[JFFS2][XATTR] Re-define xd->refcnt as atomic_t

In jffs2_release_xattr_datum(), it refers xd->refcnt to ensure
whether releasing xd is allowed or not.
But we can't hold xattr_sem since this function is called under
spin_lock(&c->erase_completion_lock). Thus we have to refer it
without any locking.

This patch redefine xd->refcnt as atomic_t. It enables to refer
xd->refcnt without any locking.

Signed-off-by: KaiGai Kohei <kaigai@ak.jp.nec.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

2 files changed, 12 insertions, 15 deletions

diff --git a/fs/jffs2/xattr.c b/fs/jffs2/xattr.c
index 7622f79cb5b4..18e66dbf23b4 100644
--- a/fs/jffs2/xattr.c
+++ b/fs/jffs2/xattr.c
@@ -345,7 +345,7 @@ static struct jffs2_xattr_datum *create_xattr_datum(struct jffs2_sb_info *c,
                     && xd->value_len==xsize
                     && !strcmp(xd->xname, xname)
                     && !memcmp(xd->xvalue, xvalue, xsize)) {
-                        xd->refcnt++;
+                        atomic_inc(&xd->refcnt);
                         return xd;
                 }
         }
@@ -365,7 +365,7 @@ static struct jffs2_xattr_datum *create_xattr_datum(struct jffs2_sb_info *c,
         strcpy(data, xname);
         memcpy(data + name_len + 1, xvalue, xsize);
 
-        xd->refcnt = 1;
+        atomic_set(&xd->refcnt, 1);
         xd->xid = ++c->highest_xid;
         xd->flags |= JFFS2_XFLAGS_HOT;
         xd->xprefix = xprefix;
@@ -397,7 +397,7 @@ static struct jffs2_xattr_datum *create_xattr_datum(struct jffs2_sb_info *c,
 static void delete_xattr_datum(struct jffs2_sb_info *c, struct jffs2_xattr_datum *xd)
 {
         /* must be called under down_write(xattr_sem) */
-        BUG_ON(xd->refcnt);
+        BUG_ON(atomic_read(&xd->refcnt));
 
         unload_xattr_datum(c, xd);
         xd->flags |= JFFS2_XFLAGS_DEAD;
@@ -580,7 +580,7 @@ static void delete_xattr_ref(struct jffs2_sb_info *c, struct jffs2_xattr_ref *re
         dbg_xattr("xref(ino=%u, xid=%u, xseqno=%u) was removed.\n",
                   ref->ino, ref->xid, ref->xseqno);
 
-        if (!--xd->refcnt)
+        if (atomic_dec_and_test(&xd->refcnt))
                 delete_xattr_datum(c, xd);
 }
 
@@ -612,8 +612,7 @@ void jffs2_xattr_free_inode(struct jffs2_sb_info *c, struct jffs2_inode_cache *i
         for (ref = ic->xref; ref; ref = _ref) {
                 _ref = ref->next;
                 xd = ref->xd;
-                xd->refcnt--;
-                if (!xd->refcnt) {
+                if (atomic_dec_and_test(&xd->refcnt)) {
                         unload_xattr_datum(c, xd);
                         jffs2_free_xattr_datum(xd);
                 }
@@ -835,7 +834,7 @@ void jffs2_build_xattr_subsystem(struct jffs2_sb_info *c)
                         }
                         ref->xd = xd;
                         ref->ic = ic;
-                        xd->refcnt++;
+                        atomic_inc(&xd->refcnt);
                         ref->next = ic->xref;
                         ic->xref = ref;
                 }
@@ -846,7 +845,7 @@ void jffs2_build_xattr_subsystem(struct jffs2_sb_info *c)
                 list_for_each_entry_safe(xd, _xd, &c->xattrindex[i], xindex) {
                         xdatum_count++;
                         list_del_init(&xd->xindex);
-                        if (!xd->refcnt) {
+                        if (!atomic_read(&xd->refcnt)) {
                                 dbg_xattr("xdatum(xid=%u, version=%u) is orphan.\n",
                                           xd->xid, xd->version);
                                 xd->flags |= JFFS2_XFLAGS_DEAD;
@@ -1120,7 +1119,7 @@ int do_jffs2_setxattr(struct inode *inode, int xprefix, const char *xname,
                                         ref->next = c->xref_dead_list;
                                         c->xref_dead_list = ref;
                                         spin_unlock(&c->erase_completion_lock);
-                                        if (!--xd->refcnt)
+                                        if (atomic_dec_and_test(&xd->refcnt))
                                                 delete_xattr_datum(c, xd);
                                 } else {
                                         ref->ic = ic;
@@ -1157,8 +1156,7 @@ int do_jffs2_setxattr(struct inode *inode, int xprefix, const char *xname,
         down_write(&c->xattr_sem);
         if (rc) {
                 JFFS2_WARNING("jffs2_reserve_space()=%d, request=%u\n", rc, request);
-                xd->refcnt--;
-                if (!xd->refcnt)
+                if (atomic_dec_and_test(&xd->refcnt))
                         delete_xattr_datum(c, xd);
                 up_write(&c->xattr_sem);
                 return rc;
@@ -1172,8 +1170,7 @@ int do_jffs2_setxattr(struct inode *inode, int xprefix, const char *xname,
                         ic->xref = ref;
                 }
                 rc = PTR_ERR(newref);
-                xd->refcnt--;
-                if (!xd->refcnt)
+                if (atomic_dec_and_test(&xd->refcnt))
                         delete_xattr_datum(c, xd);
         } else if (ref) {
                 delete_xattr_ref(c, ref);
@@ -1304,7 +1301,7 @@ int jffs2_verify_xattr(struct jffs2_sb_info *c)
 void jffs2_release_xattr_datum(struct jffs2_sb_info *c, struct jffs2_xattr_datum *xd)
 {
         /* must be called under spin_lock(&c->erase_completion_lock) */
-        if (xd->refcnt > 0 || xd->node != (void *)xd)
+        if (atomic_read(&xd->refcnt) || xd->node != (void *)xd)
                 return;
 
         list_del(&xd->xindex);
diff --git a/fs/jffs2/xattr.h b/fs/jffs2/xattr.h
index 4a10abc6d917..06a5c69dcf8b 100644
--- a/fs/jffs2/xattr.h
+++ b/fs/jffs2/xattr.h
@@ -28,7 +28,7 @@ struct jffs2_xattr_datum
         uint16_t xprefix;               /* see JFFS2_XATTR_PREFIX_* */
 
         struct list_head xindex;        /* chained from c->xattrindex[n] */
-        uint32_t refcnt;                /* # of xattr_ref refers this */
+        atomic_t refcnt;                /* # of xattr_ref refers this */
         uint32_t xid;
         uint32_t version;