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[2403:580d:fda1::c8a]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-22fc82bfad1sm96637365ad.250.2025.05.14.03.38.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 14 May 2025 03:38:29 -0700 (PDT) Message-ID: Date: Wed, 14 May 2025 20:08:20 +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 1/3] btrfs: fix wrong start offset for delalloc space release during mmap write To: fdmanana@kernel.org, linux-btrfs@vger.kernel.org References: <79efbad28a262a6dbe07decd0f49b5a91a167c15.1747217722.git.fdmanana@suse.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: <79efbad28a262a6dbe07decd0f49b5a91a167c15.1747217722.git.fdmanana@suse.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2025/5/14 19:59, fdmanana@kernel.org 写道: > From: Filipe Manana > > If we're doing a mmap write against a folio that has i_size somewhere in > the middle and we have multiple sectors in the folio, we may have to > release excess space previously reserved, for the range going from the > rounded up (to sector size) i_size to the folio's end offset. We are > calculating the right amount to release and passing it to > btrfs_delalloc_release_space(), but we are passing the wrong start offset > of that range - we're passing the folio's start offset instead of the > end offset, plus 1, of the range for which we keep the reservation. This > may result in releasing more space then we should and eventually trigger > an underflow of the data space_info's bytes_may_use counter. > > So fix this by passing the start offset as 'end + 1' instead of > 'page_start' to btrfs_delalloc_release_space(). > > Fixes: d0b7da88f640 ("Btrfs: btrfs_page_mkwrite: Reserve space in sectorsized units") > Signed-off-by: Filipe Manana Reviewed-by: Qu Wenruo Just curious how did you spot this, by pure eyeballing or you have some tool exposing this? Thanks, Qu> --- > fs/btrfs/file.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c > index 660a73b6af90..32aad1b02b01 100644 > --- a/fs/btrfs/file.c > +++ b/fs/btrfs/file.c > @@ -1918,7 +1918,7 @@ static vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf) > if (reserved_space < fsize) { > end = page_start + reserved_space - 1; > btrfs_delalloc_release_space(BTRFS_I(inode), > - data_reserved, page_start, > + data_reserved, end + 1, > fsize - reserved_space, true); > } > }