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Message-ID: <9365db29-dc4a-44a5-b90b-721a546d28c2@squashfs.org.uk>
Date: Fri, 20 Dec 2024 18:19:24 +0000
From: Phillip Lougher <phillip@...ashfs.org.uk>
To: "Matthew Wilcox (Oracle)" <willy@...radead.org>
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 5/5] squashfs: Convert squashfs_fill_page() to take a
folio
On 16/12/2024 16:26, Matthew Wilcox (Oracle) wrote:
> squashfs_fill_page is only used in this file, so make it static.
> Use kmap_local instead of kmap_atomic, and return a bool so that
> the caller can use folio_end_read() which saves an atomic operation
> over calling folio_mark_uptodate() followed by folio_unlock().
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Hi Matthew,
This patch causes 2 oops (VM_BUG_ON_FOLIO).
The cause and fix for the first oops follows (second oops in the next
email).
> ---
> fs/squashfs/file.c | 21 ++++++++++++---------
> fs/squashfs/squashfs.h | 1 -
> 2 files changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/fs/squashfs/file.c b/fs/squashfs/file.c
> index 1f27e8161319..d363fb26c2c8 100644
> --- a/fs/squashfs/file.c
> +++ b/fs/squashfs/file.c
> @@ -362,19 +362,21 @@ static int read_blocklist(struct inode *inode, int index, u64 *block)
> return squashfs_block_size(size);
> }
>
> -void squashfs_fill_page(struct page *page, struct squashfs_cache_entry *buffer, int offset, int avail)
> +static bool squashfs_fill_page(struct folio *folio,
> + struct squashfs_cache_entry *buffer, size_t offset,
> + size_t avail)
> {
> - int copied;
> + size_t copied;
> void *pageaddr;
>
> - pageaddr = kmap_atomic(page);
> + pageaddr = kmap_local_folio(folio, 0);
> copied = squashfs_copy_data(pageaddr, buffer, offset, avail);
> memset(pageaddr + copied, 0, PAGE_SIZE - copied);
> - kunmap_atomic(pageaddr);
> + kunmap_local(pageaddr);
>
> - flush_dcache_page(page);
> - if (copied == avail)
> - SetPageUptodate(page);
> + flush_dcache_folio(folio);
> +
> + return copied == avail;
> }
>
> /* Copy data into page cache */
> @@ -398,6 +400,7 @@ void squashfs_copy_cache(struct folio *folio,
> bytes -= PAGE_SIZE, offset += PAGE_SIZE) {
> struct folio *push_folio;
> size_t avail = buffer ? min(bytes, PAGE_SIZE) : 0;
> + bool filled = false;
>
> TRACE("bytes %zu, i %d, available_bytes %zu\n", bytes, i, avail);
>
> @@ -412,9 +415,9 @@ void squashfs_copy_cache(struct folio *folio,
> if (folio_test_uptodate(push_folio))
> goto skip_folio;
>
> - squashfs_fill_page(&push_folio->page, buffer, offset, avail);
> + filled = squashfs_fill_page(push_folio, buffer, offset, avail);
> skip_folio:
> - folio_unlock(push_folio);
> + folio_end_read(folio, filled);
This should be
folio_end_read(push_folio, filled)
Without this folio_end_read() is repeatedly called on folio,
generating the following oops
[ 187.271288][ T8043] page: refcount:2 mapcount:0 mapping:ffff888116ae0798 index:0x100 pfn:0x1296c7
[ 187.272129][ T8043] memcg:ffff8881016cc000
[ 187.272458][ T8043] aops:squashfs_aops ino:1b dentry name(?):".tmp_vmlinux1"
[ 187.273013][ T8043] flags: 0x4000000000000028(uptodate|lru|zone=2)
[ 187.273500][ T8043] raw: 4000000000000028 ffffea0004655308 ffffea0004ac2e08 ffff888116ae0798
[ 187.274160][ T8043] raw: 0000000000000100 0000000000000000 00000002ffffffff ffff8881016cc000
[ 187.274809][ T8043] page dumped because: VM_BUG_ON_FOLIO(!folio_test_locked(folio))
[ 187.275348][ T8043] page_owner tracks the page as allocated
[ 187.275787][ T8043] page last allocated via order 0, migratetype Movable, gfp_mask 0x152c4a(GFP_N0
[ 187.277262][ T8043] post_alloc_hook+0x2d0/0x350
[ 187.277586][ T8043] get_page_from_freelist+0xb39/0x22a0
[ 187.277941][ T8043] __alloc_pages_noprof+0x1bc/0x480
[ 187.278279][ T8043] __folio_alloc_noprof+0x11/0x90
[ 187.278600][ T8043] page_cache_ra_unbounded+0x2e3/0x750
[ 187.278939][ T8043] page_cache_ra_order+0x8ef/0xc30
[ 187.279252][ T8043] page_cache_async_ra+0x5cb/0x820
[ 187.279567][ T8043] filemap_get_pages+0x105b/0x1bd0
[ 187.279880][ T8043] filemap_read+0x3b6/0xd50
[ 187.280157][ T8043] generic_file_read_iter+0x344/0x450
[ 187.280481][ T8043] __kernel_read+0x3b5/0xb10
[ 187.280774][ T8043] integrity_kernel_read+0x7f/0xb0
[ 187.281091][ T8043] ima_calc_file_hash_tfm+0x2bc/0x3d0
[ 187.281425][ T8043] ima_calc_file_hash+0x1ba/0x490
[ 187.281756][ T8043] ima_collect_measurement+0x848/0x9d0
[ 187.282088][ T8043] process_measurement+0x126b/0x2390
[ 187.282409][ T8043] page last free pid 4949 tgid 4949 stack trace:
[ 187.282788][ T8043] free_unref_folios+0x8ea/0x13e0
[ 187.283095][ T8043] folios_put_refs+0x589/0x7b0
[ 187.283386][ T8043] free_pages_and_swap_cache+0x23d/0x490
[ 187.283727][ T8043] __tlb_batch_free_encoded_pages+0xf9/0x290
[ 187.284115][ T8043] tlb_finish_mmu+0x168/0x7b0
[ 187.284438][ T8043] vms_clear_ptes.part.0+0x4b7/0x690
[ 187.284853][ T8043] vms_complete_munmap_vmas+0x6c3/0x9e0
[ 187.285276][ T8043] do_vmi_align_munmap+0x600/0x870
[ 187.285679][ T8043] __do_sys_brk+0x888/0xa50
[ 187.286001][ T8043] do_syscall_64+0x74/0x1c0
[ 187.286325][ T8043] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 187.286768][ T8043] ------------[ cut here ]------------
[ 187.287114][ T8043] kernel BUG at mm/filemap.c:1534!
[ 187.287464][ T8043] Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
[ 187.287979][ T8043] CPU: 13 UID: 0 PID: 8043 Comm: wc Not tainted 6.13.0-rc2-00368-g673506e97177 5
[ 187.288717][ T8043] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.24
[ 187.289495][ T8043] RIP: 0010:folio_end_read+0x165/0x1a0
[ 187.289910][ T8043] Code: 89 ef 31 f6 e8 1c c6 ff ff 5b 5d 41 5c 41 5d 41 5e e9 1f 62 ca ff e8 1a0
[ 187.291452][ T8043] RSP: 0018:ffffc9000a0cea00 EFLAGS: 00010293
[ 187.291867][ T8043] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc9000a0ce8a8
[ 187.292442][ T8043] RDX: ffff888118375880 RSI: ffffffff81cd65a5 RDI: ffff888118375cc4
[ 187.293006][ T8043] RBP: ffffea0004a5b1c0 R08: 0000000000000000 R09: fffffbfff1efaefa
[ 187.293632][ T8043] R10: ffffffff8f7d77d7 R11: 0000000000000001 R12: 0000000000000001
[ 187.294228][ T8043] R13: 0000000000000001 R14: 0000000000000101 R15: ffffea0004a5b1c0
[ 187.294808][ T8043] FS: 00007f2509ad0700(0000) GS:ffff888159480000(0000) knlGS:0000000000000000
[ 187.295485][ T8043] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 187.295993][ T8043] CR2: 00007fff92c60000 CR3: 0000000124c28000 CR4: 00000000003506f0
[ 187.296600][ T8043] Call Trace:
[ 187.296837][ T8043] <TASK>
[ 187.297052][ T8043] ? die+0x31/0x80
[ 187.297332][ T8043] ? do_trap+0x232/0x430
[ 187.297668][ T8043] ? folio_end_read+0x165/0x1a0
[ 187.298045][ T8043] ? folio_end_read+0x165/0x1a0
[ 187.298414][ T8043] ? do_error_trap+0xf4/0x230
[ 187.298741][ T8043] ? folio_end_read+0x165/0x1a0
[ 187.299130][ T8043] ? handle_invalid_op+0x34/0x40
[ 187.299442][ T8043] ? folio_end_read+0x165/0x1a0
[ 187.299748][ T8043] ? exc_invalid_op+0x2d/0x40
[ 187.300104][ T8043] ? asm_exc_invalid_op+0x1a/0x20
[ 187.300487][ T8043] ? folio_end_read+0x165/0x1a0
[ 187.300821][ T8043] ? folio_end_read+0x165/0x1a0
[ 187.301164][ T8043] squashfs_copy_cache+0x1d4/0x540
[ 187.301532][ T8043] squashfs_read_folio+0xa13/0xc00
[ 187.301869][ T8043] ? __pfx_squashfs_read_folio+0x10/0x10
[ 187.302219][ T8043] ? __pfx_squashfs_read_folio+0x10/0x10
[ 187.302566][ T8043] filemap_read_folio+0xc0/0x2a0
[ 187.302886][ T8043] ? __pfx_filemap_read_folio+0x10/0x10
[ 187.303257][ T8043] ? page_cache_async_ra+0x5cb/0x820
[ 187.303624][ T8043] filemap_get_pages+0x155c/0x1bd0
[ 187.303968][ T8043] ? __pfx_make_vfsgid+0x10/0x10
[ 187.304279][ T8043] ? __pfx_filemap_get_pages+0x10/0x10
[ 187.304626][ T8043] filemap_read+0x3b6/0xd50
[ 187.304944][ T8043] ? __pfx_filemap_read+0x10/0x10
[ 187.305280][ T8043] ? kernel_text_address+0x8d/0x100
[ 187.305643][ T8043] ? pvh_start_xen+0x1/0x108
[ 187.305964][ T8043] ? __kernel_text_address+0xd/0x40
[ 187.306309][ T8043] ? unwind_get_return_address+0x59/0xa0
[ 187.306697][ T8043] ? __pfx_stack_trace_consume_entry+0x10/0x10
[ 187.307104][ T8043] ? arch_stack_walk+0x9d/0xf0
[ 187.307413][ T8043] ? stack_trace_save+0x95/0xd0
[ 187.307737][ T8043] ? __pfx_stack_trace_save+0x10/0x10
[ 187.308133][ T8043] ? stack_depot_save_flags+0x28/0x9d0
[ 187.308652][ T8043] generic_file_read_iter+0x344/0x450
[ 187.309054][ T8043] __kernel_read+0x3b5/0xb10
[ 187.309430][ T8043] ? __pfx___kernel_read+0x10/0x10
[ 187.309855][ T8043] integrity_kernel_read+0x7f/0xb0
[ 187.310279][ T8043] ? __pfx_integrity_kernel_read+0x10/0x10
[ 187.310737][ T8043] ? _sha256_update+0x93/0x220
[ 187.311140][ T8043] ? __pfx_sha256_transform_rorx+0x10/0x10
[ 187.311579][ T8043] ? kasan_save_track+0x14/0x30
[ 187.311956][ T8043] ima_calc_file_hash_tfm+0x2bc/0x3d0
[ 187.312362][ T8043] ? __pfx_ima_calc_file_hash_tfm+0x10/0x10
[ 187.312780][ T8043] ? squashfs_xattr_handler_get+0x522/0x6c0
[ 187.313171][ T8043] ? vfs_getxattr_alloc+0x1b9/0x340
[ 187.313541][ T8043] ? ima_read_xattr+0x38/0x60
[ 187.313868][ T8043] ? process_measurement+0x11e2/0x2390
[ 187.314237][ T8043] ? ima_file_check+0xb4/0x100
[ 187.314556][ T8043] ? security_file_post_open+0x8e/0x210
[ 187.314933][ T8043] ? path_openat+0x13f9/0x2d50
[ 187.315261][ T8043] ? mark_lock+0x101/0x1780
[ 187.315558][ T8043] ? entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 187.315949][ T8043] ? mark_held_locks+0x9f/0xe0
[ 187.316266][ T8043] ? __pfx_mark_lock+0x10/0x10
[ 187.316590][ T8043] ? lockdep_hardirqs_on+0x7c/0x100
[ 187.317283][ T8043] ? _raw_spin_unlock_irqrestore+0x3b/0x80
[ 187.317722][ T8043] ? debug_check_no_obj_freed+0x2eb/0x5c0
[ 187.318090][ T8043] ? make_vfsgid+0xf2/0x140
[ 187.318389][ T8043] ? __pfx_make_vfsgid+0x10/0x10
[ 187.318719][ T8043] ? __pfx_debug_check_no_obj_freed+0x10/0x10
[ 187.319113][ T8043] ? ima_alloc_tfm+0x21d/0x2d0
[ 187.319430][ T8043] ? generic_fillattr+0x6bf/0x940
[ 187.319762][ T8043] ima_calc_file_hash+0x1ba/0x490
[ 187.320096][ T8043] ima_collect_measurement+0x848/0x9d0
[ 187.320459][ T8043] ? __pfx_ima_collect_measurement+0x10/0x10
[ 187.320855][ T8043] ? squashfs_xattr_handler_get+0x527/0x6c0
[ 187.321253][ T8043] ? process_measurement+0x86d/0x2390
[ 187.321630][ T8043] ? find_held_lock+0x2d/0x110
[ 187.321973][ T8043] ? xattr_resolve_name+0x27b/0x3f0
[ 187.322333][ T8043] ? __pfx_squashfs_xattr_handler_get+0x10/0x10
[ 187.322762][ T8043] ? vfs_getxattr_alloc+0xf1/0x340
[ 187.323118][ T8043] ? ima_get_hash_algo+0x27d/0x410
[ 187.323474][ T8043] ? __pfx_ima_get_hash_algo+0x10/0x10
[ 187.323895][ T8043] ? process_measurement+0x126b/0x2390
[ 187.324268][ T8043] process_measurement+0x126b/0x2390
[ 187.324661][ T8043] ? __pfx_process_measurement+0x10/0x10
[ 187.325046][ T8043] ? tomoyo_check_open_permission+0x1f0/0x3a0
[ 187.325463][ T8043] ? __pfx_smack_log+0x10/0x10
[ 187.325796][ T8043] ? smk_access+0x39a/0x5e0
[ 187.326105][ T8043] ? smk_tskacc+0x340/0x430
[ 187.326409][ T8043] ? smack_file_open+0x1c1/0x250
[ 187.326741][ T8043] ? __pfx_smack_file_open+0x10/0x10
[ 187.327087][ T8043] ? inode_to_bdi+0x9e/0x160
[ 187.327389][ T8043] ima_file_check+0xb4/0x100
[ 187.327687][ T8043] ? __pfx_ima_file_check+0x10/0x10
[ 187.328056][ T8043] security_file_post_open+0x8e/0x210
[ 187.328427][ T8043] path_openat+0x13f9/0x2d50
[ 187.328740][ T8043] ? __pfx_path_openat+0x10/0x10
[ 187.329057][ T8043] ? __pfx___lock_acquire+0x10/0x10
[ 187.329402][ T8043] ? lock_acquire+0x1b1/0x550
[ 187.329732][ T8043] ? find_held_lock+0x2d/0x110
[ 187.330052][ T8043] do_filp_open+0x1f8/0x460
[ 187.330343][ T8043] ? __pfx_do_filp_open+0x10/0x10
[ 187.330666][ T8043] ? find_held_lock+0x2d/0x110
[ 187.330979][ T8043] ? do_raw_spin_lock+0x12d/0x2b0
[ 187.331318][ T8043] ? __pfx_do_raw_spin_lock+0x10/0x10
[ 187.331661][ T8043] ? __phys_addr_symbol+0x30/0x70
[ 187.331999][ T8043] ? __check_object_size+0x4f7/0x7d0
[ 187.332349][ T8043] ? _raw_spin_unlock+0x28/0x50
[ 187.332662][ T8043] ? alloc_fd+0x41f/0x760
[ 187.332963][ T8043] do_sys_openat2+0x160/0x1c0
[ 187.333296][ T8043] ? __pfx_do_sys_openat2+0x10/0x10
[ 187.333655][ T8043] ? kmem_cache_free+0x39e/0x5b0
[ 187.333979][ T8043] ? security_file_free+0xb9/0x180
[ 187.334304][ T8043] ? __fput+0x686/0xb60
[ 187.334561][ T8043] __x64_sys_open+0x154/0x1e0
[ 187.334855][ T8043] ? __pfx___x64_sys_open+0x10/0x10
[ 187.335209][ T8043] do_syscall_64+0x74/0x1c0
[ 187.335503][ T8043] entry_SYSCALL_64_after_hwframe+0x76/0x7e
[ 187.335882][ T8043] RIP: 0033:0x7f25094db960
[ 187.336176][ T8043] Code: 48 8b 15 2b 95 2c 00 f7 d8 64 89 02 48 83 c8 ff c3 66 0f 1f 84 00 00 004
[ 187.337420][ T8043] RSP: 002b:00007fff92c63888 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
[ 187.337967][ T8043] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f25094db960
[ 187.338505][ T8043] RDX: 00007f2509a74e50 RSI: 0000000000000000 RDI: 00007fff92c6a173
[ 187.339015][ T8043] RBP: 00007fff92c6a173 R08: 6f2e736d79736c6c R09: 00007f250944b99a
[ 187.339511][ T8043] R10: 00007f25097a46a0 R11: 0000000000000246 R12: 00007f2509a74e50
[ 187.340044][ T8043] R13: 0000000000000993 R14: 0000000000000001 R15: 00007fff92c6a173
[ 187.340523][ T8043] </TASK>
[ 187.340707][ T8043] Modules linked in:
[ 187.340976][ T8043] ---[ end trace 0000000000000000 ]---
[ 187.341417][ T8043] RIP: 0010:folio_end_read+0x165/0x1a0
[ 187.341807][ T8043] Code: 89 ef 31 f6 e8 1c c6 ff ff 5b 5d 41 5c 41 5d 41 5e e9 1f 62 ca ff e8 1a0
[ 187.343080][ T8043] RSP: 0018:ffffc9000a0cea00 EFLAGS: 00010293
[ 187.343461][ T8043] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc9000a0ce8a8
[ 187.343989][ T8043] RDX: ffff888118375880 RSI: ffffffff81cd65a5 RDI: ffff888118375cc4
[ 187.344527][ T8043] RBP: ffffea0004a5b1c0 R08: 0000000000000000 R09: fffffbfff1efaefa
[ 187.345049][ T8043] R10: ffffffff8f7d77d7 R11: 0000000000000001 R12: 0000000000000001
[ 187.345598][ T8043] R13: 0000000000000001 R14: 0000000000000101 R15: ffffea0004a5b1c0
[ 187.346144][ T8043] FS: 00007f2509ad0700(0000) GS:ffff888159480000(0000) knlGS:0000000000000000
[ 187.346802][ T8043] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 187.347288][ T8043] CR2: 00007fff92c60000 CR3: 0000000124c28000 CR4: 00000000003506f0
[ 187.347888][ T8043] Kernel panic - not syncing: Fatal exception
[ 187.348594][ T8043] Kernel Offset: disabled
[ 187.348906][ T8043] Rebooting in 86400 seconds..
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