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SubjectRe: [RFC v5 0/4] pstore/block: new support logger for block devices
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On 2019-01-08 05:47, Kees Cook wrote:
> On Mon, Jan 7, 2019 at 4:01 AM liaoweixiong
> <liaoweixiong@allwinnertech.com> wrote:
>>
>> Why should we need pstore_block?
>> 1. Most embedded intelligent equipment have no persistent ram, which
>> increases costs. We perfer to cheaper solutions, like block devices.
>> In fast, there is already a sample for block device logger in driver
>> MTD (drivers/mtd/mtdoops.c).
>> 2. Do not any equipment have battery, which means that it lost all data
>> on general ram if power failure. Pstore has little to do for these
>> equipments.
>
> I'm catching up from being off over the holidays, but I just wanted to
> say that I like the general idea here.

Thanks for your work very much! :)

>
>> [PATCH v5]
>> On patch 1:
>> 1. rename pstore/rom to pstore/blk
>
> Thanks! The earlier name seemed wrong. :)
>
>> 2. Do not allocate any memory in the write path of panic. So, use local
>> array instead in function romz_recover_dmesg_meta.
>> 3. Add C header file "linux/fs.h" to fix implicit declaration of function
>> 'filp_open','kernel_read'...
>> On patch 3:
>> 1. If panic, do not recover pmsg but flush if it is dirty.
>> 2. Fix erase pmsg failed.
>> On patch 4:
>> 1. Create a document for pstore/blk
>
> Overall, I wonder if more of the ram backend code could get reused for
> the blk backend? I'd much rather be able to share that, since much of
> the logic is the same.

Before I wrote pstore/blk, I specially studied pstore/ram. As your
words, much of the logic is the same, you will see some codes similar to
pstore/ram.
But there is still something different with pstore/ram. For example,
block device maybe unready for read/write before kernel finish
initializing. So, pstore/blk recovers old data when mount rather than
initialize.
In addition, pstore/blk could not be used for pstore-console, since
block device much slower than ram.
In my original design, pstore/blk works like a manager for storage
space, don't care if it is ram or block device. So, it may works for
persistent ram too.

>
> I'll get to a more detailed review in the coming days. Thanks for sending this!
>
> -Kees
>
>>
>> [PATCH v4]
>> On patch 1:
>> 1. Fix always true condition '(--i >= 0) => (0-u32max >= 0)' in function
>> romz_init_zones by defining variable i to 'int' rahter than
>> 'unsigned int'.
>> 2. To make codes more easily to read, we use macro READ_NEXT_ZONE for
>> return value of romz_dmesg_read if it need to read next zone.
>> Moveover, we assign READ_NEXT_ZONE -1024 rather than 0.
>> 3. Add 'FLUSH_META' to 'enum romz_flush_mode' and rename 'NOT_FLUSH' to
>> 'FLUSH_NONE'
>> 4. Function romz_zone_write work badly with FLUSH_PART mode as badly
>> address and offset to write.
>> On patch 3:
>> NEW SUPPORT psmg for pstore_rom.
>>
>> [PATCH v3]
>> On patch 1:
>> Fix build as module error for undefined 'vfs_read' and 'vfs_write'
>> Both of 'vfs_read' and 'vfs_write' haven't be exproted yet, so we use
>> 'kernel_read' and 'kernel_write' instead.
>>
>> [PATCH v2]
>> On patch 1:
>> Fix build as module error for redefinition of 'romz_unregister' and
>> 'romz_register'
>>
>> [PATCH v1]
>> On patch 1:
>> Core codes of pstore_rom, which works well on allwinner(sunxi) platform.
>> On patch 2:
>> A sample for pstore_rom, using general ram rather than block device.
>>
>> liaoweixiong (4):
>> pstore/blk: new support logger for block devices
>> pstore/blk: add sample for pstore_blk
>> pstore/blk: support pmsg for pstore block
>> Documentation: pstore/blk: create document for pstore_blk
>>
>> Documentation/admin-guide/pstore-block.rst | 226 ++++++
>> MAINTAINERS | 1 +
>> fs/pstore/Kconfig | 20 +
>> fs/pstore/Makefile | 5 +
>> fs/pstore/blkbuf.c | 46 ++
>> fs/pstore/blkzone.c | 1168 ++++++++++++++++++++++++++++
>> include/linux/pstore_blk.h | 62 ++
>> 7 files changed, 1528 insertions(+)
>> create mode 100644 Documentation/admin-guide/pstore-block.rst
>> create mode 100644 fs/pstore/blkbuf.c
>> create mode 100644 fs/pstore/blkzone.c
>> create mode 100644 include/linux/pstore_blk.h
>>
>> --
>> 1.9.1
>>
>
>

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