| Message ID | 20221101022840.1351163-2-tgsp002@gmail.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [-next,1/2] PM: hibernate: fix spelling mistake for annotation | expand |
在 2022/11/4 00:25, Rafael J. Wysocki 写道: > On Tue, Nov 1, 2022 at 3:28 AM TGSP <tgsp002@gmail.com> wrote: >> >> From: xiongxin <xiongxin@kylinos.cn> >> >> 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 <xiongxin@kylinos.cn> >> --- >> 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 >>
On Fri, Nov 4, 2022 at 8:31 AM TGSP <tgsp002@gmail.com> wrote: > > 在 2022/11/4 00:25, Rafael J. Wysocki 写道: > > On Tue, Nov 1, 2022 at 3:28 AM TGSP <tgsp002@gmail.com> wrote: > >> > >> From: xiongxin <xiongxin@kylinos.cn> > >> > >> 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? No, you aren't. The formula is fine. I've attempted to explain it to you, but perhaps it's not been clear enough, sorry about that.
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. *