Commit 1bf27e98 authored by Stefan Roesch's avatar Stefan Roesch Committed by Andrew Morton
Browse files

mm: add bdi_set_max_bytes() function 

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.

Link: https://lkml.kernel.org/r/20221119005215.3052436-8-shr@devkernel.io


Signed-off-by: default avatarStefan Roesch <shr@devkernel.io>
Cc: Chris Mason <clm@meta.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent efc3e6ad

include/linux/backing-dev.h

+1 −0
Original line number Diff line number Diff line
@@ -108,6 +108,7 @@ static inline unsigned long wb_stat_error(void) 
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_max_bytes(struct backing_dev_info *bdi, u64 max_bytes);

int bdi_set_strict_limit(struct backing_dev_info *bdi, unsigned int strict_limit);



/*

mm/page-writeback.c

+37 −0
Original line number Diff line number Diff line
@@ -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)

		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 u64 bdi_get_bytes(unsigned int ratio)

{

	unsigned long background_thresh;
@@ -722,6 +745,20 @@ u64 bdi_get_max_bytes(struct backing_dev_info *bdi) 
	return bdi_get_bytes(bdi->max_ratio);

}



int bdi_set_max_bytes(struct backing_dev_info *bdi, u64 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);

}



int bdi_set_strict_limit(struct backing_dev_info *bdi, unsigned int strict_limit)

{

	if (strict_limit > 1)