| Message ID | 20221024190603.3987969-8-shr@devkernel.io (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/block: add bdi sysfs knobs | expand |
On Mon, 24 Oct 2022 12:05:56 -0700 Stefan Roesch <shr@devkernel.io> wrote: > This introduces the bdi_set_max_bytes() function. The max_bytes function > does not store the max_bytes value. Instead it converts the max_bytes > value into the corresponding ratio value. > > ... > > +EXPORT_SYMBOL_GPL(bdi_set_max_bytes); Is this needed?
On Mon, 24 Oct 2022 12:05:56 -0700 Stefan Roesch <shr@devkernel.io> wrote: > This introduces the bdi_set_max_bytes() function. The max_bytes function > does not store the max_bytes value. Instead it converts the max_bytes > value into the corresponding ratio value. > > ... > > --- a/include/linux/backing-dev.h > +++ b/include/linux/backing-dev.h > @@ -108,6 +108,7 @@ static inline unsigned long wb_stat_error(void) > unsigned long long bdi_get_max_bytes(struct backing_dev_info *bdi); > int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio); > int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio); > +int bdi_set_max_bytes(struct backing_dev_info *bdi, unsigned long long max_bytes); > int bdi_set_strict_limit(struct backing_dev_info *bdi, unsigned int strict_limit); > > /* > diff --git a/mm/page-writeback.c b/mm/page-writeback.c > index 8b8936603783..21d7c1880ea8 100644 > --- a/mm/page-writeback.c > +++ b/mm/page-writeback.c > @@ -13,6 +13,7 @@ > */ > > #include <linux/kernel.h> > +#include <linux/math64.h> > #include <linux/export.h> > #include <linux/spinlock.h> > #include <linux/fs.h> > @@ -650,6 +651,28 @@ void wb_domain_exit(struct wb_domain *dom) > */ > static unsigned int bdi_min_ratio; > > +static int bdi_check_pages_limit(unsigned long pages) > +{ > + unsigned long max_dirty_pages = global_dirtyable_memory(); > + > + if (pages > max_dirty_pages / 2) > + return -EINVAL; > + > + return 0; > +} Some code comments are needed here. Explain what it does and why it does it. The "/ 2" seems utterly arbitray - explain why this value was chosen? Why is it better than "/ 3"? > +static unsigned long bdi_ratio_from_pages(unsigned long pages) > +{ > + unsigned long background_thresh; > + unsigned long dirty_thresh; > + unsigned long ratio; > + > + global_dirty_limits(&background_thresh, &dirty_thresh); > + ratio = div64_u64(pages * 100ULL * BDI_RATIO_SCALE, dirty_thresh); `unsigned long' is 32-bit on 32-bit machines, which makes this code a bit odd. Should everything here be u64?
Andrew Morton <akpm@linux-foundation.org> writes: > On Mon, 24 Oct 2022 12:05:56 -0700 Stefan Roesch <shr@devkernel.io> wrote: > >> This introduces the bdi_set_max_bytes() function. The max_bytes function >> does not store the max_bytes value. Instead it converts the max_bytes >> value into the corresponding ratio value. >> >> ... >> >> +EXPORT_SYMBOL_GPL(bdi_set_max_bytes); > > Is this needed? I removed the export in the next version.
Andrew Morton <akpm@linux-foundation.org> writes: > On Mon, 24 Oct 2022 12:05:56 -0700 Stefan Roesch <shr@devkernel.io> wrote: > >> This introduces the bdi_set_max_bytes() function. The max_bytes function >> does not store the max_bytes value. Instead it converts the max_bytes >> value into the corresponding ratio value. >> >> ... >> >> --- a/include/linux/backing-dev.h >> +++ b/include/linux/backing-dev.h >> @@ -108,6 +108,7 @@ static inline unsigned long wb_stat_error(void) >> unsigned long long bdi_get_max_bytes(struct backing_dev_info *bdi); >> int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio); >> int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio); >> +int bdi_set_max_bytes(struct backing_dev_info *bdi, unsigned long long max_bytes); >> int bdi_set_strict_limit(struct backing_dev_info *bdi, unsigned int strict_limit); >> >> /* >> diff --git a/mm/page-writeback.c b/mm/page-writeback.c >> index 8b8936603783..21d7c1880ea8 100644 >> --- a/mm/page-writeback.c >> +++ b/mm/page-writeback.c >> @@ -13,6 +13,7 @@ >> */ >> >> #include <linux/kernel.h> >> +#include <linux/math64.h> >> #include <linux/export.h> >> #include <linux/spinlock.h> >> #include <linux/fs.h> >> @@ -650,6 +651,28 @@ void wb_domain_exit(struct wb_domain *dom) >> */ >> static unsigned int bdi_min_ratio; >> >> +static int bdi_check_pages_limit(unsigned long pages) >> +{ >> + unsigned long max_dirty_pages = global_dirtyable_memory(); >> + >> + if (pages > max_dirty_pages / 2) >> + return -EINVAL; >> + >> + return 0; >> +} > > Some code comments are needed here. Explain what it does and why it > does it. The "/ 2" seems utterly arbitray - explain why this value was > chosen? Why is it better than "/ 3"? > > I changed the check to (pages > max_dirty_pages) > >> +static unsigned long bdi_ratio_from_pages(unsigned long pages) >> +{ >> + unsigned long background_thresh; >> + unsigned long dirty_thresh; >> + unsigned long ratio; >> + >> + global_dirty_limits(&background_thresh, &dirty_thresh); >> + ratio = div64_u64(pages * 100ULL * BDI_RATIO_SCALE, dirty_thresh); > > `unsigned long' is 32-bit on 32-bit machines, which makes this code a > bit odd. Should everything here be u64? The function global_dirty_limits() uses unsigned long pointers for its arguments. unsigned long looks like a better fit. Any thoughts?
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h index cb0e66564d4d..5eb1ae3410b2 100644 --- a/include/linux/backing-dev.h +++ b/include/linux/backing-dev.h @@ -108,6 +108,7 @@ static inline unsigned long wb_stat_error(void) unsigned long long bdi_get_max_bytes(struct backing_dev_info *bdi); int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio); int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio); +int bdi_set_max_bytes(struct backing_dev_info *bdi, unsigned long long max_bytes); int bdi_set_strict_limit(struct backing_dev_info *bdi, unsigned int strict_limit); /* diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 8b8936603783..21d7c1880ea8 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -13,6 +13,7 @@ */ #include <linux/kernel.h> +#include <linux/math64.h> #include <linux/export.h> #include <linux/spinlock.h> #include <linux/fs.h> @@ -650,6 +651,28 @@ void wb_domain_exit(struct wb_domain *dom) */ static unsigned int bdi_min_ratio; +static int bdi_check_pages_limit(unsigned long pages) +{ + unsigned long max_dirty_pages = global_dirtyable_memory(); + + if (pages > max_dirty_pages / 2) + return -EINVAL; + + return 0; +} + +static unsigned long bdi_ratio_from_pages(unsigned long pages) +{ + unsigned long background_thresh; + unsigned long dirty_thresh; + unsigned long ratio; + + global_dirty_limits(&background_thresh, &dirty_thresh); + ratio = div64_u64(pages * 100ULL * BDI_RATIO_SCALE, dirty_thresh); + + return ratio; +} + static unsigned long long bdi_get_bytes(unsigned int ratio) { unsigned long background_thresh; @@ -723,6 +746,21 @@ unsigned long long bdi_get_max_bytes(struct backing_dev_info *bdi) } EXPORT_SYMBOL_GPL(bdi_get_max_bytes); +int bdi_set_max_bytes(struct backing_dev_info *bdi, unsigned long long max_bytes) +{ + int ret; + unsigned long pages = max_bytes >> PAGE_SHIFT; + unsigned long max_ratio; + + ret = bdi_check_pages_limit(pages); + if (ret) + return ret; + + max_ratio = bdi_ratio_from_pages(pages); + return __bdi_set_max_ratio(bdi, max_ratio); +} +EXPORT_SYMBOL_GPL(bdi_set_max_bytes); + int bdi_set_strict_limit(struct backing_dev_info *bdi, unsigned int strict_limit) { if (strict_limit > 1)
This introduces the bdi_set_max_bytes() function. The max_bytes function does not store the max_bytes value. Instead it converts the max_bytes value into the corresponding ratio value. Signed-off-by: Stefan Roesch <shr@devkernel.io> --- include/linux/backing-dev.h | 1 + mm/page-writeback.c | 38 +++++++++++++++++++++++++++++++++++++ 2 files changed, 39 insertions(+)