From: David Sterba <dsterba@suse.cz>
To: Qu Wenruo <wqu@suse.com>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: [PATCH RFC] btrfs: get rid of btrfs_(alloc|free)_compr_folio()
Date: Thu, 5 Mar 2026 04:09:11 +0100 [thread overview]
Message-ID: <20260305030911.GD5735@suse.cz> (raw)
In-Reply-To: <20260305025611.GC5735@twin.jikos.cz>
On Thu, Mar 05, 2026 at 03:56:11AM +0100, David Sterba wrote:
> On Mon, Mar 02, 2026 at 06:30:30PM +1030, Qu Wenruo wrote:
> > And hopefully this will address David's recent crash (as usual I'm not
> > able to reproduce locally).
>
> I'll run the test with this patch.
Still crashes so the lru is a false hunch.
[ 110.693070] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888100000000 pfn:0x111262
[ 110.694052] flags: 0x4000000000000000(node=0|zone=2)
[ 110.694596] raw: 4000000000000000 ffffea00040f2008 ffffea00042088c8 0000000000000000
[ 110.695383] raw: ffff888100000000 0000000000000000 00000000ffffffff 0000000000000000
[ 110.696164] page dumped because: VM_BUG_ON_PAGE(page_ref_count(page) == 0)
[ 110.696925] ------------[ cut here ]------------
[ 110.697414] kernel BUG at ./include/linux/mm.h:1493!
[ 110.697955] Oops: invalid opcode: 0000 [#1] SMP KASAN
[ 110.698482] CPU: 8 UID: 0 PID: 12 Comm: kworker/u64:0 Not tainted 7.0.0-rc1-default+ #626 PREEMPT(full)
[ 110.699385] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-2-gc13ff2cd-prebuilt.qemu.org 04/01/2014
[ 110.700464] Workqueue: btrfs-delalloc btrfs_work_helper [btrfs]
[ 110.701110] RIP: 0010:btrfs_compress_bio+0x5c2/0x6a0 [btrfs]
[ 110.702716] RSP: 0018:ffff8881003b79a0 EFLAGS: 00010286
[ 110.703082] RAX: 000000000000003e RBX: ffff88810a83d5f8 RCX: 0000000000000000
[ 110.703550] RDX: 000000000000003e RSI: 0000000000000004 RDI: ffffed1020076f27
[ 110.704019] RBP: 1ffff11020076f37 R08: ffffffff8a444651 R09: fffffbfff195c438
[ 110.704484] R10: 0000000000000003 R11: 0000000000000001 R12: ffffea00044498c0
[ 110.704956] R13: ffffea00044498b4 R14: 0000000000000000 R15: ffffea0004449880
[ 110.705555] FS: 0000000000000000(0000) GS:ffff88818baa0000(0000) knlGS:0000000000000000
[ 110.706197] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 110.706664] CR2: 00007f4aa3c715a0 CR3: 0000000097a59000 CR4: 00000000000006b0
[ 110.707131] Call Trace:
[ 110.707335] <TASK>
[ 110.707522] ? btrfs_compress_filemap_get_folio+0x130/0x130 [btrfs]
[ 110.707999] ? _raw_spin_unlock+0x1a/0x30
[ 110.708307] ? btrfs_compress_heuristic+0x48c/0x700 [btrfs]
[ 110.708766] compress_file_range+0x7b7/0x1640 [btrfs]
[ 110.709169] ? cow_file_range_inline.constprop.0+0x1b0/0x1b0 [btrfs]
[ 110.709629] ? __lock_acquire+0x568/0xbd0
[ 110.709934] ? lock_acquire.part.0+0xad/0x230
[ 110.710240] ? process_one_work+0x7ec/0x1590
[ 110.710550] ? submit_one_async_extent+0xb00/0xb00 [btrfs]
[ 110.710970] btrfs_work_helper+0x1c1/0x760 [btrfs]
[ 110.711354] ? lock_acquire+0x128/0x150
[ 110.711635] process_one_work+0x86b/0x1590
[ 110.711934] ? pwq_dec_nr_in_flight+0x720/0x720
[ 110.712255] ? lock_is_held_type+0x83/0xe0
[ 110.712584] worker_thread+0x5e9/0xfc0
[ 110.712869] ? process_one_work+0x1590/0x1590
[ 110.713179] kthread+0x323/0x410
[ 110.713430] ? _raw_spin_unlock_irq+0x1f/0x40
[ 110.713741] ? kthread_affine_node+0x1c0/0x1c0
[ 110.714058] ret_from_fork+0x476/0x5f0
[ 110.714339] ? arch_exit_to_user_mode_prepare.isra.0+0x60/0x60
[ 110.714730] ? __switch_to+0x22/0xe00
[ 110.715011] ? kthread_affine_node+0x1c0/0x1c0
[ 110.715327] ret_from_fork_asm+0x11/0x20
[ 110.715616] </TASK>
[ 110.715806] Modules linked in: btrfs xor raid6_pq loop
[ 110.716186] ---[ end trace 0000000000000000 ]---
[ 110.716538] RIP: 0010:btrfs_compress_bio+0x5c2/0x6a0 [btrfs]
[ 110.718125] RSP: 0018:ffff8881003b79a0 EFLAGS: 00010286
[ 110.718488] RAX: 000000000000003e RBX: ffff88810a83d5f8 RCX: 0000000000000000
[ 110.718958] RDX: 000000000000003e RSI: 0000000000000004 RDI: ffffed1020076f27
[ 110.719448] RBP: 1ffff11020076f37 R08: ffffffff8a444651 R09: fffffbfff195c438
[ 110.719912] R10: 0000000000000003 R11: 0000000000000001 R12: ffffea00044498c0
[ 110.720373] R13: ffffea00044498b4 R14: 0000000000000000 R15: ffffea0004449880
[ 110.720871] FS: 0000000000000000(0000) GS:ffff88818baa0000(0000) knlGS:0000000000000000
[ 110.721409] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 110.721800] CR2: 00007f4aa3c715a0 CR3: 0000000097a59000 CR4: 00000000000006b0
Looks like folio references are wrong, the assert in zlib related to the page
pool was just a symptom and I think actually correct.
The line numbers do not tell anything interesting:
(gdb) l *(btrfs_compress_bio+0x5c2)
0x1f38e2 is in btrfs_compress_bio (./include/linux/mm.h:1493).
1488 /*
1489 * Drop a ref, return true if the refcount fell to zero (the page has no users)
1490 */
1491 static inline int put_page_testzero(struct page *page)
1492 {
1493 VM_BUG_ON_PAGE(page_ref_count(page) == 0, page);
1494 return page_ref_dec_and_test(page);
1495 }
1496
1497 static inline int folio_put_testzero(struct folio *folio)
(gdb) l *(compress_file_range+0x7b7)
0xde947 is in compress_file_range (fs/btrfs/inode.c:1014).
1009 } else if (inode->prop_compress) {
1010 compress_type = inode->prop_compress;
1011 }
1012
1013 /* Compression level is applied here. */
1014 cb = btrfs_compress_bio(inode, start, cur_len, compress_type,
1015 compress_level, async_chunk->write_flags);
1016 if (IS_ERR(cb)) {
1017 cb = NULL;
1018 goto mark_incompressible;
(gdb) l *(btrfs_compress_filemap_get_folio+0x130)
0x1f3320 is in btrfs_compress_bio (fs/btrfs/compression.c:902).
897 * to do the round up before submission.
898 */
899 struct compressed_bio *btrfs_compress_bio(struct btrfs_inode *inode,
900 u64 start, u32 len, unsigned int type,
901 int level, blk_opf_t write_flags)
902 {
903 struct btrfs_fs_info *fs_info = inode->root->fs_info;
904 struct list_head *workspace;
905 struct compressed_bio *cb;
906 int ret;
next prev parent reply other threads:[~2026-03-05 3:09 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-02 8:00 [PATCH RFC] btrfs: get rid of btrfs_(alloc|free)_compr_folio() Qu Wenruo
2026-03-05 2:56 ` David Sterba
2026-03-05 3:09 ` David Sterba [this message]
2026-03-05 4:33 ` Qu Wenruo
2026-03-05 17:46 ` Boris Burkov
2026-03-05 22:43 ` Qu Wenruo
2026-03-05 22:45 ` Boris Burkov
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