Coda: add spin lock to protect accesses to struct coda_inode_info.

We mostly need it to protect cached user permissions. The c_flags field
is advisory, reading the wrong value is harmless and in the worst case
we hit a slow path where we have to make an extra upcall to the
userspace cache manager when revalidating a dentry or inode.

Signed-off-by: Yoshihisa Abe <yoshiabe@cs.cmu.edu>
Signed-off-by: Jan Harkes <jaharkes@cs.cmu.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 5 deletions

diff --git a/fs/coda/cache.c b/fs/coda/cache.c
index a5bf5771a22a..9060f08e70cf 100644
--- a/fs/coda/cache.c
+++ b/fs/coda/cache.c
@@ -17,6 +17,7 @@
 #include <linux/string.h>
 #include <linux/list.h>
 #include <linux/sched.h>
+#include <linux/spinlock.h>
 
 #include <linux/coda.h>
 #include <linux/coda_linux.h>
@@ -31,19 +32,23 @@ void coda_cache_enter(struct inode *inode, int mask)
 {
         struct coda_inode_info *cii = ITOC(inode);
 
+        spin_lock(&cii->c_lock);
         cii->c_cached_epoch = atomic_read(&permission_epoch);
         if (cii->c_uid != current_fsuid()) {
                 cii->c_uid = current_fsuid();
                 cii->c_cached_perm = mask;
         } else
                 cii->c_cached_perm |= mask;
+        spin_unlock(&cii->c_lock);
 }
 
 /* remove cached acl from an inode */
 void coda_cache_clear_inode(struct inode *inode)
 {
         struct coda_inode_info *cii = ITOC(inode);
+        spin_lock(&cii->c_lock);
         cii->c_cached_epoch = atomic_read(&permission_epoch) - 1;
+        spin_unlock(&cii->c_lock);
 }
 
 /* remove all acl caches */
@@ -57,13 +62,15 @@ void coda_cache_clear_all(struct super_block *sb)
 int coda_cache_check(struct inode *inode, int mask)
 {
         struct coda_inode_info *cii = ITOC(inode);
-        int hit;
+        int hit;
         
-        hit = (mask & cii->c_cached_perm) == mask &&
-                cii->c_uid == current_fsuid() &&
-                cii->c_cached_epoch == atomic_read(&permission_epoch);
+        spin_lock(&cii->c_lock);
+        hit = (mask & cii->c_cached_perm) == mask &&
+            cii->c_uid == current_fsuid() &&
+            cii->c_cached_epoch == atomic_read(&permission_epoch);
+        spin_unlock(&cii->c_lock);
 
-        return hit;
+        return hit;
 }