partition dead code which never worked for brd, or we need to push
>> for fixing and implementing new partition support for brd?
>
> Fixing the code gets my vote. brd is useful for testing things ... and
> sometimes we need to test things that involve partitions.
>
OK I'm on it, its what I'm doing today.
rrr I manged to completely trash my vm by doing 'make install' of
util-linux and after reboot it never recovered, I remember that
mount complained about a now missing library and I forgot and rebooted,
that was the end of that. Anyway I installed a new fc20 system wanted
that for a long time over my old fc18
>> Also another thing I saw is that if we leave the flag
>> GENHD_FL_SUPPRESS_PARTITION_INFO
>>
>> then mount -U UUID stops to work, regardless of partitions or not,
>> this is because Kernel will not put us on /proc/patitions.
>> I'll submit another patch to remove it.
>
> Yes, we should probably fix that too.
>
Yes this is good stuff. I found out about the gpt option in fdisk
that's really good stuff because it gives you a PARTUUID even before
the mkfs, and the partitions are so mach more logical.
But only without that flag
>> BTW I hit another funny bug where the partition beginning was not
>> 4K aligned apparently fdisk lets you do this if the total size is small
>> enough (like 4096 which is default for brd) so I ended up with accessing
>> sec zero, the supper-block, failing because of the alignment check at
>> direct_access().
>
> That's why I added on the partition start before doing the alignment
> check :-)
>
Yes, exactly, I had very similar code to yours. I moved to your code
now First patch in the set is your patch 4/22 squashed with the modifications
you sent, then my fix, then the getgeo patch, then the remove of the flag.
But I'm still fighting fdisk's sector math, I can't for the life of me
figure out fdisk math, and it is all too easy to create a partition schema
that has an unaligned first/last sector.
I can observe and see the dis-alignment when the partitions are first
created, I can detect that at prd_probe time.
I can probably fix it by this logic:
When first detecting a new partition ie if bd_part->start_sect
is not aligned round-up to PAGE_SIZE. Then subtract from bd_part->nr_sects the
fixed up size and round-down bd_part->nr_sects to PAGE_SIZE
This way I still live inside the confined space that fdisk gave me but only IO
within largest aligned space. The leftover sectors are just wasted space.
>> Do you know of any API that brd/prd can do to not let fdisk do this?
>> I'm looking at it right now I just thought it is worth asking.
>
> I think it's enough to refuse the mount. That feels like a patch to
> ext2/4 (or maybe ext2/4 has a way to start the filesystem on a different
> block boundary?)
>
We should not leave this to the FSs to do again and again all over. I wonder
if there is some getgeo or some disk properties info somewhere that I can
set to force the core block layer to do this for me, I'm surprised that this
is the first place we have this problem?
Thanks
Boaz
next prev parent reply other threads:[~2014-07-31 18:04 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-22 19:47 [PATCH v8 00/22] Support ext4 on NV-DIMMs Matthew Wilcox
2014-07-22 19:47 ` [PATCH v8 01/22] Fix XIP fault vs truncate race Matthew Wilcox
2014-07-23 11:21 ` Kirill A. Shutemov
2014-07-22 19:47 ` [PATCH v8 02/22] Allow page fault handlers to perform the COW Matthew Wilcox
2014-07-23 11:23 ` Kirill A. Shutemov
2014-07-22 19:47 ` [PATCH v8 03/22] axonram: Fix bug in direct_access Matthew Wilcox
2014-07-23 11:24 ` Kirill A. Shutemov
2014-07-22 19:47 ` [PATCH v8 04/22] Change direct_access calling convention Matthew Wilcox
2014-07-30 16:03 ` Boaz Harrosh
2014-07-30 16:12 ` Boaz Harrosh
2014-07-30 20:34 ` Matthew Wilcox
2014-07-31 10:16 ` Boaz Harrosh
2014-07-30 19:45 ` Matthew Wilcox
2014-07-31 10:11 ` Boaz Harrosh
2014-07-31 14:13 ` Matthew Wilcox
2014-07-31 15:28 ` Boaz Harrosh
2014-07-31 17:19 ` Matthew Wilcox
2014-07-31 18:04 ` Boaz Harrosh [this message]
2014-07-31 20:30 ` Zwisler, Ross
2014-08-01 18:45 ` Zwisler, Ross
2014-07-22 19:47 ` [PATCH v8 05/22] Add vm_replace_mixed() Matthew Wilcox
2014-07-23 9:10 ` Jan Kara
2014-07-23 11:45 ` Kirill A. Shutemov
2014-07-23 13:52 ` Matthew Wilcox
2014-07-23 14:20 ` Kirill A. Shutemov
2014-07-23 14:27 ` Matthew Wilcox
2014-07-23 15:55 ` Kirill A. Shutemov
2014-07-24 1:36 ` Zhang, Tianfei
2014-07-25 19:44 ` Matthew Wilcox
2014-07-28 13:25 ` Kirill A. Shutemov
2014-07-29 1:55 ` Zhang, Tianfei
2014-07-22 19:47 ` [PATCH v8 06/22] Introduce IS_DAX(inode) Matthew Wilcox
2014-07-22 19:47 ` [PATCH v8 07/22] Add copy_to_iter(), copy_from_iter() and iov_iter_zero() Matthew Wilcox
2014-07-22 19:47 ` [PATCH v8 08/22] Replace XIP read and write with DAX I/O Matthew Wilcox
2014-07-22 19:47 ` [PATCH v8 09/22] Replace ext2_clear_xip_target with dax_clear_blocks Matthew Wilcox
2014-07-22 19:47 ` [PATCH v8 10/22] Replace the XIP page fault handler with the DAX page fault handler Matthew Wilcox
2014-07-23 12:10 ` Kirill A. Shutemov
2014-07-23 13:55 ` Matthew Wilcox
2014-07-23 14:10 ` [PATCH v8 00/22] Support ext4 on NV-DIMMs Howard Chu
2014-07-23 14:34 ` Matthew Wilcox
2014-07-23 15:28 ` Howard Chu
2014-07-23 20:55 ` Theodore Ts'o
2014-07-23 16:57 ` [PATCH v8 10/22] Replace the XIP page fault handler with the DAX page fault handler Boaz Harrosh
2014-07-23 19:57 ` Matthew Wilcox
2014-07-22 19:47 ` [PATCH v8 11/22] Replace xip_truncate_page with dax_truncate_page Matthew Wilcox
2014-07-22 19:48 ` [PATCH v8 12/22] Replace XIP documentation with DAX documentation Matthew Wilcox
2014-07-22 19:48 ` [PATCH v8 13/22] Remove get_xip_mem Matthew Wilcox
2014-07-22 19:48 ` [PATCH v8 14/22] ext2: Remove ext2_xip_verify_sb() Matthew Wilcox
2014-07-22 19:48 ` [PATCH v8 15/22] ext2: Remove ext2_use_xip Matthew Wilcox
2014-07-22 19:48 ` [PATCH v8 16/22] ext2: Remove xip.c and xip.h Matthew Wilcox
2014-07-22 19:48 ` [PATCH v8 17/22] Remove CONFIG_EXT2_FS_XIP and rename CONFIG_FS_XIP to CONFIG_FS_DAX Matthew Wilcox
2014-07-22 19:48 ` [PATCH v8 18/22] ext2: Remove ext2_aops_xip Matthew Wilcox
2014-07-22 19:48 ` [PATCH v8 19/22] Get rid of most mentions of XIP in ext2 Matthew Wilcox
2014-07-22 19:48 ` [PATCH v8 20/22] xip: Add xip_zero_page_range Matthew Wilcox
2014-07-22 19:48 ` [PATCH v8 21/22] ext4: Add DAX functionality Matthew Wilcox
2014-07-22 19:48 ` [PATCH v8 22/22] brd: Rename XIP to DAX Matthew Wilcox
2014-07-23 12:30 ` [PATCH v8 00/22] Support ext4 on NV-DIMMs Kirill A. Shutemov
2014-07-23 13:59 ` Matthew Wilcox
2014-07-23 15:58 ` Boaz Harrosh
2014-07-23 19:50 ` Matthew Wilcox
2014-07-24 18:51 ` Ross Zwisler
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