Merge tag 'ffa-fixes-6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux into arm/fixes

Arm FF-A fixes for v6.8

Quite a few fixes addressing issues around missing RW lock initialisation
in ffa_setup_partitions(), missing check for xa_load() return value,
use of xa_insert instead of xa_store to flag case of duplicate insertion.
It also simplifies ffa_partitions_cleanup() with xa_for_each() and xa_erase()
instead of xa_extract() and kfree(). Finally it includes fixes around
handling of partitions setup failures during initialisation.

* tag 'ffa-fixes-6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux:
  firmware: arm_ffa: Handle partitions setup failures
  firmware: arm_ffa: Use xa_insert() and check for result
  firmware: arm_ffa: Simplify ffa_partitions_cleanup()
  firmware: arm_ffa: Check xa_load() return value
  firmware: arm_ffa: Add missing rwlock_init() for the driver partition
  firmware: arm_ffa: Add missing rwlock_init() in ffa_setup_partitions()

Link: https://lore.kernel.org/r/20240122161652.3551159-1-sudeep.holla@arm.comSigned-off-by: Arnd Bergmann <arnd@arndb.de>

Merge tag 'scmi-fixes-6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux into arm/fixes

Arm SCMI fixes for v6.8

Few fixes addressing the below issues:

1. A spurious IRQ related to the late reply can get wrongly associated
   with the new enqueued request resulting in misinterpretation of data
   in shared memory. This race-condition can be detected by looking at
   the channel status bits which the platform must set to the channel
   free before triggering the completion IRQ. Adding a consistency check
   to validate such condition will fix the issue.
2. Incorrect use of asm-generic/bug.h instead of generic linux/bUg.h
3. xa_store() can't check for possible duplication insertion, use
   xa_insert() instead
4. Fix the SCMI clock protocol version in the v3.2 SCMI specification
5. Incorrect upgrade of highest supported clock protocol version from
   v2.0 to v3.0

* tag 'scmi-fixes-6.8' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux:
  firmware: arm_scmi: Fix the clock protocol supported version
  firmware: arm_scmi: Fix the clock protocol version for v3.2
  firmware: arm_scmi: Use xa_insert() when saving raw queues
  firmware: arm_scmi: Use xa_insert() to store opps
  firmware: arm_scmi: Replace asm-generic/bug.h with linux/bug.h
  firmware: arm_scmi: Check mailbox/SMT channel for consistency

Link: https://lore.kernel.org/r/20240122161640.3551085-1-sudeep.holla@arm.comSigned-off-by: Arnd Bergmann <arnd@arndb.de>

Since commit 26c9d152 ("dt-bindings: tpm: Consolidate TCG TIS
bindings"), several issues are reported by "make dtbs_check" for arm64
devicetrees:

The compatible property needs to contain the chip's name in addition to
the generic "tcg,tpm_tis-spi" and the nodename needs to be "tpm@0"
rather than "cr50@0":

  tpm@1: compatible: ['tcg,tpm_tis-spi'] is too short
        from schema $id: http://devicetree.org/schemas/tpm/tcg,tpm_tis-spi.yaml#

  cr50@0: $nodename:0: 'cr50@0' does not match '^tpm(@[0-9a-f]+)?$'
        from schema $id: http://devicetree.org/schemas/tpm/google,cr50.yaml#

Fix these schema violations.

phyGATE-Tauri uses an Infineon SLB9670:
https://lore.kernel.org/all/ab45c82485fa272f74adf560cbb58ee60cc42689.camel@phytec.de/

Gateworks Venice uses an Atmel ATTPM20P:
https://trac.gateworks.com/wiki/tpmSigned-off-by: Lukas Wunner <lukas@wunner.de>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

Since commit 26c9d152 ("dt-bindings: tpm: Consolidate TCG TIS
bindings"), several issues are reported by "make dtbs_check" for ARM
devicetrees:

The nodename needs to be "tpm@0" rather than "tpmdev@0" and the
compatible property needs to contain the chip's name in addition to the
generic "tcg,tpm_tis-spi" or "tcg,tpm-tis-i2c":

  tpmdev@0: $nodename:0: 'tpmdev@0' does not match '^tpm(@[0-9a-f]+)?$'
        from schema $id: http://devicetree.org/schemas/tpm/tcg,tpm_tis-spi.yaml#

  tpm@2e: compatible: 'oneOf' conditional failed, one must be fixed:
        ['tcg,tpm-tis-i2c'] is too short
        from schema $id: http://devicetree.org/schemas/tpm/tcg,tpm-tis-i2c.yaml#

Fix these schema violations.

Aspeed Facebook BMCs use an Infineon SLB9670:
https://lore.kernel.org/all/ZZSmMJ%2F%2Fl972Qbxu@fedora/
https://lore.kernel.org/all/ZZT4%2Fw2eVzMhtsPx@fedora/
https://lore.kernel.org/all/ZZTS0p1hdAchIbKp@heinlein.vulture-banana.ts.net/

Aspeed Tacoma uses a Nuvoton NPCT75X per commit 39d8a73c ("ARM: dts:
aspeed: tacoma: Add TPM").

phyGATE-Tauri uses an Infineon SLB9670:
https://lore.kernel.org/all/ab45c82485fa272f74adf560cbb58ee60cc42689.camel@phytec.de/

A single schema violation remains in am335x-moxa-uc-2100-common.dtsi
because it is unknown which chip is used on the board.  The devicetree's
author has been asked for clarification but has not responded so far:
https://lore.kernel.org/all/20231220090910.GA32182@wunner.de/Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Patrick Williams <patrick@stwcx.xyz>
Reviewed-by: Tao Ren <rentao.bupt@gmail.com>
Reviewed-by: Bruno Thomsen <bruno.thomsen@gmail.com>

Make ffa_setup_partitions() fail, cleanup and return an error when the Host
partition setup fails: in such a case ffa_init() itself will fail.
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20240108-ffa_fixes_6-8-v1-6-75bf7035bc50@arm.comSigned-off-by: Sudeep Holla <sudeep.holla@arm.com>

While adding new partitions descriptors to the XArray the outcome of the
stores should be checked and, in particular, it has also to be ensured
that an existing entry with the same index was not already present, since
partitions IDs are expected to be unique.

Use xa_insert() instead of xa_store() since it returns -EBUSY when the
index is already in use and log an error when that happens.
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20240108-ffa_fixes_6-8-v1-5-75bf7035bc50@arm.comSigned-off-by: Sudeep Holla <sudeep.holla@arm.com>

On cleanup iterate the XArrays with xa_for_each() and remove the existent
entries with xa_erase(), finally destroy the XArray itself.

Remove partition_count field from drv_info since no more used anywhwere.
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20240108-ffa_fixes_6-8-v1-4-75bf7035bc50@arm.comSigned-off-by: Sudeep Holla <sudeep.holla@arm.com>

Add a check to verify the result of xa_load() during the partition
lookups done while registering/unregistering the scheduler receiver
interrupt callbacks and while executing the main scheduler receiver
interrupt callback handler.

Fixes: 0184450b ("firmware: arm_ffa: Add schedule receiver callback mechanism")
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20240108-ffa_fixes_6-8-v1-3-75bf7035bc50@arm.comSigned-off-by: Sudeep Holla <sudeep.holla@arm.com>

Add the missing rwlock initialization for the FF-A partition associated
the driver in ffa_setup_partitions(). It will the primary scheduler
partition in the host or the VM partition in the virtualised environment.
IOW, it corresponds to the partition with VM ID == drv_info->vm_id.

Fixes: 1b6bf41b ("firmware: arm_ffa: Add notification handling mechanism")
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20240108-ffa_fixes_6-8-v1-2-75bf7035bc50@arm.comSigned-off-by: Sudeep Holla <sudeep.holla@arm.com>

Add the missing rwlock initialization for the individual FF-A partition
information in ffa_setup_partitions().

Fixes: 0184450b ("firmware: arm_ffa: Add schedule receiver callback mechanism")
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20240108-ffa_fixes_6-8-v1-1-75bf7035bc50@arm.comSigned-off-by: Sudeep Holla <sudeep.holla@arm.com>

Rollback currently supported SCMI clock protocol version to v2.0 since
some of the mandatory v3.0 features are indeed still not supported yet.

Fixes: b5efc28a ("firmware: arm_scmi: Add protocol versioning checks")
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20240109181716.2338636-1-cristian.marussi@arm.comSigned-off-by: Sudeep Holla <sudeep.holla@arm.com>

The clock protocol version as per the SCMI v3.2 specification is 0x30000.
Enable the v3.0 clock protocol features only when clock protocol version
equals 0x30000.

The previous beta version of the spec had this value set to 0x20001 and
th same value trickled down from the initial development. The version
update were missed in the driver.

Fixes: e49e314a ("firmware: arm_scmi: Add clock v3.2 CONFIG_SET support")
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20240109150106.2066739-1-cristian.marussi@arm.comSigned-off-by: Sudeep Holla <sudeep.holla@arm.com>

Use xa_insert() when saving per-channel raw queues to better check for
duplicates.

Fixes: 7860701d ("firmware: arm_scmi: Add per-channel raw injection support")
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20240108185050.1628687-2-cristian.marussi@arm.comSigned-off-by: Sudeep Holla <sudeep.holla@arm.com>

When storing opps by level or index use xa_insert() instead of xa_store()
and add error-checking to spot bad duplicates indexes possibly wrongly
provided by the platform firmware.

Fixes: 31c7c139 ("firmware: arm_scmi: Add v3.2 perf level indexing mode support")
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20240108185050.1628687-1-cristian.marussi@arm.comSigned-off-by: Sudeep Holla <sudeep.holla@arm.com>

linux/bug.h includes asm-generic/bug.h already and hence replacing
asm-generic/bug.h with linux/bug.h will not regress any build.
Also, it is always better to avoid header file inclusion from asm-generic
if possible.
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Tanzir Hasan <tanzirh@google.com>
Link: https://lore.kernel.org/r/20231226-shmem-v1-1-ea15ce81d8ba@google.comSigned-off-by: Sudeep Holla <sudeep.holla@arm.com>

On reception of a completion interrupt the shared memory area is accessed
to retrieve the message header at first and then, if the message sequence
number identifies a transaction which is still pending, the related
payload is fetched too.

When an SCMI command times out the channel ownership remains with the
platform until eventually a late reply is received and, as a consequence,
any further transmission attempt remains pending, waiting for the channel
to be relinquished by the platform.

Once that late reply is received the channel ownership is given back
to the agent and any pending request is then allowed to proceed and
overwrite the SMT area of the just delivered late reply; then the wait
for the reply to the new request starts.

It has been observed that the spurious IRQ related to the late reply can
be wrongly associated with the freshly enqueued request: when that happens
the SCMI stack in-flight lookup procedure is fooled by the fact that the
message header now present in the SMT area is related to the new pending
transaction, even though the real reply has still to arrive.

This race-condition on the A2P channel can be detected by looking at the
channel status bits: a genuine reply from the platform will have set the
channel free bit before triggering the completion IRQ.

Add a consistency check to validate such condition in the A2P ISR.
Reported-by: Xinglong Yang <xinglong.yang@cixtech.com>
Closes: https://lore.kernel.org/all/PUZPR06MB54981E6FA00D82BFDBB864FBF08DA@PUZPR06MB5498.apcprd06.prod.outlook.com/
Fixes: 5c8a47a5 ("firmware: arm_scmi: Make scmi core independent of the transport type")
Cc: stable@vger.kernel.org # 5.15+
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Tested-by: Xinglong Yang <xinglong.yang@cixtech.com>
Link: https://lore.kernel.org/r/20231220172112.763539-1-cristian.marussi@arm.comSigned-off-by: Sudeep Holla <sudeep.holla@arm.com>

Pull more bcachefs updates from Kent Overstreet:
 "Some fixes, Some refactoring, some minor features:

   - Assorted prep work for disk space accounting rewrite

   - BTREE_TRIGGER_ATOMIC: after combining our trigger callbacks, this
     makes our trigger context more explicit

   - A few fixes to avoid excessive transaction restarts on
     multithreaded workloads: fstests (in addition to ktest tests) are
     now checking slowpath counters, and that's shaking out a few bugs

   - Assorted tracepoint improvements

   - Starting to break up bcachefs_format.h and move on disk types so
     they're with the code they belong to; this will make room to start
     documenting the on disk format better.

   - A few minor fixes"

* tag 'bcachefs-2024-01-21' of https://evilpiepirate.org/git/bcachefs: (46 commits)
  bcachefs: Improve inode_to_text()
  bcachefs: logged_ops_format.h
  bcachefs: reflink_format.h
  bcachefs; extents_format.h
  bcachefs: ec_format.h
  bcachefs: subvolume_format.h
  bcachefs: snapshot_format.h
  bcachefs: alloc_background_format.h
  bcachefs: xattr_format.h
  bcachefs: dirent_format.h
  bcachefs: inode_format.h
  bcachefs; quota_format.h
  bcachefs: sb-counters_format.h
  bcachefs: counters.c -> sb-counters.c
  bcachefs: comment bch_subvolume
  bcachefs: bch_snapshot::btime
  bcachefs: add missing __GFP_NOWARN
  bcachefs: opts->compression can now also be applied in the background
  bcachefs: Prep work for variable size btree node buffers
  bcachefs: grab s_umount only if snapshotting
  ...

Pull timer updates from Thomas Gleixner:
 "Updates for time and clocksources:

   - A fix for the idle and iowait time accounting vs CPU hotplug.

     The time is reset on CPU hotplug which makes the accumulated
     systemwide time jump backwards.

   - Assorted fixes and improvements for clocksource/event drivers"

* tag 'timers-core-2024-01-21' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  tick-sched: Fix idle and iowait sleeptime accounting vs CPU hotplug
  clocksource/drivers/ep93xx: Fix error handling during probe
  clocksource/drivers/cadence-ttc: Fix some kernel-doc warnings
  clocksource/drivers/timer-ti-dm: Fix make W=n kerneldoc warnings
  clocksource/timer-riscv: Add riscv_clock_shutdown callback
  dt-bindings: timer: Add StarFive JH8100 clint
  dt-bindings: timer: thead,c900-aclint-mtimer: separate mtime and mtimecmp regs

Pull powerpc fixes from Aneesh Kumar:

 - Increase default stack size to 32KB for Book3S

Thanks to Michael Ellerman.

* tag 'powerpc-6.8-2' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc/64s: Increase default stack size to 32KB

Add line breaks - inode_to_text() is now much easier to read.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

bcachefs_format.h has gotten too big; let's do some organizing.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Add a field to bch_snapshot for creation time; this will be important
when we start exposing the snapshot tree to userspace.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

The "apply this compression method in the background" paths now use the
compression option if background_compression is not set; this means that
setting or changing the compression option will cause existing data to
be compressed accordingly in the background.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

bcachefs btree nodes are big - typically 256k - and btree roots are
pinned in memory. As we're now up to 18 btrees, we now have significant
memory overhead in mostly empty btree roots.

And in the future we're going to start enforcing that certain btree node
boundaries exist, to solve lock contention issues - analagous to XFS's
AGIs.

Thus, we need to start allocating smaller btree node buffers when we
can. This patch changes code that refers to the filesystem constant
c->opts.btree_node_size to refer to the btree node buffer size -
btree_buf_bytes() - where appropriate.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

When I was testing mongodb over bcachefs with compression,
there is a lockdep warning when snapshotting mongodb data volume.

$ cat test.sh
prog=bcachefs

$prog subvolume create /mnt/data
$prog subvolume create /mnt/data/snapshots

while true;do
    $prog subvolume snapshot /mnt/data /mnt/data/snapshots/$(date +%s)
    sleep 1s
done

$ cat /etc/mongodb.conf
systemLog:
  destination: file
  logAppend: true
  path: /mnt/data/mongod.log

storage:
  dbPath: /mnt/data/

lockdep reports:
[ 3437.452330] ======================================================
[ 3437.452750] WARNING: possible circular locking dependency detected
[ 3437.453168] 6.7.0-rc7-custom+ #85 Tainted: G            E
[ 3437.453562] ------------------------------------------------------
[ 3437.453981] bcachefs/35533 is trying to acquire lock:
[ 3437.454325] ffffa0a02b2b1418 (sb_writers#10){.+.+}-{0:0}, at: filename_create+0x62/0x190
[ 3437.454875]
               but task is already holding lock:
[ 3437.455268] ffffa0a02b2b10e0 (&type->s_umount_key#48){.+.+}-{3:3}, at: bch2_fs_file_ioctl+0x232/0xc90 [bcachefs]
[ 3437.456009]
               which lock already depends on the new lock.

[ 3437.456553]
               the existing dependency chain (in reverse order) is:
[ 3437.457054]
               -> #3 (&type->s_umount_key#48){.+.+}-{3:3}:
[ 3437.457507]        down_read+0x3e/0x170
[ 3437.457772]        bch2_fs_file_ioctl+0x232/0xc90 [bcachefs]
[ 3437.458206]        __x64_sys_ioctl+0x93/0xd0
[ 3437.458498]        do_syscall_64+0x42/0xf0
[ 3437.458779]        entry_SYSCALL_64_after_hwframe+0x6e/0x76
[ 3437.459155]
               -> #2 (&c->snapshot_create_lock){++++}-{3:3}:
[ 3437.459615]        down_read+0x3e/0x170
[ 3437.459878]        bch2_truncate+0x82/0x110 [bcachefs]
[ 3437.460276]        bchfs_truncate+0x254/0x3c0 [bcachefs]
[ 3437.460686]        notify_change+0x1f1/0x4a0
[ 3437.461283]        do_truncate+0x7f/0xd0
[ 3437.461555]        path_openat+0xa57/0xce0
[ 3437.461836]        do_filp_open+0xb4/0x160
[ 3437.462116]        do_sys_openat2+0x91/0xc0
[ 3437.462402]        __x64_sys_openat+0x53/0xa0
[ 3437.462701]        do_syscall_64+0x42/0xf0
[ 3437.462982]        entry_SYSCALL_64_after_hwframe+0x6e/0x76
[ 3437.463359]
               -> #1 (&sb->s_type->i_mutex_key#15){+.+.}-{3:3}:
[ 3437.463843]        down_write+0x3b/0xc0
[ 3437.464223]        bch2_write_iter+0x5b/0xcc0 [bcachefs]
[ 3437.464493]        vfs_write+0x21b/0x4c0
[ 3437.464653]        ksys_write+0x69/0xf0
[ 3437.464839]        do_syscall_64+0x42/0xf0
[ 3437.465009]        entry_SYSCALL_64_after_hwframe+0x6e/0x76
[ 3437.465231]
               -> #0 (sb_writers#10){.+.+}-{0:0}:
[ 3437.465471]        __lock_acquire+0x1455/0x21b0
[ 3437.465656]        lock_acquire+0xc6/0x2b0
[ 3437.465822]        mnt_want_write+0x46/0x1a0
[ 3437.465996]        filename_create+0x62/0x190
[ 3437.466175]        user_path_create+0x2d/0x50
[ 3437.466352]        bch2_fs_file_ioctl+0x2ec/0xc90 [bcachefs]
[ 3437.466617]        __x64_sys_ioctl+0x93/0xd0
[ 3437.466791]        do_syscall_64+0x42/0xf0
[ 3437.466957]        entry_SYSCALL_64_after_hwframe+0x6e/0x76
[ 3437.467180]
               other info that might help us debug this:

[ 3437.469670] 2 locks held by bcachefs/35533:
               other info that might help us debug this:

[ 3437.467507] Chain exists of:
                 sb_writers#10 --> &c->snapshot_create_lock --> &type->s_umount_key#48

[ 3437.467979]  Possible unsafe locking scenario:

[ 3437.468223]        CPU0                    CPU1
[ 3437.468405]        ----                    ----
[ 3437.468585]   rlock(&type->s_umount_key#48);
[ 3437.468758]                                lock(&c->snapshot_create_lock);
[ 3437.469030]                                lock(&type->s_umount_key#48);
[ 3437.469291]   rlock(sb_writers#10);
[ 3437.469434]
                *** DEADLOCK ***

[ 3437.469670] 2 locks held by bcachefs/35533:
[ 3437.469838]  #0: ffffa0a02ce00a88 (&c->snapshot_create_lock){++++}-{3:3}, at: bch2_fs_file_ioctl+0x1e3/0xc90 [bcachefs]
[ 3437.470294]  #1: ffffa0a02b2b10e0 (&type->s_umount_key#48){.+.+}-{3:3}, at: bch2_fs_file_ioctl+0x232/0xc90 [bcachefs]
[ 3437.470744]
               stack backtrace:
[ 3437.470922] CPU: 7 PID: 35533 Comm: bcachefs Kdump: loaded Tainted: G            E      6.7.0-rc7-custom+ #85
[ 3437.471313] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.16.3-1-1 04/01/2014
[ 3437.471694] Call Trace:
[ 3437.471795]  <TASK>
[ 3437.471884]  dump_stack_lvl+0x57/0x90
[ 3437.472035]  check_noncircular+0x132/0x150
[ 3437.472202]  __lock_acquire+0x1455/0x21b0
[ 3437.472369]  lock_acquire+0xc6/0x2b0
[ 3437.472518]  ? filename_create+0x62/0x190
[ 3437.472683]  ? lock_is_held_type+0x97/0x110
[ 3437.472856]  mnt_want_write+0x46/0x1a0
[ 3437.473025]  ? filename_create+0x62/0x190
[ 3437.473204]  filename_create+0x62/0x190
[ 3437.473380]  user_path_create+0x2d/0x50
[ 3437.473555]  bch2_fs_file_ioctl+0x2ec/0xc90 [bcachefs]
[ 3437.473819]  ? lock_acquire+0xc6/0x2b0
[ 3437.474002]  ? __fget_files+0x2a/0x190
[ 3437.474195]  ? __fget_files+0xbc/0x190
[ 3437.474380]  ? lock_release+0xc5/0x270
[ 3437.474567]  ? __x64_sys_ioctl+0x93/0xd0
[ 3437.474764]  ? __pfx_bch2_fs_file_ioctl+0x10/0x10 [bcachefs]
[ 3437.475090]  __x64_sys_ioctl+0x93/0xd0
[ 3437.475277]  do_syscall_64+0x42/0xf0
[ 3437.475454]  entry_SYSCALL_64_after_hwframe+0x6e/0x76
[ 3437.475691] RIP: 0033:0x7f2743c313af
======================================================

In __bch2_ioctl_subvolume_create(), we grab s_umount unconditionally
and unlock it at the end of the function. There is a comment
"why do we need this lock?" about the lock coming from
commit 42d23732 ("bcachefs: Snapshot creation, deletion")
The reason is that __bch2_ioctl_subvolume_create() calls
sync_inodes_sb() which enforce locked s_umount to writeback all dirty
nodes before doing snapshot works.

Fix it by read locking s_umount for snapshotting only and unlocking
s_umount after sync_inodes_sb().
Signed-off-by: Su Yue <glass.su@suse.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>