Re: [PATCH v4 0/4] mtd: core: protect access to mtd devices while in suspend

From: Boris Brezillon
Date: Mon Nov 01 2021 - 03:47:09 EST


On Tue, 26 Oct 2021 07:55:47 +0200
Sean Nyekjaer <sean@xxxxxxxxxx> wrote:

> Follow-up on discussion in:
> https://lkml.org/lkml/2021/10/4/41
> https://lkml.org/lkml/2021/10/11/435
>
> Changes since v3:
> - edited commit msg and author for mtdconcat patch
>
> Changes since v2:
> - added signoff's to patch from Boris
> - removed accidential line break
> - kept tests consistent: master->master.suspended == 0 -> !master->master.suspended
> - added comments to mtdconcat patch
> - moved mtdconcat before ('mtd: core: protect access to MTD devices while in suspend')
>
> Changes since v1:
> - removed __mtd_suspend/__mtd_resume functions as they are not used by
> mtdconcat anymore.
> - only master mtd_info is used for mtd_{start,end}_access(). Warn if we
> got mtd's.
> - added Boris patch for using uninitialized _suspend/_resume hooks when
> bbt scanning
> - mtdconcat uses device _suspend/_resume hooks
> - I don't really like the macro proposal from Boris
> mtd_no_suspend_void_call()/mtd_no_suspend_ret_call() I think they
> make the code complex to read and the macro's doesn't fit every
> where anyway...
>
> Changes since from rfc v1/v2:
> - added access protection for all device access hooks in mtd_info.
> - added Suggested-by to [1/3] patch.
> - removed refereces to commit ef347c0cfd61 ("mtd: rawnand: gpmi: Implement exec_op")
> from commit msg as commit 013e6292aaf5 ("mtd: rawnand: Simplify the locking") is
> to be blamed.
> - tested on a kernel with LOCKDEP enabled.
>
> Boris Brezillon (2):
> mtd: rawnand: nand_bbt: hide suspend/resume hooks while scanning bbt
> mtd: mtdconcat: don't use mtd_{suspend,resume}()
>
> Sean Nyekjaer (2):
> mtd: core: protect access to MTD devices while in suspend
> mtd: rawnand: remove suspended check

Looks good overall (after fixing the minor things I pointed out, of
course), but I'd recommend applying this series to mtd-next just after
-rc1 is out so you get a chance to detect regressions before it's
merged in Linus' tree. I fear this unconditional blocking on suspended
device will lead to unexpected deadlocks (see my comment on panic
writes)...

>
> drivers/mtd/mtdconcat.c | 15 +++-
> drivers/mtd/mtdcore.c | 124 +++++++++++++++++++++++++++----
> drivers/mtd/nand/raw/nand_base.c | 52 ++++---------
> drivers/mtd/nand/raw/nand_bbt.c | 28 ++++++-
> include/linux/mtd/mtd.h | 81 ++++++++++++++++----
> include/linux/mtd/rawnand.h | 5 +-
> 6 files changed, 230 insertions(+), 75 deletions(-)
>