Micron qspi nor flash and UBIFS

[Richard Weinberger]

Ping?

On Thu, Sep 1, 2016 at 12:23 PM, Richard Weinberger <richard at nod.at> wrote:
> Andras,
>
> On 01.09.2016 11:37, Andras Szemzo wrote:
>> UBIFS (ubi0:0): background thread "ubifs_bgt0_0" started, PID 47
>> ------------[ cut here ]------------
>> WARNING: CPU: 0 PID: 1 at drivers/mtd/spi-nor/spi-nor.c:1177 spi_nor_write+0x57/0xea
>> Writing at offset 128 into a NOR page. Writing partial pages may decrease reliability and increase wear of NOR flash.
>> Modules linked in:
>> CPU: 0 PID: 1 Comm: swapper Not tainted 4.8.0-rc2 #49
>> Hardware name: Atmel SAMx7
>> [<7000c5d9>] (unwind_backtrace) from [<7000b3ab>] (show_stack+0xb/0xc)
>> [<7000b3ab>] (show_stack) from [<7000f095>] (__warn+0x89/0xb0)
>> [<7000f095>] (__warn) from [<7000f0db>] (warn_slowpath_fmt+0x1f/0x28)
>> [<7000f0db>] (warn_slowpath_fmt) from [<70127e8d>] (spi_nor_write+0x57/0xea)
>> [<70127e8d>] (spi_nor_write) from [<70124593>] (part_write+0x27/0x2a)
>> [<70124593>] (part_write) from [<70122717>] (mtd_write+0x53/0x68)
>> [<70122717>] (mtd_write) from [<701301f3>] (ubi_io_write+0x23f/0x410)
>> [<701301f3>] (ubi_io_write) from [<7012e0f7>] (ubi_eba_write_leb+0x77/0x5fc)
>> [<7012e0f7>] (ubi_eba_write_leb) from [<7012d4c1>] (ubi_leb_write+0x71/0x8a)
>> [<7012d4c1>] (ubi_leb_write) from [<7009dd9d>] (ubifs_leb_write+0x65/0xb4)
>> [<7009dd9d>] (ubifs_leb_write) from [<7009edf3>] (ubifs_write_node+0xf7/0x124)
>> [<7009edf3>] (ubifs_write_node) from [<700a2945>] (ubifs_write_master+0x91/0xc8)
>> [<700a2945>] (ubifs_write_master) from [<7009c64f>] (ubifs_mount+0xebf/0x1020)
>> [<7009c64f>] (ubifs_mount) from [<700555e9>] (mount_fs+0x9/0x60)
>> [<700555e9>] (mount_fs) from [<7006427b>] (vfs_kern_mount+0x33/0xc0)
>> [<7006427b>] (vfs_kern_mount) from [<700664c9>] (do_mount+0x599/0x788)
>> [<700664c9>] (do_mount) from [<7006682b>] (SyS_mount+0x4f/0x6a)
>> [<7006682b>] (SyS_mount) from [<702cd8d1>] (mount_block_root+0xa9/0x1e8)
>> [<702cd8d1>] (mount_block_root) from [<702cdab1>] (prepare_namespace+0x4d/0xf0)
>> [<702cdab1>] (prepare_namespace) from [<702cd731>] (kernel_init_freeable+0x105/0x14c)
>> [<702cd731>] (kernel_init_freeable) from [<701c67db>] (kernel_init+0x7/0xa0)
>> [<701c67db>] (kernel_init) from [<70009c49>] (ret_from_fork+0x11/0x28)
>
> This proves my assumption.
> spi-nor.c warns as soon you write with an offset to a page.
> So, it will warn for *every* non-trivial user.
>
> The warning is also rather new, CC'ing patch authors.
>
> commit e5d05cbd6d8b01f08c95c427a36c66aac769af4f
> Author: Michal Suchanek <hramrach at gmail.com>
> Date:   Thu May 5 17:31:54 2016 -0700
>
>     mtd: spi-nor: simplify write loop
>
>     The spi-nor write loop assumes that what is passed to the hardware
>     driver write() is what gets written.
>
>     When write() writes less than page size at once data is dropped on the
>     floor. Check the amount of data writen and exit if it does not match
>     requested amount.
>
>     Signed-off-by: Michal Suchanek <hramrach at gmail.com>
>     Signed-off-by: Brian Norris <computersforpeace at gmail.com>
>     Tested-by Cyrille Pitchen <cyrille.pitchen at atmel.com>
>     Acked-by: Michal Suchanek <hramrach at gmail.com>
>     Tested-by: Michal Suchanek <hramrach at gmail.com>
>
>
> Guys, this patch is odd in multiple ways.
> 1. Patch description does not match the code. It does *not* just simplify the write loop.
>    It also introduces a new scary WARN_ON_ONCE(). Unless I miss something it will trigger
>    for every write with an offset. So, you rule out any filesystem on top of SPI-NOR.
>    What's the deal?
> 2. The SOB chain is strange. Michal, you authored this patch, right?
>    Why did you add an Acked-by and Tested-by tag too?
>
> Thanks,
> //richard
>
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-- 
Thanks,
//richard