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[109.116.17.225]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-378e73f9999sm6870236f8f.58.2024.09.16.03.51.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 16 Sep 2024 03:51:15 -0700 (PDT) Message-ID: Date: Mon, 16 Sep 2024 12:51:14 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 2/3] btrfs: Split remaining space to discard in chunks To: Qu Wenruo Cc: Chris Mason , Josef Bacik , David Sterba , linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org References: <20240916101615.116164-1-luca.stefani.ge1@gmail.com> <20240916101615.116164-3-luca.stefani.ge1@gmail.com> <98991e9d-cce0-48ad-b77c-b7d3eff71dca@suse.com> Content-Language: en-US From: Luca Stefani In-Reply-To: <98991e9d-cce0-48ad-b77c-b7d3eff71dca@suse.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 16/09/24 12:39, Qu Wenruo wrote: > > > 在 2024/9/16 19:46, Luca Stefani 写道: >> Per Qu Wenruo in case we have a very large disk, e.g. 8TiB device, >> mostly empty although we will do the split according to our super block >> locations, the last super block ends at 256G, we can submit a huge >> discard for the range [256G, 8T), causing a super large delay. >> >> We now split the space left to discard based on BTRFS_MAX_DATA_CHUNK_SIZE >> in preparation of introduction of cancellation signals handling. >> >> Link: https://bugzilla.kernel.org/show_bug.cgi?id=219180 >> Link: https://bugzilla.suse.com/show_bug.cgi?id=1229737 >> Signed-off-by: Luca Stefani >> --- >>   fs/btrfs/extent-tree.c | 24 +++++++++++++++++++----- >>   1 file changed, 19 insertions(+), 5 deletions(-) >> >> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c >> index a5966324607d..cbe66d0acff8 100644 >> --- a/fs/btrfs/extent-tree.c >> +++ b/fs/btrfs/extent-tree.c >> @@ -1239,7 +1239,7 @@ static int btrfs_issue_discard(struct >> block_device *bdev, u64 start, u64 len, >>                      u64 *discarded_bytes) >>   { >>       int j, ret = 0; >> -    u64 bytes_left, end; >> +    u64 bytes_left, bytes_to_discard, end; >>       u64 aligned_start = ALIGN(start, 1 << SECTOR_SHIFT); >>       /* Adjust the range to be aligned to 512B sectors if necessary. */ >> @@ -1300,13 +1300,27 @@ static int btrfs_issue_discard(struct >> block_device *bdev, u64 start, u64 len, >>           bytes_left = end - start; >>       } >> -    if (bytes_left) { >> +    while (bytes_left) { >> +        if (bytes_left > BTRFS_MAX_DATA_CHUNK_SIZE) >> +            bytes_to_discard = BTRFS_MAX_DATA_CHUNK_SIZE; > > That MAX_DATA_CHUNK_SIZE is only possible for RAID0/RAID10/RAID5/RAID6, > by spanning the device extents across multiple devices. > > For each device, the maximum size is limited to 1G (check > init_alloc_chunk_ctl_policy_regular()). > > So you can just limit it to 1G instead. > (If you want, you can also extract that into a macro as a cleanup). I think SZ_1G is enough for now. > > Furthermore, you can use min() instead of a if (). > > So you only need: > >         bytes_to_discard = min(SZ_1G, bytes_left); > > Otherwise this looks good enough to me. > If the 1G size is not good enough, we can later tune it to smaller values. > > Personally speaking I think 1G would be enough. > > Thanks, > Qu Ack, done in v5 >> +        else >> +            bytes_to_discard = bytes_left; >> + >>           ret = blkdev_issue_discard(bdev, start >> SECTOR_SHIFT, >> -                       bytes_left >> SECTOR_SHIFT, >> +                       bytes_to_discard >> SECTOR_SHIFT, >>                          GFP_NOFS); >> -        if (!ret) >> -            *discarded_bytes += bytes_left; >> + >> +        if (ret) { >> +            if (ret != -EOPNOTSUPP) >> +                break; >> +            continue; >> +        } >> + >> +        start += bytes_to_discard; >> +        bytes_left -= bytes_to_discard; >> +        *discarded_bytes += bytes_to_discard; >>       } >> + >>       return ret; >>   }