Hi Xuenan, (+ Cc Darrick.. ) On Tue, Mar 15, 2022 at 02:57:45PM +0800, Guo Xuenan wrote: > when get fiemap starting from MAX_LFS_FILESIZE, (maxbytes - *len) < start > will always true , then *len set zero. because of start offset is byhond > file size, for erofs filesystem it will always return iomap.length with > zero,iomap iterate will be infinite loop. Thanks! If my understanding is correct, we once had a similar behavior in compressed inodes and it has been worked around with https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/erofs/zmap.c?h=v5.17-rc8#n762 But yeah, if iomap can define or handle post-EOF extent length behavior exactly, it would be much better! So on my side, Reviewed-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx> (Also you might need to inform iomap maintainer Darrick as well..) Thanks, Gao Xiang > > In order to avoid this situation, it is better to calculate the actual > mapping length at first. If the len is 0, there is no need to continue > the operation. > > ------------[ cut here ]------------ > WARNING: CPU: 7 PID: 905 at fs/iomap/iter.c:35 iomap_iter+0x97f/0xc70 > Modules linked in: xfs erofs > CPU: 7 PID: 905 Comm: iomap Tainted: G W 5.17.0-rc8 #27 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 > RIP: 0010:iomap_iter+0x97f/0xc70 > Code: 85 a1 fc ff ff e8 71 be 9c ff 0f 1f 44 00 00 e9 92 fc ff ff e8 62 be 9c ff 0f 0b b8 fb ff ff ff e9 fc f8 ff ff e8 51 be 9c ff <0f> 0b e9 2b fc ff ff e8 45 be 9c ff 0f 0b e9 e1 fb ff ff e8 39 be > RSP: 0018:ffff888060a37ab0 EFLAGS: 00010293 > RAX: 0000000000000000 RBX: ffff888060a37bb0 RCX: 0000000000000000 > RDX: ffff88807e19a900 RSI: ffffffff81a7da7f RDI: ffff888060a37be0 > RBP: 7fffffffffffffff R08: 0000000000000000 R09: ffff888060a37c20 > R10: ffff888060a37c67 R11: ffffed100c146f8c R12: 7fffffffffffffff > R13: 0000000000000000 R14: ffff888060a37bd8 R15: ffff888060a37c20 > FS: 00007fd3cca01540(0000) GS:ffff888108780000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000020010820 CR3: 0000000054b92000 CR4: 00000000000006e0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > <TASK> > iomap_fiemap+0x1c9/0x2f0 > erofs_fiemap+0x64/0x90 [erofs] > do_vfs_ioctl+0x40d/0x12e0 > __x64_sys_ioctl+0xaa/0x1c0 > do_syscall_64+0x35/0x80 > entry_SYSCALL_64_after_hwframe+0x44/0xae > </TASK> > ---[ end trace 0000000000000000 ]--- > watchdog: BUG: soft lockup - CPU#7 stuck for 26s! [iomap:905] > > Reported-by: Hulk Robot <hulkci@xxxxxxxxxx> > Signed-off-by: Guo Xuenan <guoxuenan@xxxxxxxxxx> > --- > fs/ioctl.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/fs/ioctl.c b/fs/ioctl.c > index 1ed097e94af2..7f70e90766ed 100644 > --- a/fs/ioctl.c > +++ b/fs/ioctl.c > @@ -171,8 +171,6 @@ int fiemap_prep(struct inode *inode, struct fiemap_extent_info *fieinfo, > u32 incompat_flags; > int ret = 0; > > - if (*len == 0) > - return -EINVAL; > if (start > maxbytes) > return -EFBIG; > > @@ -182,6 +180,9 @@ int fiemap_prep(struct inode *inode, struct fiemap_extent_info *fieinfo, > if (*len > maxbytes || (maxbytes - *len) < start) > *len = maxbytes - start; > > + if (*len == 0) > + return -EINVAL; > + > supported_flags |= FIEMAP_FLAG_SYNC; > supported_flags &= FIEMAP_FLAGS_COMPAT; > incompat_flags = fieinfo->fi_flags & ~supported_flags; > -- > 2.22.0
