From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Subject: mm/vmscan: replace implicit RECLAIM_ZONE checks with explicit checks RECLAIM_ZONE was assumed to be unused because it was never explicitly used in the kernel. However, there were a number of places where it was checked implicitly by checking 'node_reclaim_mode' for a zero value. These zero checks are not great because it is not obvious what a zero mode *means* in the code. Replace them with a helper which makes it more obvious: node_reclaim_enabled(). This helper also provides a handy place to explicitly check the RECLAIM_ZONE bit itself. Check it explicitly there to make it more obvious where the bit can affect behavior. This should have no functional impact. Link: https://lkml.kernel.org/r/20210219172559.BF589C44@xxxxxxxxxxxxxxxxxx Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Reviewed-by: Ben Widawsky <ben.widawsky@xxxxxxxxx> Reviewed-by: Oscar Salvador <osalvador@xxxxxxx> Acked-by: Christoph Lameter <cl@xxxxxxxxx> Acked-by: David Rientjes <rientjes@xxxxxxxxxx> Cc: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx> Cc: "Tobin C. Harding" <tobin@xxxxxxxxxx> Cc: Huang Ying <ying.huang@xxxxxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: Qian Cai <cai@xxxxxx> Cc: Daniel Wagner <dwagner@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/swap.h | 7 +++++++ mm/khugepaged.c | 2 +- mm/page_alloc.c | 2 +- 3 files changed, 9 insertions(+), 2 deletions(-) --- a/include/linux/swap.h~mm-vmscan-replace-implicit-reclaim_zone-checks-with-explicit-checks +++ a/include/linux/swap.h @@ -12,6 +12,7 @@ #include <linux/fs.h> #include <linux/atomic.h> #include <linux/page-flags.h> +#include <uapi/linux/mempolicy.h> #include <asm/page.h> struct notifier_block; @@ -378,6 +379,12 @@ extern int sysctl_min_slab_ratio; #define node_reclaim_mode 0 #endif +static inline bool node_reclaim_enabled(void) +{ + /* Is any node_reclaim_mode bit set? */ + return node_reclaim_mode & (RECLAIM_ZONE|RECLAIM_WRITE|RECLAIM_UNMAP); +} + extern void check_move_unevictable_pages(struct pagevec *pvec); extern int kswapd_run(int nid); --- a/mm/khugepaged.c~mm-vmscan-replace-implicit-reclaim_zone-checks-with-explicit-checks +++ a/mm/khugepaged.c @@ -809,7 +809,7 @@ static bool khugepaged_scan_abort(int ni * If node_reclaim_mode is disabled, then no extra effort is made to * allocate memory locally. */ - if (!node_reclaim_mode) + if (!node_reclaim_enabled()) return false; /* If there is a count for this node already, it must be acceptable */ --- a/mm/page_alloc.c~mm-vmscan-replace-implicit-reclaim_zone-checks-with-explicit-checks +++ a/mm/page_alloc.c @@ -3968,7 +3968,7 @@ retry: if (alloc_flags & ALLOC_NO_WATERMARKS) goto try_this_zone; - if (node_reclaim_mode == 0 || + if (!node_reclaim_enabled() || !zone_allows_reclaim(ac->preferred_zoneref->zone, zone)) continue; _
