[PATCH] files: break up files struct

In order for the RCU to work, the file table array, sets and their sizes must
be updated atomically.  Instead of ensuring this through too many memory
barriers, we put the arrays and their sizes in a separate structure.  This
patch takes the first step of putting the file table elements in a separate
structure fdtable that is embedded withing files_struct.  It also changes all
the users to refer to the file table using files_fdtable() macro.  Subsequent
applciation of RCU becomes easier after this.

Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 13 insertions, 6 deletions

diff --git a/arch/alpha/kernel/osf_sys.c b/arch/alpha/kernel/osf_sys.c
index 167fd89f8707..2b034182a0ca 100644
--- a/arch/alpha/kernel/osf_sys.c
+++ b/arch/alpha/kernel/osf_sys.c
@@ -974,6 +974,7 @@ osf_select(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp,
         size_t size;
         long timeout;
         int ret = -EINVAL;
+        struct fdtable *fdt;
 
         timeout = MAX_SCHEDULE_TIMEOUT;
         if (tvp) {
@@ -995,7 +996,8 @@ osf_select(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp,
                 }
         }
 
-        if (n < 0 || n > current->files->max_fdset)
+        fdt = files_fdtable(current->files);
+        if (n < 0 || n > fdt->max_fdset)
                 goto out_nofds;
 
         /*
diff --git a/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c
index f1201ac8a116..4ad97b3b39dc 100644
--- a/arch/ia64/kernel/perfmon.c
+++ b/arch/ia64/kernel/perfmon.c
@@ -38,6 +38,7 @@
 #include <linux/pagemap.h>
 #include <linux/mount.h>
 #include <linux/bitops.h>
+#include <linux/rcupdate.h>
 
 #include <asm/errno.h>
 #include <asm/intrinsics.h>
@@ -2217,15 +2218,17 @@ static void
 pfm_free_fd(int fd, struct file *file)
 {
         struct files_struct *files = current->files;
+        struct fdtable *fdt = files_fdtable(files);
 
         /* 
          * there ie no fd_uninstall(), so we do it here
          */
         spin_lock(&files->file_lock);
-        files->fd[fd] = NULL;
+        rcu_assign_pointer(fdt->fd[fd], NULL);
         spin_unlock(&files->file_lock);
 
-        if (file) put_filp(file);
+        if (file)
+                put_filp(file);
         put_unused_fd(fd);
 }
 
diff --git a/arch/sparc64/solaris/ioctl.c b/arch/sparc64/solaris/ioctl.c
index cac0a1cf0050..374766455f5e 100644
--- a/arch/sparc64/solaris/ioctl.c
+++ b/arch/sparc64/solaris/ioctl.c
@@ -293,11 +293,13 @@ static struct module_info {
 static inline int solaris_sockmod(unsigned int fd, unsigned int cmd, u32 arg)
 {
         struct inode *ino;
+        struct fdtable *fdt;
         /* I wonder which of these tests are superfluous... --patrik */
         spin_lock(&current->files->file_lock);
-        if (! current->files->fd[fd] ||
-            ! current->files->fd[fd]->f_dentry ||
-            ! (ino = current->files->fd[fd]->f_dentry->d_inode) ||
+        fdt = files_fdtable(current->files);
+        if (! fdt->fd[fd] ||
+            ! fdt->fd[fd]->f_dentry ||
+            ! (ino = fdt->fd[fd]->f_dentry->d_inode) ||
             ! S_ISSOCK(ino->i_mode)) {
                 spin_unlock(&current->files->file_lock);
                 return TBADF;