[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>

diff --git a/fs/jffs2/xattr.c b/fs/jffs2/xattr.c
index 7622f79..18e66db 100644 (file)
--- 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 4a10abc..06a5c69 100644 (file)
--- 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;