exofs: Optimize read_4_write

Don't attempt a read passed i_size, just zero the page and be
done with it.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>

1 files changed, 22 insertions, 3 deletions

diff --git a/fs/exofs/inode.c b/fs/exofs/inode.c
index a7555238c41a..c8f58a96e597 100644
--- a/fs/exofs/inode.c
+++ b/fs/exofs/inode.c
@@ -350,8 +350,10 @@ static int readpage_strip(void *data, struct page *page)
 
                 if (!pcol->read_4_write)
                         unlock_page(page);
-                EXOFS_DBGMSG("readpage_strip(0x%lx, 0x%lx) empty page,"
-                             " splitting\n", inode->i_ino, page->index);
+                EXOFS_DBGMSG("readpage_strip(0x%lx) empty page len=%zx "
+                             "read_4_write=%d index=0x%lx end_index=0x%lx "
+                             "splitting\n", inode->i_ino, len,
+                             pcol->read_4_write, page->index, end_index);
 
                 return read_exec(pcol);
         }
@@ -722,11 +724,28 @@ int exofs_write_begin(struct file *file, struct address_space *mapping,
 
          /* read modify write */
         if (!PageUptodate(page) && (len != PAGE_CACHE_SIZE)) {
+                loff_t i_size = i_size_read(mapping->host);
+                pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
+                size_t rlen;
+
+                if (page->index < end_index)
+                        rlen = PAGE_CACHE_SIZE;
+                else if (page->index == end_index)
+                        rlen = i_size & ~PAGE_CACHE_MASK;
+                else
+                        rlen = 0;
+
+                if (!rlen) {
+                        clear_highpage(page);
+                        SetPageUptodate(page);
+                        goto out;
+                }
+
                 ret = _readpage(page, true);
                 if (ret) {
                         /*SetPageError was done by _readpage. Is it ok?*/
                         unlock_page(page);
-                        EXOFS_DBGMSG("__readpage_filler failed\n");
+                        EXOFS_DBGMSG("__readpage failed\n");
                 }
         }
 out: