[XFS] cluster rewrites We can cluster mapped pages aswell, this improves

performances on rewrites since we can reduce the number of allocator
calls.

SGI-PV: 947118
SGI-Modid: xfs-linux-melb:xfs-kern:203829a

Signed-off-by: Christoph Hellwig <hch@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>

1 files changed, 47 insertions, 16 deletions

diff --git a/fs/xfs/linux-2.6/xfs_aops.c b/fs/xfs/linux-2.6/xfs_aops.c
index 562867316639..9ea33ea6a225 100644
--- a/fs/xfs/linux-2.6/xfs_aops.c
+++ b/fs/xfs/linux-2.6/xfs_aops.c
@@ -470,13 +470,13 @@ xfs_map_at_offset(
 }
 
 /*
- * Look for a page at index which is unlocked and not mapped
- * yet - clustering for mmap write case.
+ * Look for a page at index that is suitable for clustering.
  */
 STATIC unsigned int
-xfs_probe_unmapped_page(
+xfs_probe_page(
         struct page             *page,
-        unsigned int            pg_offset)
+        unsigned int            pg_offset,
+        int                     mapped)
 {
         int                     ret = 0;
 
@@ -489,25 +489,28 @@ xfs_probe_unmapped_page(
 
                         bh = head = page_buffers(page);
                         do {
-                                if (buffer_mapped(bh) || !buffer_uptodate(bh))
+                                if (!buffer_uptodate(bh))
+                                        break;
+                                if (mapped != buffer_mapped(bh))
                                         break;
                                 ret += bh->b_size;
                                 if (ret >= pg_offset)
                                         break;
                         } while ((bh = bh->b_this_page) != head);
                 } else
-                        ret = PAGE_CACHE_SIZE;
+                        ret = mapped ? 0 : PAGE_CACHE_SIZE;
         }
 
         return ret;
 }
 
 STATIC size_t
-xfs_probe_unmapped_cluster(
+xfs_probe_cluster(
         struct inode            *inode,
         struct page             *startpage,
         struct buffer_head      *bh,
-        struct buffer_head      *head)
+        struct buffer_head      *head,
+        int                     mapped)
 {
         struct pagevec          pvec;
         pgoff_t                 tindex, tlast, tloff;
@@ -516,7 +519,7 @@ xfs_probe_unmapped_cluster(
 
         /* First sum forwards in this page */
         do {
-                if (buffer_mapped(bh))
+                if (mapped != buffer_mapped(bh))
                         return total;
                 total += bh->b_size;
         } while ((bh = bh->b_this_page) != head);
@@ -550,7 +553,7 @@ xfs_probe_unmapped_cluster(
                                 pg_offset = PAGE_CACHE_SIZE;
 
                         if (page->index == tindex && !TestSetPageLocked(page)) {
-                                len = xfs_probe_unmapped_page(page, pg_offset);
+                                len = xfs_probe_page(page, pg_offset, mapped);
                                 unlock_page(page);
                         }
 
@@ -592,6 +595,8 @@ xfs_is_delayed_page(
                                 acceptable = (type == IOMAP_UNWRITTEN);
                         else if (buffer_delay(bh))
                                 acceptable = (type == IOMAP_DELAY);
+                        else if (buffer_mapped(bh))
+                                acceptable = (type == 0);
                         else
                                 break;
                 } while ((bh = bh->b_this_page) != head);
@@ -804,6 +809,7 @@ xfs_page_state_convert(
         ssize_t                 size, len;
         int                     flags, err, iomap_valid = 0, uptodate = 1;
         int                     page_dirty, count = 0, trylock_flag = 0;
+        int                     all_bh = unmapped;
 
         /* wait for other IO threads? */
         if (startio && wbc->sync_mode != WB_SYNC_NONE)
@@ -845,6 +851,8 @@ xfs_page_state_convert(
 
         bh = head = page_buffers(page);
         offset = page_offset(page);
+        flags = -1;
+        type = 0;
 
         /* TODO: cleanup count and page_dirty */
 
@@ -878,6 +886,12 @@ xfs_page_state_convert(
                 if (buffer_unwritten(bh) || buffer_delay(bh) ||
                     ((buffer_uptodate(bh) || PageUptodate(page)) &&
                      !buffer_mapped(bh) && (unmapped || startio))) {
+                        /*
+                         * Make sure we don't use a read-only iomap
+                         */
+                        if (flags == BMAPI_READ)
+                                iomap_valid = 0;
+
                         if (buffer_unwritten(bh)) {
                                 type = IOMAP_UNWRITTEN;
                                 flags = BMAPI_WRITE|BMAPI_IGNSTATE;
@@ -887,14 +901,14 @@ xfs_page_state_convert(
                                 if (!startio)
                                         flags |= trylock_flag;
                         } else {
-                                type = 0;
+                                type = IOMAP_NEW;
                                 flags = BMAPI_WRITE|BMAPI_MMAP;
                         }
 
                         if (!iomap_valid) {
-                                if (type == 0) {
-                                        size = xfs_probe_unmapped_cluster(inode,
-                                                        page, bh, head);
+                                if (type == IOMAP_NEW) {
+                                        size = xfs_probe_cluster(inode,
+                                                        page, bh, head, 0);
                                 } else {
                                         size = len;
                                 }
@@ -921,10 +935,27 @@ xfs_page_state_convert(
                                 count++;
                         }
                 } else if (buffer_uptodate(bh) && startio) {
-                        type = 0;
+                        /*
+                         * we got here because the buffer is already mapped.
+                         * That means it must already have extents allocated
+                         * underneath it. Map the extent by reading it.
+                         */
+                        if (!iomap_valid || type != 0) {
+                                flags = BMAPI_READ;
+                                size = xfs_probe_cluster(inode, page, bh,
+                                                                head, 1);
+                                err = xfs_map_blocks(inode, offset, size,
+                                                &iomap, flags);
+                                if (err)
+                                        goto error;
+                                iomap_valid = xfs_iomap_valid(&iomap, offset);
+                        }
 
+                        type = 0;
                         if (!test_and_set_bit(BH_Lock, &bh->b_state)) {
                                 ASSERT(buffer_mapped(bh));
+                                if (iomap_valid)
+                                        all_bh = 1;
                                 xfs_add_to_ioend(inode, bh, offset, type,
                                                 &ioend, !iomap_valid);
                                 page_dirty--;
@@ -953,7 +984,7 @@ xfs_page_state_convert(
                                         PAGE_CACHE_SHIFT;
                 tlast = min_t(pgoff_t, offset, last_index);
                 xfs_cluster_write(inode, page->index + 1, &iomap, &ioend,
-                                        wbc, startio, unmapped, tlast);
+                                        wbc, startio, all_bh, tlast);
         }
 
         if (iohead)