[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>

2 files changed, 7 insertions, 2 deletions

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 37668fe998ad..d88d518d30f6 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -159,6 +159,7 @@ static inline char * task_state(struct task_struct *p, char *buffer)
 {
         struct group_info *group_info;
         int g;
+        struct fdtable *fdt = NULL;
 
         read_lock(&tasklist_lock);
         buffer += sprintf(buffer,
@@ -179,10 +180,12 @@ static inline char * task_state(struct task_struct *p, char *buffer)
                 p->gid, p->egid, p->sgid, p->fsgid);
         read_unlock(&tasklist_lock);
         task_lock(p);
+        if (p->files)
+                fdt = files_fdtable(p->files);
         buffer += sprintf(buffer,
                 "FDSize:\t%d\n"
                 "Groups:\t",
-                p->files ? p->files->max_fds : 0);
+                fdt ? fdt->max_fds : 0);
 
         group_info = p->group_info;
         get_group_info(group_info);
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 84751f3f52d5..d0087a0b024b 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1039,6 +1039,7 @@ static int proc_readfd(struct file * filp, void * dirent, filldir_t filldir)
         int retval;
         char buf[NUMBUF];
         struct files_struct * files;
+        struct fdtable *fdt;
 
         retval = -ENOENT;
         if (!pid_alive(p))
@@ -1062,8 +1063,9 @@ static int proc_readfd(struct file * filp, void * dirent, filldir_t filldir)
                         if (!files)
                                 goto out;
                         spin_lock(&files->file_lock);
+                        fdt = files_fdtable(files);
                         for (fd = filp->f_pos-2;
-                             fd < files->max_fds;
+                             fd < fdt->max_fds;
                              fd++, filp->f_pos++) {
                                 unsigned int i,j;