[PATCH 4/4] btrfs: don't readahead the relocation inode on RST

[Johannes Thumshirn]

From: Johannes Thumshirn <jthumshirn@xxxxxxx>

On relocation we're doing readahead on the relocation inode, but if the
filesystem is backed by a RAID stripe tree we can get ENOENT from the
lookup.

But readahead doesn't handle the error and submits invalid reads to the
device, causing an assertion in the scatter-gather list code:

  BTRFS info (device nvme1n1): balance: start -d -m -s
  BTRFS info (device nvme1n1): relocating block group 6480920576 flags data|raid0
  BTRFS error (device nvme1n1): cannot find raid-stripe for logical [6481928192, 6481969152] devid 2, profile raid0
  ------------[ cut here ]------------
  kernel BUG at include/linux/scatterlist.h:115!
  Oops: invalid opcode: 0000 [#1] PREEMPT SMP PTI
  CPU: 0 PID: 1012 Comm: btrfs Not tainted 6.10.0-rc7+ #567
  RIP: 0010:__blk_rq_map_sg+0x339/0x4a0
  RSP: 0018:ffffc90001a43820 EFLAGS: 00010202
  RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffea00045d4802
  RDX: 0000000117520000 RSI: 0000000000000000 RDI: ffff8881027d1000
  RBP: 0000000000003000 R08: ffffea00045d4902 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000001000 R12: ffff8881003d10b8
  R13: ffffc90001a438f0 R14: 0000000000000000 R15: 0000000000003000
  FS:  00007fcc048a6900(0000) GS:ffff88813bc00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 000000002cd11000 CR3: 00000001109ea001 CR4: 0000000000370eb0
  Call Trace:
   <TASK>
   ? __die_body.cold+0x14/0x25
   ? die+0x2e/0x50
   ? do_trap+0xca/0x110
   ? do_error_trap+0x65/0x80
   ? __blk_rq_map_sg+0x339/0x4a0
   ? exc_invalid_op+0x50/0x70
   ? __blk_rq_map_sg+0x339/0x4a0
   ? asm_exc_invalid_op+0x1a/0x20
   ? __blk_rq_map_sg+0x339/0x4a0
   nvme_prep_rq.part.0+0x9d/0x770
   nvme_queue_rq+0x7d/0x1e0
   __blk_mq_issue_directly+0x2a/0x90
   ? blk_mq_get_budget_and_tag+0x61/0x90
   blk_mq_try_issue_list_directly+0x56/0xf0
   blk_mq_flush_plug_list.part.0+0x52b/0x5d0
   __blk_flush_plug+0xc6/0x110
   blk_finish_plug+0x28/0x40
   read_pages+0x160/0x1c0
   page_cache_ra_unbounded+0x109/0x180
   relocate_file_extent_cluster+0x611/0x6a0
   ? btrfs_search_slot+0xba4/0xd20
   ? balance_dirty_pages_ratelimited_flags+0x26/0xb00
   relocate_data_extent.constprop.0+0x134/0x160
   relocate_block_group+0x3f2/0x500
   btrfs_relocate_block_group+0x250/0x430
   btrfs_relocate_chunk+0x3f/0x130
   btrfs_balance+0x71b/0xef0
   ? kmalloc_trace_noprof+0x13b/0x280
   btrfs_ioctl+0x2c2e/0x3030
   ? kvfree_call_rcu+0x1e6/0x340
   ? list_lru_add_obj+0x66/0x80
   ? mntput_no_expire+0x3a/0x220
   __x64_sys_ioctl+0x96/0xc0
   do_syscall_64+0x54/0x110
   entry_SYSCALL_64_after_hwframe+0x76/0x7e
  RIP: 0033:0x7fcc04514f9b
  Code: Unable to access opcode bytes at 0x7fcc04514f71.
  RSP: 002b:00007ffeba923370 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
  RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fcc04514f9b
  RDX: 00007ffeba923460 RSI: 00000000c4009420 RDI: 0000000000000003
  RBP: 0000000000000000 R08: 0000000000000013 R09: 0000000000000001
  R10: 00007fcc043fbba8 R11: 0000000000000246 R12: 00007ffeba924fc5
  R13: 00007ffeba923460 R14: 0000000000000002 R15: 00000000004d4bb0
   </TASK>
  Modules linked in:
  ---[ end trace 0000000000000000 ]---
  RIP: 0010:__blk_rq_map_sg+0x339/0x4a0
  RSP: 0018:ffffc90001a43820 EFLAGS: 00010202
  RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffea00045d4802
  RDX: 0000000117520000 RSI: 0000000000000000 RDI: ffff8881027d1000
  RBP: 0000000000003000 R08: ffffea00045d4902 R09: 0000000000000000
  R10: 0000000000000000 R11: 0000000000001000 R12: ffff8881003d10b8
  R13: ffffc90001a438f0 R14: 0000000000000000 R15: 0000000000003000
  FS:  00007fcc048a6900(0000) GS:ffff88813bc00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 00007fcc04514f71 CR3: 00000001109ea001 CR4: 0000000000370eb0
  Kernel panic - not syncing: Fatal exception
  Kernel Offset: disabled
  ---[ end Kernel panic - not syncing: Fatal exception ]---

So in case of a relocation on a RAID stripe-tree based file system, skip
the readahead.

Signed-off-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
Cc: Josef Bacik <josef@xxxxxxxxxxxxxx>
Cc: Filipe Manana <fdmanana@xxxxxxxx>
---
 fs/btrfs/relocation.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index b592fc8cf368..5a6066f6db42 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -36,6 +36,7 @@
 #include "relocation.h"
 #include "super.h"
 #include "tree-checker.h"
+#include "raid-stripe-tree.h"
 
 /*
  * Relocation overview
@@ -2965,21 +2966,26 @@ static int relocate_one_folio(struct reloc_control *rc,
 	u64 folio_end;
 	u64 cur;
 	int ret;
+	bool use_rst =
+		btrfs_need_stripe_tree_update(fs_info, rc->block_group->flags);
 
 	ASSERT(index <= last_index);
 	folio = filemap_lock_folio(inode->i_mapping, index);
 	if (IS_ERR(folio)) {
-		page_cache_sync_readahead(inode->i_mapping, ra, NULL,
-					  index, last_index + 1 - index);
+		if (!use_rst)
+			page_cache_sync_readahead(inode->i_mapping, ra, NULL,
+						  index,
+						  last_index + 1 - index);
 		folio = __filemap_get_folio(inode->i_mapping, index,
-					    FGP_LOCK | FGP_ACCESSED | FGP_CREAT, mask);
+					    FGP_LOCK | FGP_ACCESSED | FGP_CREAT,
+					    mask);
 		if (IS_ERR(folio))
 			return PTR_ERR(folio);
 	}
 
 	WARN_ON(folio_order(folio));
 
-	if (folio_test_readahead(folio))
+	if (folio_test_readahead(folio) && !use_rst)
 		page_cache_async_readahead(inode->i_mapping, ra, NULL,
 					   folio, index,
 					   last_index + 1 - index);

-- 
2.43.0