Revert "[XFS] remove old vmap cache"

This reverts commit d2859751cd0bf586941ffa7308635a293f943c17.

This commit caused regression. We'll try to fix use of new
vmap API for next release.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

1 files changed, 74 insertions, 1 deletions

diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c
index 0b2177a9fbdc..cb329edc925b 100644
--- a/fs/xfs/linux-2.6/xfs_buf.c
+++ b/fs/xfs/linux-2.6/xfs_buf.c
@@ -166,6 +166,75 @@ test_page_region(
 }
 
 /*
+ *      Mapping of multi-page buffers into contiguous virtual space
+ */
+
+typedef struct a_list {
+        void            *vm_addr;
+        struct a_list   *next;
+} a_list_t;
+
+static a_list_t         *as_free_head;
+static int              as_list_len;
+static DEFINE_SPINLOCK(as_lock);
+
+/*
+ *      Try to batch vunmaps because they are costly.
+ */
+STATIC void
+free_address(
+        void            *addr)
+{
+        a_list_t        *aentry;
+
+#ifdef CONFIG_XEN
+        /*
+         * Xen needs to be able to make sure it can get an exclusive
+         * RO mapping of pages it wants to turn into a pagetable.  If
+         * a newly allocated page is also still being vmap()ed by xfs,
+         * it will cause pagetable construction to fail.  This is a
+         * quick workaround to always eagerly unmap pages so that Xen
+         * is happy.
+         */
+        vunmap(addr);
+        return;
+#endif
+
+        aentry = kmalloc(sizeof(a_list_t), GFP_NOWAIT);
+        if (likely(aentry)) {
+                spin_lock(&as_lock);
+                aentry->next = as_free_head;
+                aentry->vm_addr = addr;
+                as_free_head = aentry;
+                as_list_len++;
+                spin_unlock(&as_lock);
+        } else {
+                vunmap(addr);
+        }
+}
+
+STATIC void
+purge_addresses(void)
+{
+        a_list_t        *aentry, *old;
+
+        if (as_free_head == NULL)
+                return;
+
+        spin_lock(&as_lock);
+        aentry = as_free_head;
+        as_free_head = NULL;
+        as_list_len = 0;
+        spin_unlock(&as_lock);
+
+        while ((old = aentry) != NULL) {
+                vunmap(aentry->vm_addr);
+                aentry = aentry->next;
+                kfree(old);
+        }
+}
+
+/*
  *      Internal xfs_buf_t object manipulation
  */
 
@@ -264,7 +333,7 @@ xfs_buf_free(
                 uint            i;
 
                 if ((bp->b_flags & XBF_MAPPED) && (bp->b_page_count > 1))
-                       vunmap(bp->b_addr - bp->b_offset);
+                        free_address(bp->b_addr - bp->b_offset);
 
                 for (i = 0; i < bp->b_page_count; i++) {
                         struct page     *page = bp->b_pages[i];
@@ -386,6 +455,8 @@ _xfs_buf_map_pages(
                 bp->b_addr = page_address(bp->b_pages[0]) + bp->b_offset;
                 bp->b_flags |= XBF_MAPPED;
         } else if (flags & XBF_MAPPED) {
+                if (as_list_len > 64)
+                        purge_addresses();
                 bp->b_addr = vmap(bp->b_pages, bp->b_page_count,
                                         VM_MAP, PAGE_KERNEL);
                 if (unlikely(bp->b_addr == NULL))
@@ -1672,6 +1743,8 @@ xfsbufd(
                         count++;
                 }
 
+                if (as_list_len > 0)
+                        purge_addresses();
                 if (count)
                         blk_run_address_space(target->bt_mapping);