On Wed, Jul 23, 2025 at 7:46 AM Darrick J. Wong djwong@kernel.org wrote:
[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
Thanks for the report. Is there a link to the script that mounts the fuse server for these tests? I'm curious whether this was mounted as a fuseblk filesystem.
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?
I think this can happen on 4k base pages as well actually. On the iomap side, the length passed is always block-aligned and in fuse, we set blkbits to be PAGE_SHIFT so theoretically block-aligned is always page-aligned, but I missed that if it's a "fuseblk" filesystem, that isn't true and the blocksize is initialized to a default size of 512 or whatever block size is passed in when it's mounted.
I'll send out a patch to remove this line. It doesn't make any difference for fuse_iomap_writeback_range() logic whether len is page-aligned or not; I had added it as a sanity-check against sketchy ranges.
Also, I just noticed that apparently the blocksize can change dynamically for an inode in fuse through getattr replies from the server (see fuse_change_attributes_common()). This is a problem since the iomap uses inode->i_blkbits for reading/writing to the bitmap. I think we will have to cache the inode blkbits in the iomap_folio_state struct unfortunately :( I'll think about this some more and send out a patch for this.
Thanks, Joanne
--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
- 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...
- Test history:
https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20250723/tes...
- Test plan: https://tuxapi.tuxsuite.com/v1/groups/linaro/projects/lkft/tests/30G3hpJVVdX...
- Build link: https://storage.tuxsuite.com/public/linaro/lkft/builds/30G3dvSFyHHQ3E8CvKH7t...
- Kernel config:
https://storage.tuxsuite.com/public/linaro/lkft/builds/30G3dvSFyHHQ3E8CvKH7t...
-- Linaro LKFT https://lkft.linaro.org