[PATCHv4 1/1] xfs: Add cond_resched to block unmap range and reflink remap path

["Ritesh Harjani (IBM)" <ritesh.list@gmail.com>]

An async dio write to a sparse file can generate a lot of extents
and when we unlink this file (using rm), the kernel can be busy in umapping
and freeing those extents as part of transaction processing.

Similarly xfs reflink remapping path can also iterate over a million
extent entries in xfs_reflink_remap_blocks().

Since we can busy loop in these two functions, so let's add cond_resched()
to avoid softlockup messages like these.

watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [kworker/1:0:82435]
CPU: 1 PID: 82435 Comm: kworker/1:0 Tainted: G S  L   6.9.0-rc5-0-default #1
Workqueue: xfs-inodegc/sda2 xfs_inodegc_worker
NIP [c000000000beea10] xfs_extent_busy_trim+0x100/0x290
LR [c000000000bee958] xfs_extent_busy_trim+0x48/0x290
Call Trace:
  xfs_alloc_get_rec+0x54/0x1b0 (unreliable)
  xfs_alloc_compute_aligned+0x5c/0x144
  xfs_alloc_ag_vextent_size+0x238/0x8d4
  xfs_alloc_fix_freelist+0x540/0x694
  xfs_free_extent_fix_freelist+0x84/0xe0
  __xfs_free_extent+0x74/0x1ec
  xfs_extent_free_finish_item+0xcc/0x214
  xfs_defer_finish_one+0x194/0x388
  xfs_defer_finish_noroll+0x1b4/0x5c8
  xfs_defer_finish+0x2c/0xc4
  xfs_bunmapi_range+0xa4/0x100
  xfs_itruncate_extents_flags+0x1b8/0x2f4
  xfs_inactive_truncate+0xe0/0x124
  xfs_inactive+0x30c/0x3e0
  xfs_inodegc_worker+0x140/0x234
  process_scheduled_works+0x240/0x57c
  worker_thread+0x198/0x468
  kthread+0x138/0x140
  start_kernel_thread+0x14/0x18

run fstests generic/175 at 2024-02-02 04:40:21
[   C17] watchdog: BUG: soft lockup - CPU#17 stuck for 23s! [xfs_io:7679]
 watchdog: BUG: soft lockup - CPU#17 stuck for 23s! [xfs_io:7679]
 CPU: 17 PID: 7679 Comm: xfs_io Kdump: loaded Tainted: G X 6.4.0
 NIP [c008000005e3ec94] xfs_rmapbt_diff_two_keys+0x54/0xe0 [xfs]
 LR [c008000005e08798] xfs_btree_get_leaf_keys+0x110/0x1e0 [xfs]
 Call Trace:
  0xc000000014107c00 (unreliable)
  __xfs_btree_updkeys+0x8c/0x2c0 [xfs]
  xfs_btree_update_keys+0x150/0x170 [xfs]
  xfs_btree_lshift+0x534/0x660 [xfs]
  xfs_btree_make_block_unfull+0x19c/0x240 [xfs]
  xfs_btree_insrec+0x4e4/0x630 [xfs]
  xfs_btree_insert+0x104/0x2d0 [xfs]
  xfs_rmap_insert+0xc4/0x260 [xfs]
  xfs_rmap_map_shared+0x228/0x630 [xfs]
  xfs_rmap_finish_one+0x2d4/0x350 [xfs]
  xfs_rmap_update_finish_item+0x44/0xc0 [xfs]
  xfs_defer_finish_noroll+0x2e4/0x740 [xfs]
  __xfs_trans_commit+0x1f4/0x400 [xfs]
  xfs_reflink_remap_extent+0x2d8/0x650 [xfs]
  xfs_reflink_remap_blocks+0x154/0x320 [xfs]
  xfs_file_remap_range+0x138/0x3a0 [xfs]
  do_clone_file_range+0x11c/0x2f0
  vfs_clone_file_range+0x60/0x1c0
  ioctl_file_clone+0x78/0x140
  sys_ioctl+0x934/0x1270
  system_call_exception+0x158/0x320
  system_call_vectored_common+0x15c/0x2ec

Cc: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
---
 fs/xfs/libxfs/xfs_bmap.c | 1 +
 fs/xfs/xfs_reflink.c     | 1 +
 2 files changed, 2 insertions(+)

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 656c95a22f2e..44d5381bc66f 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -6354,6 +6354,7 @@ xfs_bunmapi_range(
 		error = xfs_defer_finish(tpp);
 		if (error)
 			goto out;
+		cond_resched();
 	}
 out:
 	return error;
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 7da0e8f961d3..5f26a608bc09 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1417,6 +1417,7 @@ xfs_reflink_remap_blocks(
 		destoff += imap.br_blockcount;
 		len -= imap.br_blockcount;
 		remapped_len += imap.br_blockcount;
+		cond_resched();
 	}

 	if (error)
--
2.44.0