writeback: add general function domain_dirty_avail to calculate dirty and avail of...

Add general function domain_dirty_avail to calculate dirty and avail for
either dirty limit or background writeback in either global domain or wb
domain.

Link: https://lkml.kernel.org/r/20240514125254.142203-3-shikemeng@huaweicloud.com
Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 4e5d933..fe5d5a1 100644 (file)
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -837,6 +837,34 @@ static void mdtc_calc_avail(struct dirty_throttle_control *mdtc,
        mdtc->avail = filepages + min(headroom, other_clean);
 }
 
+static inline bool dtc_is_global(struct dirty_throttle_control *dtc)
+{
+       return mdtc_gdtc(dtc) == NULL;
+}
+
+/*
+ * Dirty background will ignore pages being written as we're trying to
+ * decide whether to put more under writeback.
+ */
+static void domain_dirty_avail(struct dirty_throttle_control *dtc,
+                              bool include_writeback)
+{
+       if (dtc_is_global(dtc)) {
+               dtc->avail = global_dirtyable_memory();
+               dtc->dirty = global_node_page_state(NR_FILE_DIRTY);
+               if (include_writeback)
+                       dtc->dirty += global_node_page_state(NR_WRITEBACK);
+       } else {
+               unsigned long filepages = 0, headroom = 0, writeback = 0;
+
+               mem_cgroup_wb_stats(dtc->wb, &filepages, &headroom, &dtc->dirty,
+                                   &writeback);
+               if (include_writeback)
+                       dtc->dirty += writeback;
+               mdtc_calc_avail(dtc, filepages, headroom);
+       }
+}
+
 /**
  * __wb_calc_thresh - @wb's share of dirty threshold
  * @dtc: dirty_throttle_context of interest
@@ -899,16 +927,9 @@ unsigned long cgwb_calc_thresh(struct bdi_writeback *wb)
 {
        struct dirty_throttle_control gdtc = { GDTC_INIT_NO_WB };
        struct dirty_throttle_control mdtc = { MDTC_INIT(wb, &gdtc) };
-       unsigned long filepages = 0, headroom = 0, writeback = 0;
 
-       gdtc.avail = global_dirtyable_memory();
-       gdtc.dirty = global_node_page_state(NR_FILE_DIRTY) +
-                    global_node_page_state(NR_WRITEBACK);
-
-       mem_cgroup_wb_stats(wb, &filepages, &headroom,
-                           &mdtc.dirty, &writeback);
-       mdtc.dirty += writeback;
-       mdtc_calc_avail(&mdtc, filepages, headroom);
+       domain_dirty_avail(&gdtc, true);
+       domain_dirty_avail(&mdtc, true);
        domain_dirty_limits(&mdtc);
 
        return __wb_calc_thresh(&mdtc, mdtc.thresh);
@@ -1719,9 +1740,8 @@ static int balance_dirty_pages(struct bdi_writeback *wb,
                unsigned long m_bg_thresh = 0;
 
                nr_dirty = global_node_page_state(NR_FILE_DIRTY);
-               gdtc->avail = global_dirtyable_memory();
-               gdtc->dirty = nr_dirty + global_node_page_state(NR_WRITEBACK);
 
+               domain_dirty_avail(gdtc, true);
                domain_dirty_limits(gdtc);
 
                if (unlikely(strictlimit)) {
@@ -1737,17 +1757,11 @@ static int balance_dirty_pages(struct bdi_writeback *wb,
                }
 
                if (mdtc) {
-                       unsigned long filepages, headroom, writeback;
-
                        /*
                         * If @wb belongs to !root memcg, repeat the same
                         * basic calculations for the memcg domain.
                         */
-                       mem_cgroup_wb_stats(wb, &filepages, &headroom,
-                                           &mdtc->dirty, &writeback);
-                       mdtc->dirty += writeback;
-                       mdtc_calc_avail(mdtc, filepages, headroom);
-
+                       domain_dirty_avail(mdtc, true);
                        domain_dirty_limits(mdtc);
 
                        if (unlikely(strictlimit)) {
@@ -2119,14 +2133,8 @@ bool wb_over_bg_thresh(struct bdi_writeback *wb)
        struct dirty_throttle_control * const mdtc = mdtc_valid(&mdtc_stor) ?
                                                     &mdtc_stor : NULL;
 
-       /*
-        * Similar to balance_dirty_pages() but ignores pages being written
-        * as we're trying to decide whether to put more under writeback.
-        */
-       gdtc->avail = global_dirtyable_memory();
-       gdtc->dirty = global_node_page_state(NR_FILE_DIRTY);
+       domain_dirty_avail(gdtc, false);
        domain_dirty_limits(gdtc);
-
        if (gdtc->dirty > gdtc->bg_thresh)
                return true;
 
@@ -2135,13 +2143,8 @@ bool wb_over_bg_thresh(struct bdi_writeback *wb)
                return true;
 
        if (mdtc) {
-               unsigned long filepages, headroom, writeback;
-
-               mem_cgroup_wb_stats(wb, &filepages, &headroom, &mdtc->dirty,
-                                   &writeback);
-               mdtc_calc_avail(mdtc, filepages, headroom);
+               domain_dirty_avail(mdtc, false);
                domain_dirty_limits(mdtc);      /* ditto, ignore writeback */
-
                if (mdtc->dirty > mdtc->bg_thresh)
                        return true;