eCryptfs: delay writing 0's after llseek until write

[linux-2.6-omap-h63xx.git] / fs / ecryptfs / mmap.c

diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
index 88ea6697908f511a1eadeffc4ee04ce3f9f93cf4..55cec98a84e75cf490143af46302a9495993f158 100644 (file)
--- a/fs/ecryptfs/mmap.c
+++ b/fs/ecryptfs/mmap.c
@@ -376,9 +376,31 @@ out:
        return 0;
 }
 
+/**
+ * eCryptfs does not currently support holes. When writing after a
+ * seek past the end of the file, eCryptfs fills in 0's through to the
+ * current location. The code to fill in the 0's to all the
+ * intermediate pages calls ecryptfs_prepare_write_no_truncate().
+ */
+static int
+ecryptfs_prepare_write_no_truncate(struct file *file, struct page *page,
+                                  unsigned from, unsigned to)
+{
+       int rc = 0;
+
+       if (from == 0 && to == PAGE_CACHE_SIZE)
+               goto out;       /* If we are writing a full page, it will be
+                                  up to date. */
+       if (!PageUptodate(page))
+               rc = ecryptfs_do_readpage(file, page, page->index);
+out:
+       return rc;
+}
+
 static int ecryptfs_prepare_write(struct file *file, struct page *page,
                                  unsigned from, unsigned to)
 {
+       loff_t pos;
        int rc = 0;
 
        if (from == 0 && to == PAGE_CACHE_SIZE)
@@ -386,6 +408,16 @@ static int ecryptfs_prepare_write(struct file *file, struct page *page,
                                   up to date. */
        if (!PageUptodate(page))
                rc = ecryptfs_do_readpage(file, page, page->index);
+       pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
+       if (pos > i_size_read(page->mapping->host)) {
+               rc = ecryptfs_truncate(file->f_path.dentry, pos);
+               if (rc) {
+                       printk(KERN_ERR "Error on attempt to "
+                              "truncate to (higher) offset [%lld];"
+                              " rc = [%d]\n", pos, rc);
+                       goto out;
+               }
+       }
 out:
        return rc;
 }
@@ -744,10 +776,10 @@ int write_zeros(struct file *file, pgoff_t index, int start, int num_zeros)
                rc = PTR_ERR(tmp_page);
                goto out;
        }
-       rc = ecryptfs_prepare_write(file, tmp_page, start, start + num_zeros);
-       if (rc) {
+       if ((rc = ecryptfs_prepare_write_no_truncate(file, tmp_page, start,
+                                                    (start + num_zeros)))) {
                ecryptfs_printk(KERN_ERR, "Error preparing to write zero's "
-                               "to remainder of page at index [0x%.16x]\n",
+                               "to page at index [0x%.16x]\n",
                                index);
                page_cache_release(tmp_page);
                goto out;