Merge git://git.kernel.org/pub/scm/linux/kernel/git/sfrench/cifs-2.6

* git://git.kernel.org/pub/scm/linux/kernel/git/sfrench/cifs-2.6:
  [CIFS] fix regression in cifs_write_begin/cifs_write_end

1 files changed, 56 insertions, 21 deletions

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index b691b893a848..f0a81e631ae6 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -1475,7 +1475,11 @@ static int cifs_write_end(struct file *file, struct address_space *mapping,
         cFYI(1, ("write_end for page %p from pos %lld with %d bytes",
                  page, pos, copied));
 
-        if (!PageUptodate(page) && copied == PAGE_CACHE_SIZE)
+        if (PageChecked(page)) {
+                if (copied == len)
+                        SetPageUptodate(page);
+                ClearPageChecked(page);
+        } else if (!PageUptodate(page) && copied == PAGE_CACHE_SIZE)
                 SetPageUptodate(page);
 
         if (!PageUptodate(page)) {
@@ -2062,39 +2066,70 @@ static int cifs_write_begin(struct file *file, struct address_space *mapping,
 {
         pgoff_t index = pos >> PAGE_CACHE_SHIFT;
         loff_t offset = pos & (PAGE_CACHE_SIZE - 1);
+        loff_t page_start = pos & PAGE_MASK;
+        loff_t i_size;
+        struct page *page;
+        int rc = 0;
 
         cFYI(1, ("write_begin from %lld len %d", (long long)pos, len));
 
-        *pagep = __grab_cache_page(mapping, index);
-        if (!*pagep)
-                return -ENOMEM;
-
-        if (PageUptodate(*pagep))
-                return 0;
+        page = __grab_cache_page(mapping, index);
+        if (!page) {
+                rc = -ENOMEM;
+                goto out;
+        }
 
-        /* If we are writing a full page it will be up to date,
-           no need to read from the server */
-        if (len == PAGE_CACHE_SIZE && flags & AOP_FLAG_UNINTERRUPTIBLE)
-                return 0;
+        if (PageUptodate(page))
+                goto out;
 
-        if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
-                int rc;
+        /*
+         * If we write a full page it will be up to date, no need to read from
+         * the server. If the write is short, we'll end up doing a sync write
+         * instead.
+         */
+        if (len == PAGE_CACHE_SIZE)
+                goto out;
 
-                /* might as well read a page, it is fast enough */
-                rc = cifs_readpage_worker(file, *pagep, &offset);
+        /*
+         * optimize away the read when we have an oplock, and we're not
+         * expecting to use any of the data we'd be reading in. That
+         * is, when the page lies beyond the EOF, or straddles the EOF
+         * and the write will cover all of the existing data.
+         */
+        if (CIFS_I(mapping->host)->clientCanCacheRead) {
+                i_size = i_size_read(mapping->host);
+                if (page_start >= i_size ||
+                    (offset == 0 && (pos + len) >= i_size)) {
+                        zero_user_segments(page, 0, offset,
+                                           offset + len,
+                                           PAGE_CACHE_SIZE);
+                        /*
+                         * PageChecked means that the parts of the page
+                         * to which we're not writing are considered up
+                         * to date. Once the data is copied to the
+                         * page, it can be set uptodate.
+                         */
+                        SetPageChecked(page);
+                        goto out;
+                }
+        }
 
-                /* we do not need to pass errors back
-                   e.g. if we do not have read access to the file
-                   because cifs_write_end will attempt synchronous writes
-                   -- shaggy */
+        if ((file->f_flags & O_ACCMODE) != O_WRONLY) {
+                /*
+                 * might as well read a page, it is fast enough. If we get
+                 * an error, we don't need to return it. cifs_write_end will
+                 * do a sync write instead since PG_uptodate isn't set.
+                 */
+                cifs_readpage_worker(file, page, &page_start);
         } else {
                 /* we could try using another file handle if there is one -
                    but how would we lock it to prevent close of that handle
                    racing with this read? In any case
                    this will be written out by write_end so is fine */
         }
-
-        return 0;
+out:
+        *pagep = page;
+        return rc;
 }
 
 const struct address_space_operations cifs_addr_ops = {