[PATCH 0/3] mtd: core: protect access to mtd devices while in suspend

[Sean Nyekjaer]

Follow-up on discussion in https://lkml.org/lkml/2021/10/4/41

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.

@Miquel: I havn't covered every ioctl, to me it looks like they havn't
direct device access.

One (small) issue still present. gpmi_nand.c uses the rwsem before it's
initialized. Seems cumbersome to have every mtd/nand driver to call
init_waitqueue_head() and init_rwsem(). Could we somehow move the call
to mtd_set_dev_defaults() before nand_create_bbt()?

---
nand: device found, Manufacturer ID: 0x98, Chip ID: 0xdc
nand: Toshiba NAND 512MiB 3,3V 8-bit
nand: 512 MiB, SLC, erase size: 256 KiB, page size: 4096, OOB size: 128
------------[ cut here ]------------
WARNING: CPU: 0 PID: 1 at kernel/locking/rwsem.c:1240 down_read+0x160/0x184
DEBUG_RWSEMS_WARN_ON(sem->magic != sem): count = 0x0, magic = 0x0, owner = 0x0, curr 0xc40b0000, list not empty 
Modules linked in:
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.15.0-rc3-00002-g7eab985fa8cd-dirty #163 
Hardware name: Freescale i.MX6 Ultralite (Device Tree)
[<c010fa90>] (unwind_backtrace) from [<c010b8fc>] (show_stack+0x10/0x14)
[<c010b8fc>] (show_stack) from [<c0b34998>] (dump_stack_lvl+0x58/0x70)
[<c0b34998>] (dump_stack_lvl) from [<c0123884>] (__warn+0xd4/0x154) 
[<c0123884>] (__warn) from [<c0b2e9ac>] (warn_slowpath_fmt+0x94/0xbc)
[<c0b2e9ac>] (warn_slowpath_fmt) from [<c0b428c8>] (down_read+0x160/0x184)
[<c0b428c8>] (down_read) from [<c06df42c>] (mtd_read_oob+0xc8/0x284)
[<c06df42c>] (mtd_read_oob) from [<c06f28cc>] (scan_block_fast+0x78/0xf4) 
[<c06f28cc>] (scan_block_fast) from [<c06f3c14>] (search_bbt+0x268/0x304) 
[<c06f3c14>] (search_bbt) from [<c06f3ef0>] (nand_create_bbt+0x240/0x6dc) 
[<c06f3ef0>] (nand_create_bbt) from [<c06fa758>] (gpmi_nand_probe+0x568/0x6d0)
[<c06fa758>] (gpmi_nand_probe) from [<c068731c>] (platform_probe+0x58/0xb8)
[<c068731c>] (platform_probe) from [<c0684a48>] (really_probe.part.0+0x9c/0x32c)
[<c0684a48>] (really_probe.part.0) from [<c0684d78>] (__driver_probe_device+0xa0/0x138) 
[<c0684d78>] (__driver_probe_device) from [<c0684e40>] (driver_probe_device+0x30/0x10c) 
[<c0684e40>] (driver_probe_device) from [<c0685510>] (__driver_attach+0xb4/0x174) 
[<c0685510>] (__driver_attach) from [<c0682b84>] (bus_for_each_dev+0x78/0xb8) 
[<c0682b84>] (bus_for_each_dev) from [<c0683ea4>] (bus_add_driver+0xf0/0x1d8) 
[<c0683ea4>] (bus_add_driver) from [<c0686270>] (driver_register+0x88/0x118)
[<c0686270>] (driver_register) from [<c0102108>] (do_one_initcall+0x74/0x378) 
[<c0102108>] (do_one_initcall) from [<c1001304>] (kernel_init_freeable+0x2a4/0x348) 
[<c1001304>] (kernel_init_freeable) from [<c0b3bc34>] (kernel_init+0x10/0x124)
[<c0b3bc34>] (kernel_init) from [<c010011c>] (ret_from_fork+0x14/0x38)
Exception stack(0xc40a7fb0 to 0xc40a7ff8) 
7fa0: ???????? ???????? ???????? ???????? 
7fc0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ???????? 
7fe0: ???????? ???????? ???????? ???????? ???????? ???????? 
irq event stamp: 110936 
hardirqs lastenabled at (110935): [<c0100b04>] __irq_svc+0x64/0x80
hardirqs last disabled at (110936): [<c0100af0>] __irq_svc+0x50/0x80
softirqs lastenabled at (110906): [<c093818c>] netlink_insert+0x60/0x8a4
softirqs last disabled at (110904): [<c08ac6d4>] release_sock+0x18/0x98 
---[ end trace c70a1a8da23b619d ]---
Bad block table found at page 131008, version 0x01
Bad block table found at page 130944, version 0x01
---

Sean Nyekjaer (3):
  mtd: core: protect access to MTD devices while in suspend
  mtd: rawnand: remove suspended check
  mtd: mtdconcat: add suspend lock handling

 drivers/mtd/mtdconcat.c          |  11 ++-
 drivers/mtd/mtdcore.c            | 133 +++++++++++++++++++++++++++----
 drivers/mtd/nand/raw/nand_base.c |  52 +++---------
 include/linux/mtd/mtd.h          | 109 +++++++++++++++++++++----
 include/linux/mtd/rawnand.h      |   5 +-
 5 files changed, 234 insertions(+), 76 deletions(-)

-- 
2.33.0