[PATCH] swap: scan_swap_map drop swap_device_lock

[linux-2.6] / mm / swapfile.c

diff --git a/mm/swapfile.c b/mm/swapfile.c
index c70248aab536cdfdcf97fcfaf4508b23fd75f823..fdee145afc6ff187f407f8ada1dd05e0a40c5cc4 100644 (file)
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -98,10 +98,12 @@ static inline unsigned long scan_swap_map(struct swap_info_struct *si)
         * But we do now try to find an empty cluster.  -Andrea
         */
 
+       si->flags += SWP_SCANNING;
        if (unlikely(!si->cluster_nr)) {
                si->cluster_nr = SWAPFILE_CLUSTER - 1;
                if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER)
                        goto lowest;
+               swap_device_unlock(si);
 
                offset = si->lowest_bit;
                last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
@@ -111,10 +113,12 @@ static inline unsigned long scan_swap_map(struct swap_info_struct *si)
                        if (si->swap_map[offset])
                                last_in_cluster = offset + SWAPFILE_CLUSTER;
                        else if (offset == last_in_cluster) {
+                               swap_device_lock(si);
                                si->cluster_next = offset-SWAPFILE_CLUSTER-1;
                                goto cluster;
                        }
                }
+               swap_device_lock(si);
                goto lowest;
        }
 
@@ -123,10 +127,12 @@ cluster:
        offset = si->cluster_next;
        if (offset > si->highest_bit)
 lowest:                offset = si->lowest_bit;
+checks:        if (!(si->flags & SWP_WRITEOK))
+               goto no_page;
        if (!si->highest_bit)
                goto no_page;
        if (!si->swap_map[offset]) {
-got_page:      if (offset == si->lowest_bit)
+               if (offset == si->lowest_bit)
                        si->lowest_bit++;
                if (offset == si->highest_bit)
                        si->highest_bit--;
@@ -137,16 +143,22 @@ got_page: if (offset == si->lowest_bit)
                }
                si->swap_map[offset] = 1;
                si->cluster_next = offset + 1;
+               si->flags -= SWP_SCANNING;
                return offset;
        }
 
+       swap_device_unlock(si);
        while (++offset <= si->highest_bit) {
-               if (!si->swap_map[offset])
-                       goto got_page;
+               if (!si->swap_map[offset]) {
+                       swap_device_lock(si);
+                       goto checks;
+               }
        }
+       swap_device_lock(si);
        goto lowest;
 
 no_page:
+       si->flags -= SWP_SCANNING;
        return 0;
 }
 
@@ -1111,10 +1123,6 @@ asmlinkage long sys_swapoff(const char __user * specialfile)
        err = try_to_unuse(type);
        current->flags &= ~PF_SWAPOFF;
 
-       /* wait for any unplug function to finish */
-       down_write(&swap_unplug_sem);
-       up_write(&swap_unplug_sem);
-
        if (err) {
                /* re-insert swap space back into swap_list */
                swap_list_lock();
@@ -1128,10 +1136,28 @@ asmlinkage long sys_swapoff(const char __user * specialfile)
                        swap_info[prev].next = p - swap_info;
                nr_swap_pages += p->pages;
                total_swap_pages += p->pages;
+               swap_device_lock(p);
                p->flags |= SWP_WRITEOK;
+               swap_device_unlock(p);
                swap_list_unlock();
                goto out_dput;
        }
+
+       /* wait for any unplug function to finish */
+       down_write(&swap_unplug_sem);
+       up_write(&swap_unplug_sem);
+
+       /* wait for anyone still in scan_swap_map */
+       swap_device_lock(p);
+       p->highest_bit = 0;             /* cuts scans short */
+       while (p->flags >= SWP_SCANNING) {
+               swap_device_unlock(p);
+               set_current_state(TASK_UNINTERRUPTIBLE);
+               schedule_timeout(1);
+               swap_device_lock(p);
+       }
+       swap_device_unlock(p);
+
        destroy_swap_extents(p);
        down(&swapon_sem);
        swap_list_lock();
@@ -1431,6 +1457,8 @@ asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
                }
 
                p->lowest_bit  = 1;
+               p->cluster_next = 1;
+
                /*
                 * Find out how many pages are allowed for a single swap
                 * device. There are two limiting factors: 1) the number of