ecryptfs: modify write path to encrypt page in writepage

Change the write path to encrypt the data only when the page is written to
disk in ecryptfs_writepage. Previously, ecryptfs encrypts the page in
ecryptfs_write_end which means that if there are multiple write requests to
the same page, ecryptfs ends up re-encrypting that page over and over again.
This patch minimizes the number of encryptions needed.

Signed-off-by: Thieu Le <thieule@chromium.org>
[tyhicks: Changed NULL .drop_inode sop pointer to generic_drop_inode]
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

1 files changed, 27 insertions, 14 deletions

diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
index 519af27db059..5e150131eb9d 100644
--- a/fs/ecryptfs/mmap.c
+++ b/fs/ecryptfs/mmap.c
@@ -62,6 +62,18 @@ static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
 {
         int rc;
 
+        /*
+         * Refuse to write the page out if we are called from reclaim context
+         * since our writepage() path may potentially allocate memory when
+         * calling into the lower fs vfs_write() which may in turn invoke
+         * us again.
+         */
+        if (current->flags & PF_MEMALLOC) {
+                redirty_page_for_writepage(wbc, page);
+                rc = 0;
+                goto out;
+        }
+
         rc = ecryptfs_encrypt_page(page);
         if (rc) {
                 ecryptfs_printk(KERN_WARNING, "Error encrypting "
@@ -70,8 +82,8 @@ static int ecryptfs_writepage(struct page *page, struct writeback_control *wbc)
                 goto out;
         }
         SetPageUptodate(page);
-        unlock_page(page);
 out:
+        unlock_page(page);
         return rc;
 }
 
@@ -481,6 +493,7 @@ static int ecryptfs_write_end(struct file *file,
         struct ecryptfs_crypt_stat *crypt_stat =
                 &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat;
         int rc;
+        int need_unlock_page = 1;
 
         ecryptfs_printk(KERN_DEBUG, "Calling fill_zeros_to_end_of_page"
                         "(page w/ index = [0x%.16lx], to = [%d])\n", index, to);
@@ -501,26 +514,26 @@ static int ecryptfs_write_end(struct file *file,
                         "zeros in page with index = [0x%.16lx]\n", index);
                 goto out;
         }
-        rc = ecryptfs_encrypt_page(page);
-        if (rc) {
-                ecryptfs_printk(KERN_WARNING, "Error encrypting page (upper "
-                                "index [0x%.16lx])\n", index);
-                goto out;
-        }
+        set_page_dirty(page);
+        unlock_page(page);
+        need_unlock_page = 0;
         if (pos + copied > i_size_read(ecryptfs_inode)) {
                 i_size_write(ecryptfs_inode, pos + copied);
                 ecryptfs_printk(KERN_DEBUG, "Expanded file size to "
                         "[0x%.16llx]\n",
                         (unsigned long long)i_size_read(ecryptfs_inode));
+                balance_dirty_pages_ratelimited(mapping);
+                rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
+                if (rc) {
+                        printk(KERN_ERR "Error writing inode size to metadata; "
+                               "rc = [%d]\n", rc);
+                        goto out;
+                }
         }
-        rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
-        if (rc)
-                printk(KERN_ERR "Error writing inode size to metadata; "
-                       "rc = [%d]\n", rc);
-        else
-                rc = copied;
+        rc = copied;
 out:
-        unlock_page(page);
+        if (need_unlock_page)
+                unlock_page(page);
         page_cache_release(page);
         return rc;
 }