[PATCH linux-next] jffs2: reduce stack usage in jffs2_build_xattr_subsystem()

[Fabian Frederick]

Use kcalloc() for allocation/flush of 128 pointers table to
reduce stack usage.

Function now returns -ENOMEM or 0 on success.

stackusage
Before:
./fs/jffs2/xattr.c:775  jffs2_build_xattr_subsystem     1208
dynamic,bounded

After:
./fs/jffs2/xattr.c:775  jffs2_build_xattr_subsystem     192
dynamic,bounded

Also update definition when CONFIG_JFFS2_FS_XATTR is not enabled

Tested with an MTD mount point and some user set/getfattr.

Signed-off-by: Fabian Frederick <f...@skynet.be>
---
 fs/jffs2/build.c |  5 ++++-
 fs/jffs2/xattr.c | 14 ++++++++++----
 fs/jffs2/xattr.h |  4 ++--
 3 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/fs/jffs2/build.c b/fs/jffs2/build.c
index b288c8a..f88e0bf 100644
--- a/fs/jffs2/build.c
+++ b/fs/jffs2/build.c
@@ -211,7 +211,10 @@ static int jffs2_build_filesystem(struct jffs2_sb_info *c)
                ic->scan_dents = NULL;
                cond_resched();
        }
-       jffs2_build_xattr_subsystem(c);
+       ret = jffs2_build_xattr_subsystem(c);
+       if (ret)
+               goto exit;
+
        c->flags &= ~JFFS2_SB_FLAG_BUILDING;
 
        dbg_fsbuild("FS build complete\n");
diff --git a/fs/jffs2/xattr.c b/fs/jffs2/xattr.c
index da3e185..95c0496 100644
--- a/fs/jffs2/xattr.c
+++ b/fs/jffs2/xattr.c
@@ -772,10 +772,10 @@ void jffs2_clear_xattr_subsystem(struct jffs2_sb_info *c)
 }
 
 #define XREF_TMPHASH_SIZE      (128)
-void jffs2_build_xattr_subsystem(struct jffs2_sb_info *c)
+int jffs2_build_xattr_subsystem(struct jffs2_sb_info *c)
 {
        struct jffs2_xattr_ref *ref, *_ref;
-       struct jffs2_xattr_ref *xref_tmphash[XREF_TMPHASH_SIZE];
+       struct jffs2_xattr_ref **xref_tmphash;
        struct jffs2_xattr_datum *xd, *_xd;
        struct jffs2_inode_cache *ic;
        struct jffs2_raw_node_ref *raw;
@@ -784,9 +784,13 @@ void jffs2_build_xattr_subsystem(struct jffs2_sb_info *c)
 
        BUG_ON(!(c->flags & JFFS2_SB_FLAG_BUILDING));
 
+
+       xref_tmphash = kcalloc(XREF_TMPHASH_SIZE,
+                              sizeof(struct jffs2_xattr_ref *), GFP_KERNEL);
+       if (!xref_tmphash)
+               return -ENOMEM;
+
        /* Phase.1 : Merge same xref */
-       for (i=0; i < XREF_TMPHASH_SIZE; i++)
-               xref_tmphash[i] = NULL;
        for (ref=c->xref_temp; ref; ref=_ref) {
                struct jffs2_xattr_ref *tmp;
 
@@ -884,6 +888,8 @@ void jffs2_build_xattr_subsystem(struct jffs2_sb_info *c)
                     "%u of xref (%u dead, %u orphan) found.\n",
                     xdatum_count, xdatum_unchecked_count, xdatum_orphan_count,
                     xref_count, xref_dead_count, xref_orphan_count);
+       kfree(xref_tmphash);
+       return 0;
 }
 
 struct jffs2_xattr_datum *jffs2_setup_xattr_datum(struct jffs2_sb_info *c,
diff --git a/fs/jffs2/xattr.h b/fs/jffs2/xattr.h
index 720007b..1b5030a 100644
--- a/fs/jffs2/xattr.h
+++ b/fs/jffs2/xattr.h
@@ -71,7 +71,7 @@ static inline int is_xattr_ref_dead(struct jffs2_xattr_ref 
*ref)
 #ifdef CONFIG_JFFS2_FS_XATTR
 
 extern void jffs2_init_xattr_subsystem(struct jffs2_sb_info *c);
-extern void jffs2_build_xattr_subsystem(struct jffs2_sb_info *c);
+extern int jffs2_build_xattr_subsystem(struct jffs2_sb_info *c);
 extern void jffs2_clear_xattr_subsystem(struct jffs2_sb_info *c);
 
 extern struct jffs2_xattr_datum *jffs2_setup_xattr_datum(struct jffs2_sb_info 
*c,
@@ -103,7 +103,7 @@ extern ssize_t jffs2_listxattr(struct dentry *, char *, 
size_t);
 #else
 
 #define jffs2_init_xattr_subsystem(c)
-#define jffs2_build_xattr_subsystem(c)
+#define jffs2_build_xattr_subsystem(c)         (0)
 #define jffs2_clear_xattr_subsystem(c)
 
 #define jffs2_xattr_do_crccheck_inode(c, ic)
-- 
2.9.3