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Mon, 14 Sep 2026 03:21:25 -0700 (PDT) Received: from [172.16.0.229] ([159.196.52.54]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39d9959ac65sm19856927a91.16.2026.09.14.03.21.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 14 Sep 2026 03:21:24 -0700 (PDT) Message-ID: <3f3209ea-44bf-4dc4-9567-d936703435d2@suse.com> Date: Mon, 14 Sep 2026 19:51:16 +0930 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1] btrfs: discard: fix warning for discard_state To: Jiahao Li , dsterba@suse.com, mason@kernel.org Cc: linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, Jiahao Li References: <20260914092222.1465563-1-lijiahao202609@163.com> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=wqu@suse.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNGFF1IFdlbnJ1byA8d3F1QHN1c2UuY29tPsLAlAQTAQgAPgIbAwULCQgHAgYVCAkKCwIE FgIDAQIeAQIXgBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXVgBQkQ/lqxAAoJEMI9kfOh Jf6o+jIH/2KhFmyOw4XWAYbnnijuYqb/obGae8HhcJO2KIGcxbsinK+KQFTSZnkFxnbsQ+VY fvtWBHGt8WfHcNmfjdejmy9si2jyy8smQV2jiB60a8iqQXGmsrkuR+AM2V360oEbMF3gVvim 2VSX2IiW9KERuhifjseNV1HLk0SHw5NnXiWh1THTqtvFFY+CwnLN2GqiMaSLF6gATW05/sEd V17MdI1z4+WSk7D57FlLjp50F3ow2WJtXwG8yG8d6S40dytZpH9iFuk12Sbg7lrtQxPPOIEU rpmZLfCNJJoZj603613w/M8EiZw6MohzikTWcFc55RLYJPBWQ+9puZtx1DopW2jOwE0EWdWB rwEIAKpT62HgSzL9zwGe+WIUCMB+nOEjXAfvoUPUwk+YCEDcOdfkkM5FyBoJs8TCEuPXGXBO Cl5P5B8OYYnkHkGWutAVlUTV8KESOIm/KJIA7jJA+Ss9VhMjtePfgWexw+P8itFRSRrrwyUf E+0WcAevblUi45LjWWZgpg3A80tHP0iToOZ5MbdYk7YFBE29cDSleskfV80ZKxFv6koQocq0 vXzTfHvXNDELAuH7Ms/WJcdUzmPyBf3Oq6mKBBH8J6XZc9LjjNZwNbyvsHSrV5bgmu/THX2n g/3be+iqf6OggCiy3I1NSMJ5KtR0q2H2Nx2Vqb1fYPOID8McMV9Ll6rh8S8AEQEAAcLAfAQY AQgAJgIbDBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXWBBQkQ/lrSAAoJEMI9kfOhJf6o cakH+QHwDszsoYvmrNq36MFGgvAHRjdlrHRBa4A1V1kzd4kOUokongcrOOgHY9yfglcvZqlJ qfa4l+1oxs1BvCi29psteQTtw+memmcGruKi+YHD7793zNCMtAtYidDmQ2pWaLfqSaryjlzR /3tBWMyvIeWZKURnZbBzWRREB7iWxEbZ014B3gICqZPDRwwitHpH8Om3eZr7ygZck6bBa4MU o1XgbZcspyCGqu1xF/bMAY2iCDcq6ULKQceuKkbeQ8qxvt9hVxJC2W3lHq8dlK1pkHPDg9wO JoAXek8MF37R8gpLoGWl41FIUb3hFiu3zhDDvslYM4BmzI18QgQTQnotJH8= In-Reply-To: <20260914092222.1465563-1-lijiahao202609@163.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2026/9/14 18:52, Jiahao Li 写道: > From: Jiahao Li > > Building with -Werror=mabe-uninitialized fails: > fs/btrfs/discard.c:553:9: error: 'discard_state' may be used > uninitialized [-Werror=maybe-uninitialized] > > The compiler cannot prove that discard_state is assigned on every path > before it is read. Compiler and its version, a lot of times such false alerts are just compiler version dependent. In my case, gcc 16.2.1 failed to reproduced this false alert. Initialize it to BTRFS_DISCARD_EXTENTS, which is the > state the variable holds when the loop is first entered, this does not > change runtime behavior, so the warning is gone and the value is always > well defined. It's a false alert. Firstly if peek_discard_list() didn't find a bg, btrfs_discard_workfn() returned immediately. Secondly if a bg is found in peek_discard_list(), *discard_state is fetched from bg's discard_state. So all paths should be fine. > > Signed-off-by: Jiahao Li > --- > fs/btrfs/discard.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/btrfs/discard.c b/fs/btrfs/discard.c > index 1c304bf473e5..413a804ff46b 100644 > --- a/fs/btrfs/discard.c > +++ b/fs/btrfs/discard.c > @@ -519,7 +519,7 @@ static void btrfs_discard_workfn(struct work_struct *work) > { > struct btrfs_discard_ctl *discard_ctl; > struct btrfs_block_group *block_group; > - enum btrfs_discard_state discard_state; > + enum btrfs_discard_state discard_state = BTRFS_DISCARD_EXTENTS; > int discard_index = 0; > u64 trimmed = 0; > u64 minlen = 0;