Re: next-20250721 arm64 16K and 64K page size WARNING fs fuse file.c at fuse_iomap_writeback_range

["Darrick J. Wong" <djwong@kernel.org>]

[cc Joanne]

On Wed, Jul 23, 2025 at 05:14:28PM +0530, Naresh Kamboju wrote:
> Regressions found while running LTP msync04 tests on qemu-arm64 running
> Linux next-20250721, next-20250722 and next-20250723 with 16K and 64K
> page size enabled builds.
> 
> CONFIG_ARM64_64K_PAGES=y ( kernel warning as below )
> CONFIG_ARM64_16K_PAGES=y ( kernel warning as below )
> 
> No warning noticed with 4K page size.
> CONFIG_ARM64_4K_PAGES=y works as expected

You might want to cc Joanne since she's been working on large folio
support in fuse.

> First seen on the tag next-20250721.
> Good: next-20250718
> Bad:  next-20250721 to next-20250723
> 
> Regression Analysis:
> - New regression? Yes
> - Reproducibility? Yes
> 
> Test regression: next-20250721 arm64 16K and 64K page size WARNING fs
> fuse file.c at fuse_iomap_writeback_range
> 
> Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
> 
> ## Test log
> ------------[ cut here ]------------
> [  343.828105] WARNING: fs/fuse/file.c:2146 at
> fuse_iomap_writeback_range+0x478/0x558 [fuse], CPU#0: msync04/4190

	WARN_ON_ONCE(len & (PAGE_SIZE - 1));

/me speculates that this might be triggered by an attempt to write back
some 4k fsblock within a 16/64k base page?

--D

> [  343.830969] Modules linked in: btrfs blake2b_generic xor xor_neon
> raid6_pq zstd_compress sm3_ce sha3_ce drm fuse backlight ip_tables
> x_tables
> [  343.833830] CPU: 0 UID: 0 PID: 4190 Comm: msync04 Not tainted
> 6.16.0-rc7-next-20250723 #1 PREEMPT
> [  343.834736] Hardware name: linux,dummy-virt (DT)
> [  343.835788] pstate: 03402009 (nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
> [  343.836455] pc : fuse_iomap_writeback_range+0x478/0x558 fuse
> [  343.837294] lr : iomap_writeback_folio (fs/iomap/buffered-io.c:1586
> fs/iomap/buffered-io.c:1710)
> [  343.838178] sp : ffff80008b26f8d0
> [  343.838668] x29: ffff80008b26f8d0 x28: fff00000e7f8c800 x27: 0000000000000000
> [  343.839391] x26: fff00000d4b30000 x25: 0000000000000000 x24: 0000000000000000
> [  343.840305] x23: 0000000000000000 x22: fffffc1fc0334200 x21: 0000000000001000
> [  343.840928] x20: ffff80008b26fa00 x19: 0000000000000000 x18: 0000000000000000
> [  343.841782] x17: 0000000000000000 x16: ffffb8d3b90c67c8 x15: 0000000000000000
> [  343.842565] x14: ffffb8d3ba91e340 x13: 0000ffff8ff3ffff x12: 0000000000000000
> [  343.843002] x11: 1ffe000004b74a21 x10: fff0000025ba510c x9 : ffffb8d3b90c6308
> [  343.843962] x8 : ffff80008b26f788 x7 : ffffb8d365830b90 x6 : ffffb8d3bb6c9000
> [  343.844718] x5 : 0000000000000000 x4 : 000000000000000a x3 : 0000000000001000
> [  343.845333] x2 : fff00000c0b5ecc0 x1 : 000000000000ffff x0 : 0bfffe000000400b
> [  343.846323] Call trace:
> [  343.846767] fuse_iomap_writeback_range+0x478/0x558 fuse (P)
> [  343.847288] iomap_writeback_folio (fs/iomap/buffered-io.c:1586
> fs/iomap/buffered-io.c:1710)
> [  343.847930] iomap_writepages (fs/iomap/buffered-io.c:1762)
> [  343.848494] fuse_writepages+0xa0/0xe8 fuse
> [  343.849112] do_writepages (mm/page-writeback.c:2634)
> [  343.849614] filemap_fdatawrite_wbc (mm/filemap.c:386 mm/filemap.c:376)
> [  343.850202] __filemap_fdatawrite_range (mm/filemap.c:420)
> [  343.850791] file_write_and_wait_range (mm/filemap.c:794)
> [  343.851108] fuse_fsync+0x6c/0x138 fuse
> [  343.851688] vfs_fsync_range (fs/sync.c:188)
> [  343.852002] __arm64_sys_msync (mm/msync.c:96 mm/msync.c:32 mm/msync.c:32)
> [  343.852197] invoke_syscall.constprop.0
> (arch/arm64/include/asm/syscall.h:61 arch/arm64/kernel/syscall.c:54)
> [  343.852914] do_el0_svc (include/linux/thread_info.h:135
> (discriminator 2) arch/arm64/kernel/syscall.c:140 (discriminator 2)
> arch/arm64/kernel/syscall.c:151 (discriminator 2))
> [  343.853389] el0_svc (arch/arm64/include/asm/irqflags.h:82
> (discriminator 1) arch/arm64/include/asm/irqflags.h:123 (discriminator
> 1) arch/arm64/include/asm/irqflags.h:136 (discriminator 1)
> arch/arm64/kernel/entry-common.c:169 (discriminator 1)
> arch/arm64/kernel/entry-common.c:182 (discriminator 1)
> arch/arm64/kernel/entry-common.c:880 (discriminator 1))
> [  343.853829] el0t_64_sync_handler (arch/arm64/kernel/entry-common.c:899)
> [  343.854350] el0t_64_sync (arch/arm64/kernel/entry.S:596)
> [  343.854652] ---[ end trace 0000000000000000 ]---
> 
> 
> 
> ## Source
> * Git tree: https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next.git
> * Project: https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20250723/
> * Git sha: a933d3dc1968fcfb0ab72879ec304b1971ed1b9a
> * Git describe: 6.16.0-rc7-next-20250723
> * kernel version: next-20250723
> * Architectures: arm64
> * Toolchains: gcc-13
> * Kconfigs: defconfig + CONFIG_ARM64_64K_PAGES=y
> * Kconfigs: defconfig + CONFIG_ARM64_16K_PAGES=y
> 
> ## Test
> * Test log 1: https://qa-reports.linaro.org/api/testruns/29227309/log_file/
> * Test log 2: https://qa-reports.linaro.org/api/testruns/29227074/log_file/
> * Test run: https://regressions.linaro.org/lkft/linux-next-master/next-20250723/testruns/1713367/
> * Test history:
> https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20250723/testrun/29227309/suite/log-parser-test/test/exception-warning-fsfusefile-at-fuse_iomap_writeback_range/history/
> * Test plan: https://tuxapi.tuxsuite.com/v1/groups/linaro/projects/lkft/tests/30G3hpJVVdXkZKnB15v1qoQOL03
> * Build link: https://storage.tuxsuite.com/public/linaro/lkft/builds/30G3dvSFyHHQ3E8CvKH7tjU98I6/
> * Kernel config:
> https://storage.tuxsuite.com/public/linaro/lkft/builds/30G3dvSFyHHQ3E8CvKH7tjU98I6/config
> 
> --
> Linaro LKFT
> https://lkft.linaro.org