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, 10 insertions, 2 deletions

diff --git a/fs/coda/file.c b/fs/coda/file.c
index ad3cd2abeeb4..c4e395781d41 100644
--- a/fs/coda/file.c
+++ b/fs/coda/file.c
@@ -16,6 +16,7 @@
 #include <linux/cred.h>
 #include <linux/errno.h>
 #include <linux/smp_lock.h>
+#include <linux/spinlock.h>
 #include <linux/string.h>
 #include <linux/slab.h>
 #include <asm/uaccess.h>
@@ -109,19 +110,24 @@ coda_file_mmap(struct file *coda_file, struct vm_area_struct *vma)
 
         coda_inode = coda_file->f_path.dentry->d_inode;
         host_inode = host_file->f_path.dentry->d_inode;
+
+        cii = ITOC(coda_inode);
+        spin_lock(&cii->c_lock);
         coda_file->f_mapping = host_file->f_mapping;
         if (coda_inode->i_mapping == &coda_inode->i_data)
                 coda_inode->i_mapping = host_inode->i_mapping;
 
         /* only allow additional mmaps as long as userspace isn't changing
          * the container file on us! */
-        else if (coda_inode->i_mapping != host_inode->i_mapping)
+        else if (coda_inode->i_mapping != host_inode->i_mapping) {
+                spin_unlock(&cii->c_lock);
                 return -EBUSY;
+        }
 
         /* keep track of how often the coda_inode/host_file has been mmapped */
-        cii = ITOC(coda_inode);
         cii->c_mapcount++;
         cfi->cfi_mapcount++;
+        spin_unlock(&cii->c_lock);
 
         return host_file->f_op->mmap(host_file, vma);
 }
@@ -185,11 +191,13 @@ int coda_release(struct inode *coda_inode, struct file *coda_file)
         cii = ITOC(coda_inode);
 
         /* did we mmap this file? */
+        spin_lock(&cii->c_lock);
         if (coda_inode->i_mapping == &host_inode->i_data) {
                 cii->c_mapcount -= cfi->cfi_mapcount;
                 if (!cii->c_mapcount)
                         coda_inode->i_mapping = &coda_inode->i_data;
         }
+        spin_unlock(&cii->c_lock);
 
         fput(cfi->cfi_container);
         kfree(coda_file->private_data);