kclient: writepage is noop if page is not oldest snapc

diff --git a/src/kernel/addr.c b/src/kernel/addr.c
index 41135f59d2051304e9daaf838bc8e15755d5f60b..b303507237c385f92d8110686b4392df472fc584 100644 (file)
--- a/src/kernel/addr.c
+++ b/src/kernel/addr.c
@@ -16,7 +16,7 @@ int ceph_debug_addr = -1;
 
 /*
  * if snapc is NULL, we are dirtying within the most recent (head) snap.
- * if snapc is non-NULL, we are redirtying a page withing a past snap,
+ * if snapc is non-NULL, we are redirtying a page within a past snap,
  * and need to adjust the count on the appropriate ceph_cap_snap.
  */
 static int ceph_set_page_dirty(struct page *page,
@@ -283,6 +283,37 @@ static int ceph_readpages(struct file *file, struct address_space *mapping,
        return 0;
 }
 
+/*
+ * get oldest snapc for inode with dirty data.. i.e., the only snap context
+ * we can actually write back.
+ */
+static struct ceph_snap_context *__get_oldest_context(struct inode *inode)
+{
+       struct ceph_inode_info *ci = ceph_inode(inode);
+       struct ceph_snap_context *snapc = 0;
+       struct list_head *p;
+       struct ceph_cap_snap *capsnap = 0;
+
+       spin_lock(&inode->i_lock);
+       list_for_each(p, &ci->i_cap_snaps) {
+               capsnap = list_entry(p, struct ceph_cap_snap, ci_item);
+               dout(20, " cap_snap %p has %d dirty pages\n", capsnap,
+                    capsnap->dirty);
+               if (capsnap->dirty)
+                       break;
+       }
+       if (capsnap && capsnap->dirty) {
+               snapc = ceph_get_snap_context(capsnap->context);
+       } else if (ci->i_snap_realm) {
+               snapc = ceph_get_snap_context(ci->i_snap_realm->cached_context);
+               dout(20, " head has %d dirty pages\n", ci->i_wrbuffer_ref_head);
+       }
+       spin_unlock(&inode->i_lock);
+
+       return snapc;
+}
+
+
 /*
  * ceph_writepage:
  *  clear dirty page, and set the writeback flag in the radix tree.
@@ -314,10 +345,26 @@ static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
        i_size = i_size_read(inode);
        if (i_size < page_off + len)
                len = i_size - page_off;
-       snapc = (void *)page->private;
-       dout(10, "writepage inode %p page %p index %lu on %llu~%u\n",
+       dout(10, "writepage %p page %p index %lu on %llu~%u\n",
             inode, page, page->index, page_off, len);
 
+       /* verify this is current snapc */
+       snapc = __get_oldest_context(inode);
+       if (!snapc) {
+               dout(20, "writepage %p page %p no snapc with dirty data?\n",
+                    inode, page);
+               goto out;
+       }
+       if ((void *)page->private == 0) {
+               dout(20, "writepage %p page %p not dirty?\n", inode, page);
+               goto out;
+       }
+       if ((void *)page->private != snapc) {
+               dout(10, "writepage %p page %p snapc %p newer than %p - noop\n",
+                    inode, page, (void *)page->private, snapc);
+               goto out;
+       }
+
        set_page_writeback(page);
        if (snapc) {
                err = ceph_osdc_writepages(osdc, ceph_vino(inode),
@@ -340,6 +387,7 @@ static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
                dout(20, "writepage %p noop (no snapc)\n", page);
        }
        end_page_writeback(page);
+out:
        return err;
 }
 
@@ -387,8 +435,6 @@ static int ceph_writepages(struct address_space *mapping,
        int done = 0;
        int rc = 0;
        unsigned wsize = 1 << inode->i_blkbits;
-       struct list_head *p;
-       struct ceph_cap_snap *capsnap = 0;
 
        if (client->mount_args.wsize && client->mount_args.wsize < wsize)
                wsize = client->mount_args.wsize;
@@ -430,24 +476,8 @@ static int ceph_writepages(struct address_space *mapping,
 retry:
        /* find oldest snap context with dirty data */
        ceph_put_snap_context(snapc);
-       snapc = 0;
-
-       spin_lock(&inode->i_lock);
-       list_for_each(p, &ci->i_cap_snaps) {
-               capsnap = list_entry(p, struct ceph_cap_snap, ci_item);
-               dout(20, " cap_snap %p has %d dirty\n", capsnap,
-                    capsnap->dirty);
-               if (capsnap->dirty)
-                       break;
-       }
-       if (capsnap && capsnap->dirty) {
-               snapc = ceph_get_snap_context(capsnap->context);
-       } else if (ci->i_snap_realm) {
-               snapc = ceph_get_snap_context(ci->i_snap_realm->cached_context);
-               dout(20, " %d head wrbuffer refs\n", ci->i_wrbuffer_ref_head);
-       }
-       spin_unlock(&inode->i_lock);
 
+       snapc = __get_oldest_context(inode);
        if (!snapc) {
                /* hmm, why does writepages get called when there
                   is no dirty data? */
@@ -701,8 +731,8 @@ static int ceph_write_begin(struct file *file, struct address_space *mapping,
 
        /* check snap context */
        BUG_ON(!ci->i_snap_realm);
-       BUG_ON(!ci->i_snap_realm->cached_context);
        down_read(&mdsc->snap_rwsem);
+       BUG_ON(!ci->i_snap_realm->cached_context);
        if (page->private &&
            (void *)page->private != ci->i_snap_realm->cached_context) {
                /* force early writeback of snapped page */