xfs: fix warning in xfs_vm_writepages()

Offering: HULK
hulk inclusion
category: bugfix
bugzilla: 188782, https://gitee.com/openeuler/kernel/issues/I76JSK

-----------------------------------------------

When do BULKSTAT test got issues as follows:
WARNING: CPU: 3 PID: 8425 at fs/xfs/xfs_aops.c:509 xfs_vm_writepages+0x184/0x1c0
Modules linked in:
CPU: 3 PID: 8425 Comm: xfs_bulkstat Not tainted 6.3.0-next-20230505-00003-gf3329adf5424-dirty #456
RIP: 0010:xfs_vm_writepages+0x184/0x1c0
RSP: 0018:ffffc90014bb7088 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 1ffff92002976e11 RCX: ffff88817aef8000
RDX: 0000000000000000 RSI: ffff88817aef8000 RDI: 0000000000000002
RBP: ffff888267dd2ad8 R08: ffffffff8313f414 R09: ffffed1022377c18
R10: ffff888111bbe0bb R11: ffffed1022377c17 R12: ffff88817aef8000
R13: ffffc90014bb7358 R14: dffffc0000000000 R15: ffffffff8313f290
FS:  00007f9568bb0440(0000) GS:ffff88882fc80000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000d7a008 CR3: 000000024e11f000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 do_writepages+0x1a8/0x630
 __writeback_single_inode+0x126/0xe00
 writeback_single_inode+0x2ae/0x530
 write_inode_now+0x16e/0x1e0
 iput.part.0+0x46c/0x730
 iput+0x60/0x80
 xfs_bulkstat_one_int+0xd87/0x1580
 xfs_bulkstat_iwalk+0x6e/0xd0
 xfs_iwalk_ag_recs+0x449/0x770
 xfs_iwalk_run_callbacks+0x305/0x630
 xfs_iwalk_ag+0x819/0xae0
 xfs_iwalk+0x2d5/0x4e0
 xfs_bulkstat+0x358/0x520
 xfs_ioc_bulkstat.isra.0+0x242/0x340
 xfs_file_ioctl+0x1d6/0x1ba0
 __x64_sys_ioctl+0x197/0x210
 do_syscall_64+0x39/0xb0
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Above issue may happens as follows:
Porcess1          Process2           process3         process4
xfs_bulkstat
 xfs_trans_alloc_empty
 xfs_bulkstat_one_int
   xfs_iget(XFS_IGET_DONTCACHE)
   ->Get inode from disk and mark
     inode with I_DONTCACHE

                                                     xfs_lookup
                                                       xfs_iget
                                                       ->Hold inode refcount
   xfs_irele

                 xfs_file_write_iter
                 ->Write file made some dirty pages
                 close file

                                    xfs_bulkstat
                                      xfs_trans_alloc_empty
                                      xfs_bulkstat_one_int
                                        xfs_iget(XFS_IGET_DONTCACHE)

                                                       -> process4 close file

        ******Trigger dentry reclaim, inode refcount is 1******
                                        xfs_irele
                                          iput ->Put the last refcount
                                            iput_final
                                              write_inode_now
                                                xfs_vm_writepages
                                                  WARN_ON_ONCE(current->journal_info)
                                                  ->Trigger warning

As commit a6343e4d grab an empty transaction when do BULKSTAT. If put
the last refcount of inode maybe cause writepages will trigger warning, and
also lead to data loss.
To solve above issue if xfs_iget_cache_hit() just clear inode's I_DONTCACHE
flags.

Fixes: a6343e4d ("xfs: avoid buffer deadlocks when walking fs inodes")
Signed-off-by: NYe Bin <yebin10@huawei.com>
Signed-off-by: NLong Li <leo.lilong@huawei.com>
(cherry picked from commit 28ce0ae2)

fs/xfs/xfs_icache.c

@@ -534,6 +534,12 @@ xfs_iget_cache_hit(
 		if (!igrab(inode))
 			goto out_skip;
 
+		if (!(flags & XFS_IGET_DONTCACHE)) {
+			spin_lock(&inode->i_lock);
+			inode->i_state &= ~I_DONTCACHE;
+			spin_unlock(&inode->i_lock);
+		}
+
 		/* We've got a live one. */
 		spin_unlock(&ip->i_flags_lock);
 		rcu_read_unlock();