ceph: refactor ceph_write_begin, fix ceph_page_mkwrite

Originally ceph_page_mkwrite called ceph_write_begin, hoping that
the returned locked page would be the page that it was requested
to mkwrite. Factored out relevant part of ceph_page_mkwrite and
we lock the right page anyway.

Signed-off-by: Yehuda Sadeh <yehuda@hq.newdream.net>
Signed-off-by: Sage Weil <sage@newdream.net>

1 files changed, 51 insertions, 29 deletions

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 92f482150742..89c5ff3b59d5 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -907,15 +907,13 @@ static int context_is_writeable_or_written(struct inode *inode,
  * We are only allowed to write into/dirty the page if the page is
  * clean, or already dirty within the same snap context.
  */
-static int ceph_write_begin(struct file *file, struct address_space *mapping,
-                            loff_t pos, unsigned len, unsigned flags,
-                            struct page **pagep, void **fsdata)
+static int ceph_update_writeable_page(struct file *file,
+                            loff_t pos, unsigned len,
+                            struct page *page)
 {
         struct inode *inode = file->f_dentry->d_inode;
         struct ceph_inode_info *ci = ceph_inode(inode);
         struct ceph_mds_client *mdsc = &ceph_inode_to_client(inode)->mdsc;
-        struct page *page;
-        pgoff_t index = pos >> PAGE_CACHE_SHIFT;
         loff_t page_off = pos & PAGE_CACHE_MASK;
         int pos_in_page = pos & ~PAGE_CACHE_MASK;
         int end_in_page = pos_in_page + len;
@@ -923,16 +921,6 @@ static int ceph_write_begin(struct file *file, struct address_space *mapping,
         struct ceph_snap_context *snapc;
         int r;
 
-        /* get a page*/
-retry:
-        page = grab_cache_page_write_begin(mapping, index, 0);
-        if (!page)
-                return -ENOMEM;
-        *pagep = page;
-
-        dout("write_begin file %p inode %p page %p %d~%d\n", file,
-             inode, page, (int)pos, (int)len);
-
 retry_locked:
         /* writepages currently holds page lock, but if we change that later, */
         wait_on_page_writeback(page);
@@ -964,7 +952,7 @@ retry_locked:
                         wait_event_interruptible(ci->i_cap_wq,
                                context_is_writeable_or_written(inode, snapc));
                         ceph_put_snap_context(snapc);
-                        goto retry;
+                        return -EAGAIN;
                 }
 
                 /* yay, writeable, do it now (without dropping page lock) */
@@ -1022,6 +1010,35 @@ fail_nosnap:
 }
 
 /*
+ * We are only allowed to write into/dirty the page if the page is
+ * clean, or already dirty within the same snap context.
+ */
+static int ceph_write_begin(struct file *file, struct address_space *mapping,
+                            loff_t pos, unsigned len, unsigned flags,
+                            struct page **pagep, void **fsdata)
+{
+        struct inode *inode = file->f_dentry->d_inode;
+        struct page *page;
+        pgoff_t index = pos >> PAGE_CACHE_SHIFT;
+        int r;
+
+        do {
+                /* get a page*/
+                page = grab_cache_page_write_begin(mapping, index, 0);
+                if (!page)
+                        return -ENOMEM;
+                *pagep = page;
+
+                dout("write_begin file %p inode %p page %p %d~%d\n", file,
+                inode, page, (int)pos, (int)len);
+
+                r = ceph_update_writeable_page(file, pos, len, page);
+        } while (r == -EAGAIN);
+
+        return r;
+}
+
+/*
  * we don't do anything in here that simple_write_end doesn't do
  * except adjust dirty page accounting and drop read lock on
  * mdsc->snap_rwsem.
@@ -1104,8 +1121,6 @@ static int ceph_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
         struct ceph_mds_client *mdsc = &ceph_inode_to_client(inode)->mdsc;
         loff_t off = page->index << PAGE_CACHE_SHIFT;
         loff_t size, len;
-        struct page *locked_page = NULL;
-        void *fsdata = NULL;
         int ret;
 
         size = i_size_read(inode);
@@ -1116,23 +1131,30 @@ static int ceph_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 
         dout("page_mkwrite %p %llu~%llu page %p idx %lu\n", inode,
              off, len, page, page->index);
-        ret = ceph_write_begin(vma->vm_file, inode->i_mapping, off, len, 0,
-                               &locked_page, &fsdata);
-        WARN_ON(page != locked_page);
-        if (!ret) {
-                /*
-                 * doing the following, instead of calling
-                 * ceph_write_end. Note that we keep the
-                 * page locked
-                 */
+
+        lock_page(page);
+
+        ret = VM_FAULT_NOPAGE;
+        if ((off > size) ||
+            (page->mapping != inode->i_mapping))
+                goto out;
+
+        ret = ceph_update_writeable_page(vma->vm_file, off, len, page);
+        if (ret == 0) {
+                /* success.  we'll keep the page locked. */
                 set_page_dirty(page);
                 up_read(&mdsc->snap_rwsem);
-                page_cache_release(page);
                 ret = VM_FAULT_LOCKED;
         } else {
-                ret = VM_FAULT_SIGBUS;
+                if (ret == -ENOMEM)
+                        ret = VM_FAULT_OOM;
+                else
+                        ret = VM_FAULT_SIGBUS;
         }
+out:
         dout("page_mkwrite %p %llu~%llu = %d\n", inode, off, len, ret);
+        if (ret != VM_FAULT_LOCKED)
+                unlock_page(page);
         return ret;
 }