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mm: add bdi_get_max_bytes() function

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This adds a function to return the specified value for max_bytes. It
converts the stored max_ratio of the bdi to the corresponding bytes
value. It introduces the bdi_get_bytes helper function to do the
conversion. This is an approximation as it is based on the value that is
returned by global_dirty_limits(), which can change. The helper function
will also be used by the min_bytes bdi knob.

Link: https://lkml.kernel.org/r/20221119005215.3052436-6-shr@devkernel.io
Signed-off-by: Stefan Roesch <shr@devkernel.io>
Cc: Chris Mason <clm@meta.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Stefan Roesch 2022-11-18 16:52:00 -08:00 committed by Andrew Morton
parent ae82291e9c
commit 00df7d5126
2 changed files with 18 additions and 0 deletions
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1
include/linux/backing-dev.h
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@ -105,6 +105,7 @@ static inline unsigned long wb_stat_error(void)
/* BDI ratio is expressed as part per 1000000 for finer granularity. */
#define BDI_RATIO_SCALE 10000
u64 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_strict_limit(struct backing_dev_info *bdi, unsigned int strict_limit);

17
mm/page-writeback.c
View File

@ -650,6 +650,18 @@ void wb_domain_exit(struct wb_domain *dom)
*/
static unsigned int bdi_min_ratio;
static u64 bdi_get_bytes(unsigned int ratio)
{
unsigned long background_thresh;
unsigned long dirty_thresh;
u64 bytes;
global_dirty_limits(&background_thresh, &dirty_thresh);
bytes = (dirty_thresh * PAGE_SIZE * ratio) / BDI_RATIO_SCALE / 100;
return bytes;
}
int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio)
{
unsigned int delta;
@ -701,6 +713,11 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned max_ratio)
}
EXPORT_SYMBOL(bdi_set_max_ratio);
u64 bdi_get_max_bytes(struct backing_dev_info *bdi)
{
return bdi_get_bytes(bdi->max_ratio);
}
int bdi_set_strict_limit(struct backing_dev_info *bdi, unsigned int strict_limit)
{
if (strict_limit > 1)