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b=WN9hjwlmx0HVdb4YF1Sq3oj3HwrhyUQI+IDlCYmRb6l10BP2p8TewhHz/yW/36pmr q1/+2NLql1wgw6femargLL/rf4Q+ZiKFQC9JHm7DRpbiebO1GchSNvBXANY6xS4Xcp 9pk/lwCQz4Mwf+ffx6xWmRasxaX/8e3Hmgpget+YSCPC6tcrSxl7sRX89k0Auvyu+M UjXFuZObfnoXGKmfMfoylih5IGFJ88Av7h63oRo7WZFt7HQ2yUibuGVOgPt78uLJMv 2jrMIMwVZlInZKczqxYqEnpP4ku47CZtPvfV1JtVba21KdzM59gA8ZzTzYgV1tLPf8 Aci6vSRMIfV5w== Date: Wed, 18 Dec 2024 18:27:36 -0800 From: Luis Chamberlain To: Matthew Wilcox Cc: hare@suse.de, dave@stgolabs.net, david@fromorbit.com, djwong@kernel.org, kbusch@kernel.org, john.g.garry@oracle.com, hch@lst.de, ritesh.list@gmail.com, linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, linux-block@vger.kernel.org, gost.dev@samsung.com, p.raghav@samsung.com, da.gomez@samsung.com, kernel@pankajraghav.com Subject: Re: [PATCH 0/5] fs/buffer: strack reduction on async read Message-ID: References: <20241218022626.3668119-1-mcgrof@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam05 X-Stat-Signature: 8w11ezk7nkx1gq8gik7dmhis9499yfgb X-Rspamd-Queue-Id: 1C5021C0017 X-Rspam-User: X-HE-Tag: 1734575196-78173 X-HE-Meta: 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 n6esfrhR v3SoLriyH1/QI7LFrnoHgZs1AdjYYoyjHjRRTUptGezXSEvTgpRTh5wcPU8/84utRmWWbKJlrFAS4p1qBedHFY56oOfPcHfViC2p2AeUm5sXwJb595mjK8ZPVTkZYQk2dbiqH8hInbyHdLzCuklAuas2t7T1ek6we2K83tGk9/Gj9HwNFgqL+MFV9hFprwxLSJUML8/q1cBFgfhLtLSaKe6OIxcEkS+rtdTuRKm9qu3WmXzE42c2kSCUntyJPMI1NTeb3R2+s4RFWG7fSt+AIGuUEUxg839/mAP9F X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Dec 18, 2024 at 08:05:29PM +0000, Matthew Wilcox wrote: > On Tue, Dec 17, 2024 at 06:26:21PM -0800, Luis Chamberlain wrote: > > This splits up a minor enhancement from the bs > ps device support > > series into its own series for better review / focus / testing. > > This series just addresses the reducing the array size used and cleaning > > up the async read to be easier to read and maintain. > > How about this approach instead -- get rid of the batch entirely? Less is more! I wish it worked, but we end up with a null pointer on ext4/032 (and indeed this is the test that helped me find most bugs in what I was working on): [ 105.942462] loop0: detected capacity change from 0 to 1342177280 [ 106.034851] BUG: kernel NULL pointer dereference, address: 0000000000000000 [ 106.036903] #PF: supervisor read access in kernel mode [ 106.038366] #PF: error_code(0x0000) - not-present page [ 106.039819] PGD 0 P4D 0 [ 106.040574] Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI [ 106.041967] CPU: 2 UID: 0 PID: 29 Comm: ksoftirqd/2 Not tainted 6.13.0-rc3+ #42 [ 106.044018] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 2024.08-1 09/18/2024 [ 106.046300] RIP: 0010:end_buffer_async_read_io+0x11/0x90 [ 106.047819] Code: f2 ff 0f 1f 80 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 0f 1f 44 00 00 53 48 8b 47 10 48 89 fb 48 8b 40 18 <48> 8b 00 f6 40 0d 40 74 0d 0f b7 00 66 25 00 f0 66 3d 00 80 74 09 [ 106.053016] RSP: 0018:ffffa85880137dd0 EFLAGS: 00010246 [ 106.054499] RAX: 0000000000000000 RBX: ffff95e38f22e5b0 RCX: ffff95e39c8753e0 [ 106.056507] RDX: ffff95e3809f8000 RSI: 0000000000000001 RDI: ffff95e38f22e5b0 [ 106.058530] RBP: 0000000000000400 R08: ffff95e3a326b040 R09: 0000000000000001 [ 106.060546] R10: ffffffffbb6070c0 R11: 00000000002dc6c0 R12: 0000000000000000 [ 106.062426] R13: ffff95e3960ea800 R14: ffff95e39586ae40 R15: 0000000000000400 [ 106.064223] FS: 0000000000000000(0000) GS:ffff95e3fbc80000(0000) knlGS:0000000000000000 [ 106.066155] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 106.067473] CR2: 0000000000000000 CR3: 00000001226e2006 CR4: 0000000000772ef0 [ 106.069085] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 106.070571] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 106.072050] PKRU: 55555554 [ 106.072632] Call Trace: [ 106.073176] [ 106.073611] ? __die_body.cold+0x19/0x26 [ 106.074383] ? page_fault_oops+0xa2/0x230 [ 106.075155] ? __smp_call_single_queue+0xa7/0x110 [ 106.076077] ? do_user_addr_fault+0x63/0x640 [ 106.076916] ? exc_page_fault+0x7a/0x190 [ 106.077639] ? asm_exc_page_fault+0x22/0x30 [ 106.078394] ? end_buffer_async_read_io+0x11/0x90 [ 106.079245] end_bio_bh_io_sync+0x23/0x40 [ 106.079973] blk_update_request+0x178/0x420 [ 106.080727] ? finish_task_switch.isra.0+0x94/0x290 [ 106.081600] blk_mq_end_request+0x18/0x30 [ 106.082281] blk_complete_reqs+0x3d/0x50 [ 106.082954] handle_softirqs+0xf9/0x2c0 [ 106.083607] ? __pfx_smpboot_thread_fn+0x10/0x10 [ 106.084393] run_ksoftirqd+0x37/0x50 [ 106.085012] smpboot_thread_fn+0x184/0x220 [ 106.085688] kthread+0xda/0x110 [ 106.086208] ? __pfx_kthread+0x10/0x10 [ 106.086824] ret_from_fork+0x2d/0x50 [ 106.087409] ? __pfx_kthread+0x10/0x10 [ 106.088013] ret_from_fork_asm+0x1a/0x30 [ 106.088658] [ 106.089045] Modules linked in: loop sunrpc 9p nls_iso8859_1 nls_cp437 vfat fat kvm_intel kvm crct10dif_pclmul ghash_clmulni_intel sha512_ssse3 sha512_generic sha256_ssse3 sha1_ssse3 aesni_intel gf128mul crypto_simd cryptd virtio_balloon 9pnet_virtio virtio_console joydev button evdev serio_raw nvme_fabrics nvme_core dm_mod drm nfnetlink vsock_loopback vmw_vsock_virtio_transport_common vsock autofs4 ext4 crc16 mbcache jbd2 btrfs blake2b_generic efivarfs raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c crc32c_generic raid1 raid0 md_mod virtio_net net_failover virtio_blk failover crc32_pclmul crc32c_intel psmouse virtio_pci virtio_pci_legacy_dev virtio_pci_modern_dev virtio virtio_ring [ 106.097895] CR2: 0000000000000000 [ 106.098326] ---[ end trace 0000000000000000 ]--- Luis