1 files changed, 39 insertions, 34 deletions

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 23bb0ceabe31..412593703d1e 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -5,6 +5,7 @@
 #include <linux/mm.h>
 #include <linux/pagemap.h>
 #include <linux/writeback.h>    /* generic_writepages */
+#include <linux/slab.h>
 #include <linux/pagevec.h>
 #include <linux/task_io_accounting_ops.h>
 
@@ -336,16 +337,15 @@ out:
 /*
  * Get ref for the oldest snapc for an inode with dirty data... that is, the
  * only snap context we are allowed to write back.
- *
- * Caller holds i_lock.
  */
-static struct ceph_snap_context *__get_oldest_context(struct inode *inode,
-                                                      u64 *snap_size)
+static struct ceph_snap_context *get_oldest_context(struct inode *inode,
+                                                    u64 *snap_size)
 {
         struct ceph_inode_info *ci = ceph_inode(inode);
         struct ceph_snap_context *snapc = NULL;
         struct ceph_cap_snap *capsnap = NULL;
 
+        spin_lock(&inode->i_lock);
         list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
                 dout(" cap_snap %p snapc %p has %d dirty pages\n", capsnap,
                      capsnap->context, capsnap->dirty_pages);
@@ -356,21 +356,11 @@ static struct ceph_snap_context *__get_oldest_context(struct inode *inode,
                         break;
                 }
         }
-        if (!snapc && ci->i_snap_realm) {
-                snapc = ceph_get_snap_context(ci->i_snap_realm->cached_context);
+        if (!snapc && ci->i_head_snapc) {
+                snapc = ceph_get_snap_context(ci->i_head_snapc);
                 dout(" head snapc %p has %d dirty pages\n",
                      snapc, ci->i_wrbuffer_ref_head);
         }
-        return snapc;
-}
-
-static struct ceph_snap_context *get_oldest_context(struct inode *inode,
-                                                    u64 *snap_size)
-{
-        struct ceph_snap_context *snapc = NULL;
-
-        spin_lock(&inode->i_lock);
-        snapc = __get_oldest_context(inode, snap_size);
         spin_unlock(&inode->i_lock);
         return snapc;
 }
@@ -391,7 +381,7 @@ static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
         int len = PAGE_CACHE_SIZE;
         loff_t i_size;
         int err = 0;
-        struct ceph_snap_context *snapc;
+        struct ceph_snap_context *snapc, *oldest;
         u64 snap_size = 0;
         long writeback_stat;
 
@@ -412,13 +402,16 @@ static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
                 dout("writepage %p page %p not dirty?\n", inode, page);
                 goto out;
         }
-        if (snapc != get_oldest_context(inode, &snap_size)) {
+        oldest = get_oldest_context(inode, &snap_size);
+        if (snapc->seq > oldest->seq) {
                 dout("writepage %p page %p snapc %p not writeable - noop\n",
                      inode, page, (void *)page->private);
                 /* we should only noop if called by kswapd */
                 WARN_ON((current->flags & PF_MEMALLOC) == 0);
+                ceph_put_snap_context(oldest);
                 goto out;
         }
+        ceph_put_snap_context(oldest);
 
         /* is this a partial page at end of file? */
         if (snap_size)
@@ -457,7 +450,7 @@ static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
         ClearPagePrivate(page);
         end_page_writeback(page);
         ceph_put_wrbuffer_cap_refs(ci, 1, snapc);
-        ceph_put_snap_context(snapc);
+        ceph_put_snap_context(snapc);  /* page's reference */
 out:
         return err;
 }
@@ -557,9 +550,9 @@ static void writepages_finish(struct ceph_osd_request *req,
                         dout("inode %p skipping page %p\n", inode, page);
                         wbc->pages_skipped++;
                 }
+                ceph_put_snap_context((void *)page->private);
                 page->private = 0;
                 ClearPagePrivate(page);
-                ceph_put_snap_context(snapc);
                 dout("unlocking %d %p\n", i, page);
                 end_page_writeback(page);
 
@@ -617,7 +610,7 @@ static int ceph_writepages_start(struct address_space *mapping,
         int range_whole = 0;
         int should_loop = 1;
         pgoff_t max_pages = 0, max_pages_ever = 0;
-        struct ceph_snap_context *snapc = NULL, *last_snapc = NULL;
+        struct ceph_snap_context *snapc = NULL, *last_snapc = NULL, *pgsnapc;
         struct pagevec pvec;
         int done = 0;
         int rc = 0;
@@ -769,9 +762,10 @@ get_more_pages:
                         }
 
                         /* only if matching snap context */
-                        if (snapc != (void *)page->private) {
-                                dout("page snapc %p != oldest %p\n",
-                                     (void *)page->private, snapc);
+                        pgsnapc = (void *)page->private;
+                        if (pgsnapc->seq > snapc->seq) {
+                                dout("page snapc %p %lld > oldest %p %lld\n",
+                                     pgsnapc, pgsnapc->seq, snapc, snapc->seq);
                                 unlock_page(page);
                                 if (!locked_pages)
                                         continue; /* keep looking for snap */
@@ -913,12 +907,19 @@ static int context_is_writeable_or_written(struct inode *inode,
                                            struct ceph_snap_context *snapc)
 {
         struct ceph_snap_context *oldest = get_oldest_context(inode, NULL);
-        return !oldest || snapc->seq <= oldest->seq;
+        int ret = !oldest || snapc->seq <= oldest->seq;
+
+        ceph_put_snap_context(oldest);
+        return ret;
 }
 
 /*
  * We are only allowed to write into/dirty the page if the page is
  * clean, or already dirty within the same snap context.
+ *
+ * called with page locked.
+ * return success with page locked,
+ * or any failure (incl -EAGAIN) with page unlocked.
  */
 static int ceph_update_writeable_page(struct file *file,
                             loff_t pos, unsigned len,
@@ -931,8 +932,8 @@ static int ceph_update_writeable_page(struct file *file,
         int pos_in_page = pos & ~PAGE_CACHE_MASK;
         int end_in_page = pos_in_page + len;
         loff_t i_size;
-        struct ceph_snap_context *snapc;
         int r;
+        struct ceph_snap_context *snapc, *oldest;
 
 retry_locked:
         /* writepages currently holds page lock, but if we change that later, */
@@ -942,30 +943,34 @@ retry_locked:
         BUG_ON(!ci->i_snap_realm);
         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) {
+        snapc = (void *)page->private;
+        if (snapc && snapc != ci->i_head_snapc) {
                 /*
                  * this page is already dirty in another (older) snap
                  * context!  is it writeable now?
                  */
-                snapc = get_oldest_context(inode, NULL);
+                oldest = get_oldest_context(inode, NULL);
                 up_read(&mdsc->snap_rwsem);
 
-                if (snapc != (void *)page->private) {
+                if (snapc->seq > oldest->seq) {
+                        ceph_put_snap_context(oldest);
                         dout(" page %p snapc %p not current or oldest\n",
-                             page, (void *)page->private);
+                             page, snapc);
                         /*
                          * queue for writeback, and wait for snapc to
                          * be writeable or written
                          */
-                        snapc = ceph_get_snap_context((void *)page->private);
+                        snapc = ceph_get_snap_context(snapc);
                         unlock_page(page);
                         ceph_queue_writeback(inode);
-                        wait_event_interruptible(ci->i_cap_wq,
+                        r = wait_event_interruptible(ci->i_cap_wq,
                                context_is_writeable_or_written(inode, snapc));
                         ceph_put_snap_context(snapc);
+                        if (r == -ERESTARTSYS)
+                                return r;
                         return -EAGAIN;
                 }
+                ceph_put_snap_context(oldest);
 
                 /* yay, writeable, do it now (without dropping page lock) */
                 dout(" page %p snapc %p not current, but oldest\n",
@@ -1035,7 +1040,7 @@ static int ceph_write_begin(struct file *file, struct address_space *mapping,
         int r;
 
         do {
-                /* get a page*/
+                /* get a page */
                 page = grab_cache_page_write_begin(mapping, index, 0);
                 if (!page)
                         return -ENOMEM;