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Wysocki" References: <20221101022840.1351163-1-tgsp002@gmail.com> <20221101022840.1351163-2-tgsp002@gmail.com> From: TGSP In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2022/11/4 00:25, Rafael J. Wysocki 写道: > On Tue, Nov 1, 2022 at 3:28 AM TGSP wrote: >> >> From: xiongxin >> >> The actual calculation formula in the code below is: >> >> max_size = (count - (size + PAGES_FOR_IO)) / 2 >> - 2 * DIV_ROUND_UP(reserved_size, PAGE_SIZE); >> >> But function comments are written differently, the comment is wrong? > > It is, and it is more serious than just a spelling mistake. > >> By the way, what exactly do the "/ 2" and "2 *" mean? > > Every page in the image is a copy of an existing allocated page, so > room needs to be made for the two, except for the "IO pages" and > metadata pages that are not copied. Hence, the division by 2. > > Now, the "reserved_size" pages will be allocated right before creating > the image and there will be a copy of each of them in the image, so > there needs to be room for twice as many. According to your interpretation, the formula should be： max_size = (count - 2 * DIV_ROUND_UP(reserved_size, PAGE_SIZE) - (size + PAGES_FOR_IO)) / 2 Am I right? > > I'll adjust the changelog and queue up the path for 6.2. > >> Cc: stable@vger.kernel.org > > I'll add a Fixes tag instead. > >> Signed-off-by: xiongxin >> --- >> kernel/power/snapshot.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c >> index 2a406753af90..c20ca5fb9adc 100644 >> --- a/kernel/power/snapshot.c >> +++ b/kernel/power/snapshot.c >> @@ -1723,8 +1723,8 @@ static unsigned long minimum_image_size(unsigned long saveable) >> * /sys/power/reserved_size, respectively). To make this happen, we compute the >> * total number of available page frames and allocate at least >> * >> - * ([page frames total] + PAGES_FOR_IO + [metadata pages]) / 2 >> - * + 2 * DIV_ROUND_UP(reserved_size, PAGE_SIZE) >> + * ([page frames total] - PAGES_FOR_IO - [metadata pages]) / 2 >> + * - 2 * DIV_ROUND_UP(reserved_size, PAGE_SIZE) >> * >> * of them, which corresponds to the maximum size of a hibernation image. >> * >> -- >> 2.25.1 >>