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charset="UTF-8" > On Sun, Jan 04, 2026 at 06:40:21PM -0800, syzbot wrote: >> Hello, >> >> syzbot found the following issue on: >> >> HEAD commit: 8f0b4cce4481 Linux 6.19-rc1 >> git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci >> console output: https://syzkaller.appspot.com/x/log.txt?x=1481d792580000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=8a8594efdc14f07a >> dashboard link: https://syzkaller.appspot.com/bug?extid=c628140f24c07eb768d8 >> compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8 >> userspace arch: arm64 >> >> Unfortunately, I don't have any reproducer for this issue yet. >> >> Downloadable assets: >> disk image: https://storage.googleapis.com/syzbot-assets/cd4f5f43efc8/disk-8f0b4cce.raw.xz >> vmlinux: https://storage.googleapis.com/syzbot-assets/aafb35ac3a3c/vmlinux-8f0b4cce.xz >> kernel image: https://storage.googleapis.com/syzbot-assets/d221fae4ab17/Image-8f0b4cce.gz.xz >> >> IMPORTANT: if you fix the issue, please add the following tag to the commit: >> Reported-by: syzbot+c628140f24c07eb768d8@syzkaller.appspotmail.com >> >> WARNING: possible circular locking dependency detected >> syzkaller #0 Not tainted >> ------------------------------------------------------ >> syz.3.4/6790 is trying to acquire lock: >> ffff80008fb56c80 (fs_reclaim){+.+.}-{0:0}, at: might_alloc include/linux/sched/mm.h:317 [inline] >> ffff80008fb56c80 (fs_reclaim){+.+.}-{0:0}, at: slab_pre_alloc_hook mm/slub.c:4904 [inline] >> ffff80008fb56c80 (fs_reclaim){+.+.}-{0:0}, at: slab_alloc_node mm/slub.c:5239 [inline] >> ffff80008fb56c80 (fs_reclaim){+.+.}-{0:0}, at: __kmalloc_cache_noprof+0x58/0x698 mm/slub.c:5771 >> >> but task is already holding lock: >> ffff0000f77f5b18 (&xfs_nondir_ilock_class){++++}-{4:4}, at: xfs_ilock+0x1d8/0x3d0 fs/xfs/xfs_inode.c:165 >> >> which lock already depends on the new lock. > > #syz test This crash does not have a reproducer. I cannot test it. > > > iomap: use mapping_gfp_mask() for iomap_fill_dirty_folios() > > From: Dave Chinner > > GFP_KERNEL allocations in the buffered write path generates false > positive lockdep warnings against inode reclaim such as: > > -> #1 (&xfs_nondir_ilock_class){++++}-{4:4}: > down_write_nested+0x58/0xcc kernel/locking/rwsem.c:1706 > xfs_ilock+0x1d8/0x3d0 fs/xfs/xfs_inode.c:165 > xfs_reclaim_inode fs/xfs/xfs_icache.c:1035 [inline] > xfs_icwalk_process_inode fs/xfs/xfs_icache.c:1727 [inline] > xfs_icwalk_ag+0xe4c/0x16a4 fs/xfs/xfs_icache.c:1809 > xfs_icwalk fs/xfs/xfs_icache.c:1857 [inline] > xfs_reclaim_inodes_nr+0x1b4/0x268 fs/xfs/xfs_icache.c:1101 > xfs_fs_free_cached_objects+0x68/0x7c fs/xfs/xfs_super.c:1282 > super_cache_scan+0x2f0/0x380 fs/super.c:228 > do_shrink_slab+0x638/0x11b0 mm/shrinker.c:437 > shrink_slab+0xc68/0xfb8 mm/shrinker.c:664 > shrink_node_memcgs mm/vmscan.c:6022 [inline] > shrink_node+0xe18/0x20bc mm/vmscan.c:6061 > kswapd_shrink_node mm/vmscan.c:6901 [inline] > balance_pgdat+0xb60/0x13b8 mm/vmscan.c:7084 > kswapd+0x6d0/0xe64 mm/vmscan.c:7354 > kthread+0x5fc/0x75c kernel/kthread.c:463 > ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:844 > > -> #0 (fs_reclaim){+.+.}-{0:0}: > check_prev_add kernel/locking/lockdep.c:3165 [inline] > check_prevs_add kernel/locking/lockdep.c:3284 [inline] > validate_chain kernel/locking/lockdep.c:3908 [inline] > __lock_acquire+0x1774/0x30a4 kernel/locking/lockdep.c:5237 > lock_acquire+0x140/0x2e0 kernel/locking/lockdep.c:5868 > __fs_reclaim_acquire mm/page_alloc.c:4301 [inline] > fs_reclaim_acquire+0x8c/0x118 mm/page_alloc.c:4315 > might_alloc include/linux/sched/mm.h:317 [inline] > slab_pre_alloc_hook mm/slub.c:4904 [inline] > slab_alloc_node mm/slub.c:5239 [inline] > __kmalloc_cache_noprof+0x58/0x698 mm/slub.c:5771 > kmalloc_noprof include/linux/slab.h:957 [inline] > iomap_fill_dirty_folios+0xf0/0x218 fs/iomap/buffered-io.c:1557 > xfs_buffered_write_iomap_begin+0x8b4/0x1668 fs/xfs/xfs_iomap.c:1857 > iomap_iter+0x528/0xefc fs/iomap/iter.c:110 > iomap_zero_range+0x17c/0x8ec fs/iomap/buffered-io.c:1590 > xfs_zero_range+0x98/0xfc fs/xfs/xfs_iomap.c:2289 > xfs_reflink_zero_posteof+0x110/0x2f0 fs/xfs/xfs_reflink.c:1619 > xfs_reflink_remap_prep+0x314/0x5e4 fs/xfs/xfs_reflink.c:1699 > xfs_file_remap_range+0x1f4/0x758 fs/xfs/xfs_file.c:1518 > vfs_clone_file_range+0x62c/0xb68 fs/remap_range.c:403 > ioctl_file_clone fs/ioctl.c:239 [inline] > ioctl_file_clone_range fs/ioctl.c:257 [inline] > do_vfs_ioctl+0xb84/0x1834 fs/ioctl.c:544 > > We use mapping_gfp_mask() in the IO paths where the IOLOCK is held > to avoid these false positives and any possible reclaim recursion > deadlock that might occur from complex nested calls into the IO > path. > > Fixes: 395ed1ef0012 ("iomap: optional zero range dirty folio processing") > Reported-by: syzbot+c628140f24c07eb768d8@syzkaller.appspotmail.com > Signed-off-by: Dave Chinner > --- > fs/iomap/buffered-io.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index e5c1ca440d93..01f0263e285a 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -1554,7 +1554,8 @@ iomap_fill_dirty_folios( > pgoff_t start = offset >> PAGE_SHIFT; > pgoff_t end = (offset + length - 1) >> PAGE_SHIFT; > > - iter->fbatch = kmalloc(sizeof(struct folio_batch), GFP_KERNEL); > + iter->fbatch = kmalloc(sizeof(struct folio_batch), > + mapping_gfp_mask(mapping)); > if (!iter->fbatch) > return offset + length; > folio_batch_init(iter->fbatch);