[PATCH] Coda updates [2/5]

Use a global 'epoch' counter to invalidate cached permissions instead of
traversing a racy linked list of all known Coda inodes.

fs/coda/cache.c

@@ -23,11 +23,14 @@
 #include <linux/coda_fs_i.h>
 #include <linux/coda_cache.h>
 
+static atomic_t permission_epoch = ATOMIC_INIT(0);
+
 /* replace or extend an acl cache hit */
 void coda_cache_enter(struct inode *inode, int mask)
 {
 	struct coda_inode_info *cii = ITOC(inode);
 
+	cii->c_cached_epoch = atomic_read(&permission_epoch);
         if ( !coda_cred_ok(&cii->c_cached_cred) ) {
                 coda_load_creds(&cii->c_cached_cred);
                 cii->c_cached_perm = mask;
@@ -42,22 +45,15 @@ void coda_cache_clear_inode(struct inode *inode)
         cii->c_cached_perm = 0;
 }
 
-/* remove all acl caches for a principal (or all principals when cred == NULL)*/
-void coda_cache_clear_all(struct super_block *sb, struct coda_cred *cred)
+/* remove all acl caches */
+void coda_cache_clear_all(struct super_block *sb)
 {
         struct coda_sb_info *sbi;
-        struct coda_inode_info *cii;
-        struct list_head *tmp;
 
         sbi = coda_sbp(sb);
         if (!sbi) BUG();
 
-        list_for_each(tmp, &sbi->sbi_cihead)
-        {
-		cii = list_entry(tmp, struct coda_inode_info, c_cilist);
-                if (!cred || coda_cred_eq(cred, &cii->c_cached_cred))
-                        cii->c_cached_perm = 0;
-	}
+	atomic_inc(&permission_epoch);
 }
 
 
@@ -67,8 +63,9 @@ int coda_cache_check(struct inode *inode, int mask)
 	struct coda_inode_info *cii = ITOC(inode);
         int hit;
 	
-        hit = ((mask & cii->c_cached_perm) == mask) &&
-                coda_cred_ok(&cii->c_cached_cred);
+        hit = (mask & cii->c_cached_perm) == mask &&
+	    coda_cred_ok(&cii->c_cached_cred) &&
+	    cii->c_cached_epoch == atomic_read(&permission_epoch);
 
         return hit;
 }

fs/coda/cnode.c

@@ -64,7 +64,6 @@ struct inode * coda_iget(struct super_block * sb, ViceFid * fid,
 {
 	struct inode *inode;
 	struct coda_inode_info *cii;
-	struct coda_sb_info *sbi = coda_sbp(sb);
 	unsigned long hash = coda_f2i(fid);
 
 	inode = iget5_locked(sb, hash, coda_test_inode, coda_set_inode, fid);
@@ -77,7 +76,6 @@ struct inode * coda_iget(struct super_block * sb, ViceFid * fid,
 		/* we still need to set i_ino for things like stat(2) */
 		inode->i_ino = hash;
 		cii->c_mapcount = 0;
-		list_add(&cii->c_cilist, &sbi->sbi_cihead);
 		unlock_new_inode(inode);
 	}
 

fs/coda/inode.c

@@ -46,7 +46,6 @@ static struct inode *coda_alloc_inode(struct super_block *sb)
 		return NULL;
 	memset(&ei->c_fid, 0, sizeof(struct ViceFid));
 	ei->c_flags = 0;
-	INIT_LIST_HEAD(&ei->c_cilist);
 	memset(&ei->c_cached_cred, 0, sizeof(struct coda_cred));
 	ei->c_cached_perm = 0;
 	return &ei->vfs_inode;
@@ -170,7 +169,6 @@ static int coda_fill_super(struct super_block *sb, void *data, int silent)
 	vc->vc_sb = sb;
 
 	sbi->sbi_vcomm = vc;
-	INIT_LIST_HEAD(&sbi->sbi_cihead);
 
         sb->s_fs_info = sbi;
         sb->s_blocksize = 1024;	/* XXXXX  what do we put here?? */
@@ -217,7 +215,6 @@ static void coda_put_super(struct super_block *sb)
 
 	sbi = coda_sbp(sb);
 	sbi->sbi_vcomm->vc_sb = NULL;
-        list_del_init(&sbi->sbi_cihead);
 
 	printk("Coda: Bye bye.\n");
 	kfree(sbi);
@@ -225,9 +222,6 @@ static void coda_put_super(struct super_block *sb)
 
 static void coda_clear_inode(struct inode *inode)
 {
-	struct coda_inode_info *cii = ITOC(inode);
-
-	list_del_init(&cii->c_cilist);
 	coda_cache_clear_inode(inode);
 }
 

fs/coda/upcall.c

@@ -819,19 +819,14 @@ int coda_downcall(int opcode, union outputArgs * out, struct super_block *sb)
 	  switch (opcode) {
 
 	  case CODA_FLUSH : {
-		   coda_cache_clear_all(sb, NULL);
+		   coda_cache_clear_all(sb);
 		   shrink_dcache_sb(sb);
 		   coda_flag_inode(sb->s_root->d_inode, C_FLUSH);
 		   return(0);
 	  }
 
 	  case CODA_PURGEUSER : {
-	           struct coda_cred *cred = &out->coda_purgeuser.cred;
-		   if ( !cred ) {
-		           printk("PURGEUSER: null cred!\n");
-			   return 0;
-		   }
-		   coda_cache_clear_all(sb, cred);
+		   coda_cache_clear_all(sb);
 		   return(0);
 	  }
 

include/linux/coda_cache.h

@@ -13,7 +13,7 @@
 /* credential cache */
 void coda_cache_enter(struct inode *inode, int mask);
 void coda_cache_clear_inode(struct inode *);
-void coda_cache_clear_all(struct super_block *sb, struct coda_cred *cred);
+void coda_cache_clear_all(struct super_block *sb);
 int coda_cache_check(struct inode *inode, int mask);
 
 /* for downcalls and attributes and lookups */

include/linux/coda_fs_i.h

@@ -21,6 +21,7 @@ struct coda_inode_info {
         u_short	           c_flags;     /* flags (see below) */
 	struct list_head   c_cilist;    /* list of all coda inodes */
 	unsigned int	   c_mapcount;  /* nr of times this inode is mapped */
+	unsigned int	   c_cached_epoch;
         struct coda_cred   c_cached_cred; /* credentials of cached perms */
         unsigned int       c_cached_perm; /* cached access permissions */
 	struct inode	   vfs_inode;

include/linux/coda_psdev.h

@@ -11,7 +11,6 @@ struct kstatfs;
 struct coda_sb_info
 {
 	struct venus_comm *sbi_vcomm;
-	struct list_head    sbi_cihead;
 };
 
 /* communication pending/processing queues */