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Message-ID: <20240805163322.GA17473@twin.jikos.cz>
Date: Mon, 5 Aug 2024 18:33:22 +0200
From: David Sterba <dsterba@...e.cz>
To: Johannes Thumshirn <jth@...nel.org>
Cc: Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org,
linux-kernel@...r.kernel.org,
Johannes Thumshirn <jthumshirn@....com>,
Filipe Manana <fdmanana@...e.com>, Qu Wenruo <wqu@...e.com>,
Johannes Thumshirn <johannes.thumshirn@....com>
Subject: Re: [PATCH v3 4/5] btrfs: don't readahead the relocation inode on RST
On Wed, Jul 31, 2024 at 10:43:06PM +0200, Johannes Thumshirn wrote:
> From: Johannes Thumshirn <jthumshirn@....com>
>
> 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 (e.g. due to
> preallocated extents not being mapped in the RST) 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.
>
> Cc: Josef Bacik <josef@...icpanda.com>
> Cc: Filipe Manana <fdmanana@...e.com>
> Reviewed-by: Josef Bacik <josef@...icpanda.com>
> Reviewed-by: Qu Wenruo <wqu@...e.com>
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@....com>
> ---
> 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 0533d0f82dc9..72fb43b4d27c 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 =
const bool
> + 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,
Please add a comment why readahead is skipped for RST (along the lines
in the changelog).
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