On Mon, Jan 15, 2024 at 09:22:19AM -0800, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 3e7aeb78ab01 Merge tag 'net-next-6.8' of git://git.kernel... > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=13f61d33e80000 > kernel config: https://syzkaller.appspot.com/x/.config?x=8e557b1c0a57d2c0 > dashboard link: https://syzkaller.appspot.com/bug?extid=4a4f1eba14eb5c3417d1 > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16bdfc0be80000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=177f3c83e80000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/4c8a9f091067/disk-3e7aeb78.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/8cb663b518a5/vmlinux-3e7aeb78.xz > kernel image: https://storage.googleapis.com/syzbot-assets/bc6d189cfcf3/bzImage-3e7aeb78.xz > mounted in repro #1: https://storage.googleapis.com/syzbot-assets/e37fd964ba01/mount_0.gz > mounted in repro #2: https://storage.googleapis.com/syzbot-assets/174ce0bdbd5e/mount_4.gz > > The issue was bisected to: > > commit 2b9ac22b12a266eb4fec246a07b504dd4983b16b > Author: Kristian Klausen <kristian@xxxxxxxxxx> > Date: Fri Jun 18 11:51:57 2021 +0000 > > loop: Fix missing discard support when using LOOP_CONFIGURE This only adds proper discard support to loop device so it makes the problem visible. > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=111924a5e80000 > final oops: https://syzkaller.appspot.com/x/report.txt?x=131924a5e80000 > console output: https://syzkaller.appspot.com/x/log.txt?x=151924a5e80000 > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+4a4f1eba14eb5c3417d1@xxxxxxxxxxxxxxxxxxxxxxxxx > Fixes: 2b9ac22b12a2 ("loop: Fix missing discard support when using LOOP_CONFIGURE") > > ------------[ cut here ]------------ > WARNING: CPU: 0 PID: 5071 at fs/btrfs/extent-tree.c:1263 btrfs_issue_discard+0x5ba/0x5e0 fs/btrfs/extent-tree.c:1263 1256 static int btrfs_issue_discard(struct block_device *bdev, u64 start, u64 len, 1257 u64 *discarded_bytes) 1258 { 1259 int j, ret = 0; 1260 u64 bytes_left, end; 1261 u64 aligned_start = ALIGN(start, 1 << SECTOR_SHIFT); 1262 1263 if (WARN_ON(start != aligned_start)) { ^^^^ 1264 len -= aligned_start - start; 1265 len = round_down(len, 1 << SECTOR_SHIFT); 1266 start = aligned_start; 1267 } The alignment check was added in 4d89d377bbb0 ("btrfs: btrfs_issue_discard ensure offset/length are aligned to sector boundaries"), with the WARN_ON. It seems that syzbot is testing unaligned discard requests, which is probably ok but the warning is excessive as there's a fallback.
