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Mon, 3 Nov 2025 16:49:27 +0000 (GMT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=harmstone.com; s=mail; t=1762188567; bh=Pe/DV0A17vmtgKXNI1x+5tjznCB5XqGuhee9GH4vKRM=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=mFVkXXAZKl9R5bvoAWRMH64za366h7L5TEYnIA6z7H6SU1s5VaSeCmiZbwRln0wzX yeApOmz4ZazXkhPz4JijfaNDsZAkR7NIYORXuPxzPHqe5vMj7D8amrVHB13YR0K3G9 vS41Yun3Lgzu3Ycn7rQMrcKiA4wfn0TlttUE2FJI= Message-ID: <475df362-2bf8-4cfd-b85d-df4579ddc8d3@harmstone.com> Date: Mon, 3 Nov 2025 16:49:26 +0000 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Subject: Re: [PATCH v4 15/16] btrfs: handle discarding fully-remapped block groups To: Boris Burkov , kernel test robot Cc: linux-btrfs@vger.kernel.org, oe-kbuild-all@lists.linux.dev References: <20251024181227.32228-16-mark@harmstone.com> <202510272322.N1S5rdDc-lkp@intel.com> Content-Language: en-US From: Mark Harmstone Autocrypt: addr=mark@harmstone.com; keydata= xsBNBFp/GMsBCACtFsuHZqHWpHtHuFkNZhMpiZMChyou4X8Ueur3XyF8KM2j6TKkZ5M/72qT EycEM0iU1TYVN/Rb39gBGtRclLFVY1bx4i+aUCzh/4naRxqHgzM2SeeLWHD0qva0gIwjvoRs FP333bWrFKPh5xUmmSXBtBCVqrW+LYX4404tDKUf5wUQ9bQd2ItFRM2mU/l6TUHVY2iMql6I s94Bz5/Zh4BVvs64CbgdyYyQuI4r2tk/Z9Z8M4IjEzQsjSOfArEmb4nj27R3GOauZTO2aKlM 8821rvBjcsMk6iE/NV4SPsfCZ1jvL2UC3CnWYshsGGnfd8m2v0aLFSHZlNd+vedQOTgnABEB AAHNI01hcmsgSGFybXN0b25lIDxtYXJrQGhhcm1zdG9uZS5jb20+wsCRBBMBCAA7AhsvBQsJ CAcCBhUICQoLAgQWAgMBAh4BAheAFiEEG2JgKYgV0WRwIJAqbKyhHeAWK+0FAmRQOkICGQEA CgkQbKyhHeAWK+22wgf/dBOJ0pHdkDi5fNmWynlxteBsy3VCo0qC25DQzGItL1vEY95EV4uX re3+6eVRBy9gCKHBdFWk/rtLWKceWVZ86XfTMHgy+ZnIUkrD3XZa3oIV6+bzHgQ15rXXckiE A5N+6JeY/7hAQpSh/nOqqkNMmRkHAZ1ZA/8KzQITe1AEULOn+DphERBFD5S/EURvC8jJ5hEr lQj8Tt5BvA57sLNBmQCE19+IGFmq36EWRCRJuH0RU05p/MXPTZB78UN/oGT69UAIJAEzUzVe sN3jiXuUWBDvZz701dubdq3dEdwyrCiP+dmlvQcxVQqbGnqrVARsGCyhueRLnN7SCY1s5OHK ls7ATQRafxjLAQgAvkcSlqYuzsqLwPzuzoMzIiAwfvEW3AnZxmZn9bQ+ashB9WnkAy2FZCiI /BPwiiUjqgloaVS2dIrVFAYbynqSbjqhki+uwMliz7/jEporTDmxx7VGzdbcKSCe6rkE/72o 6t7KG0r55cmWnkdOWQ965aRnRAFY7Zzd+WLqlzeoseYsNj36RMaqNR7aL7x+kDWnwbw+jgiX tgNBcnKtqmJc04z/sQTa+sUX53syht1Iv4wkATN1W+ZvQySxHNXK1r4NkcDA9ZyFA3NeeIE6 ejiO7RyC0llKXk78t0VQPdGS6HspVhYGJJt21c5vwSzIeZaneKULaxXGwzgYFTroHD9n+QAR AQABwsGsBBgBCAAgFiEEG2JgKYgV0WRwIJAqbKyhHeAWK+0FAlp/GMsCGy4BQAkQbKyhHeAW K+3AdCAEGQEIAB0WIQR6bEAu0hwk2Q9ibSlt5UHXRQtUiwUCWn8YywAKCRBt5UHXRQtUiwdE B/9OpyjmrshY40kwpmPwUfode2Azufd3QRdthnNPAY8Tv9erwsMS3sMh+M9EP+iYJh+AIRO7 fDN/u0AWIqZhHFzCndqZp8JRYULnspXSKPmVSVRIagylKew406XcAVFpEjloUtDhziBN7ykk srAMoLASaBHZpAfp8UAGDrr8Fx1on46rDxsWbh1K1h4LEmkkVooDELjsbN9jvxr8ym8Bkt54 FcpypTOd8jkt/lJRvnKXoL3rZ83HFiUFtp/ZkveZKi53ANUaqy5/U5v0Q0Ppz9ujcRA9I/V3 B66DKMg1UjiigJG6espeIPjXjw0n9BCa9jqGICyJTIZhnbEs1yEpsM87eUIH/0UFLv0b8IZe pL/3QfiFoYSqMEAwCVDFkCt4uUVFZczKTDXTFkwm7zflvRHdy5QyVFDWMyGnTN+Bq48Gwn1M uRT/Sg37LIjAUmKRJPDkVr/DQDbyL6rTvNbA3hTBu392v0CXFsvpgRNYaT8oz7DDBUUWj2Ny 6bZCBtwr/O+CwVVqWRzKDQgVo4t1xk2ts1F0R1uHHLsX7mIgfXBYdo/y4UgFBAJH5NYUcBR+ QQcOgUUZeF2MC9i0oUaHJOIuuN2q+m9eMpnJdxVKAUQcZxDDvNjZwZh+ejsgG4Ejd2XR/T0y XFoR/dLFIhf2zxRylN1xq27M9P2t1xfQFocuYToPsVk= In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 31/10/2025 10.12 pm, Boris Burkov wrote: > On Tue, Oct 28, 2025 at 12:04:11AM +0800, kernel test robot wrote: >> Hi Mark, >> >> kernel test robot noticed the following build warnings: >> >> [auto build test WARNING on kdave/for-next] >> [also build test WARNING on next-20251027] >> [cannot apply to linus/master v6.18-rc3] >> [If your patch is applied to the wrong git tree, kindly drop us a note. >> And when submitting patch, we suggest to use '--base' as documented in >> https://git-scm.com/docs/git-format-patch#_base_tree_information] >> >> url: https://github.com/intel-lab-lkp/linux/commits/Mark-Harmstone/btrfs-add-definitions-and-constants-for-remap-tree/20251025-021910 >> base: https://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux.git for-next >> patch link: https://lore.kernel.org/r/20251024181227.32228-16-mark%40harmstone.com >> patch subject: [PATCH v4 15/16] btrfs: handle discarding fully-remapped block groups >> config: arm-randconfig-003-20251027 (https://download.01.org/0day-ci/archive/20251027/202510272322.N1S5rdDc-lkp@intel.com/config) >> compiler: arm-linux-gnueabi-gcc (GCC) 8.5.0 >> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251027/202510272322.N1S5rdDc-lkp@intel.com/reproduce) >> >> If you fix the issue in a separate patch/commit (i.e. not just a new version of >> the same patch/commit), kindly add following tags >> | Reported-by: kernel test robot >> | Closes: https://lore.kernel.org/oe-kbuild-all/202510272322.N1S5rdDc-lkp@intel.com/ >> >> Note: it may well be a FALSE warning. FWIW you are at least aware of it now. >> http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings >> >> All warnings (new ones prefixed by >>): >> >> fs/btrfs/discard.c: In function 'btrfs_discard_workfn': >>>> fs/btrfs/discard.c:596:6: warning: 'discard_state' may be used uninitialized in this function [-Wmaybe-uninitialized] >> if (discard_state == BTRFS_DISCARD_BITMAPS || >> ^ > > I think this gets set by peek_discard_list() so I don't think this is > a valid warning. You are correct. discard_state gets initialized if the return value of peek_discard_list() is not NULL, and if it is NULL we return before we use it. This is an ancient version of GCC, the warning doesn't trigger on GCC 15 - presumably it has better control flow analysis. I don't think the robot should be compiling with this warning turned on for old compiler versions, if it's prone to false positives. >> >> >> vim +/discard_state +596 fs/btrfs/discard.c >> >> 513 >> 514 /* >> 515 * Discard work queue callback >> 516 * >> 517 * @work: work >> 518 * >> 519 * Find the next block_group to start discarding and then discard a single >> 520 * region. It does this in a two-pass fashion: first extents and second >> 521 * bitmaps. Completely discarded block groups are sent to the unused_bgs path. >> 522 */ >> 523 static void btrfs_discard_workfn(struct work_struct *work) >> 524 { >> 525 struct btrfs_discard_ctl *discard_ctl; >> 526 struct btrfs_block_group *block_group; >> 527 enum btrfs_discard_state discard_state; >> 528 int discard_index = 0; >> 529 u64 trimmed = 0; >> 530 u64 minlen = 0; >> 531 u64 now = ktime_get_ns(); >> 532 >> 533 discard_ctl = container_of(work, struct btrfs_discard_ctl, work.work); >> 534 >> 535 block_group = peek_discard_list(discard_ctl, &discard_state, >> 536 &discard_index, now); >> 537 if (!block_group) >> 538 return; >> 539 if (!btrfs_run_discard_work(discard_ctl)) { >> 540 spin_lock(&discard_ctl->lock); >> 541 btrfs_put_block_group(block_group); >> 542 discard_ctl->block_group = NULL; >> 543 spin_unlock(&discard_ctl->lock); >> 544 return; >> 545 } >> 546 if (now < block_group->discard_eligible_time) { >> 547 spin_lock(&discard_ctl->lock); >> 548 btrfs_put_block_group(block_group); >> 549 discard_ctl->block_group = NULL; >> 550 spin_unlock(&discard_ctl->lock); >> 551 btrfs_discard_schedule_work(discard_ctl, false); >> 552 return; >> 553 } >> 554 >> 555 /* Perform discarding */ >> 556 minlen = discard_minlen[discard_index]; >> 557 >> 558 switch (discard_state) { >> 559 case BTRFS_DISCARD_BITMAPS: { >> 560 u64 maxlen = 0; >> 561 >> 562 /* >> 563 * Use the previous levels minimum discard length as the max >> 564 * length filter. In the case something is added to make a >> 565 * region go beyond the max filter, the entire bitmap is set >> 566 * back to BTRFS_TRIM_STATE_UNTRIMMED. >> 567 */ >> 568 if (discard_index != BTRFS_DISCARD_INDEX_UNUSED) >> 569 maxlen = discard_minlen[discard_index - 1]; >> 570 >> 571 btrfs_trim_block_group_bitmaps(block_group, &trimmed, >> 572 block_group->discard_cursor, >> 573 btrfs_block_group_end(block_group), >> 574 minlen, maxlen, true); >> 575 discard_ctl->discard_bitmap_bytes += trimmed; >> 576 >> 577 break; >> 578 } >> 579 >> 580 case BTRFS_DISCARD_FULLY_REMAPPED: >> 581 btrfs_trim_fully_remapped_block_group(block_group); >> 582 break; >> 583 >> 584 default: >> 585 btrfs_trim_block_group_extents(block_group, &trimmed, >> 586 block_group->discard_cursor, >> 587 btrfs_block_group_end(block_group), >> 588 minlen, true); >> 589 discard_ctl->discard_extent_bytes += trimmed; >> 590 >> 591 break; >> 592 } >> 593 >> 594 /* Determine next steps for a block_group */ >> 595 if (block_group->discard_cursor >= btrfs_block_group_end(block_group)) { >> > 596 if (discard_state == BTRFS_DISCARD_BITMAPS || >> 597 discard_state == BTRFS_DISCARD_FULLY_REMAPPED) { >> 598 btrfs_finish_discard_pass(discard_ctl, block_group); >> 599 } else { >> 600 block_group->discard_cursor = block_group->start; >> 601 spin_lock(&discard_ctl->lock); >> 602 if (block_group->discard_state != >> 603 BTRFS_DISCARD_RESET_CURSOR) >> 604 block_group->discard_state = >> 605 BTRFS_DISCARD_BITMAPS; >> 606 spin_unlock(&discard_ctl->lock); >> 607 } >> 608 } >> 609 >> 610 now = ktime_get_ns(); >> 611 spin_lock(&discard_ctl->lock); >> 612 discard_ctl->prev_discard = trimmed; >> 613 discard_ctl->prev_discard_time = now; >> 614 btrfs_put_block_group(block_group); >> 615 discard_ctl->block_group = NULL; >> 616 __btrfs_discard_schedule_work(discard_ctl, now, false); >> 617 spin_unlock(&discard_ctl->lock); >> 618 } >> 619 >> >> -- >> 0-DAY CI Kernel Test Service >> https://github.com/intel/lkp-tests/wiki