[PATCH] files: lock-free fd look-up
With the use of RCU in files structure, the look-up of files using fds can now
be lock-free. The lookup is protected by rcu_read_lock()/rcu_read_unlock().
This patch changes the readers to use lock-free lookup.
Signed-off-by: Maneesh Soni <maneesh@in.ibm.com>
Signed-off-by: Ravikiran Thirumalai <kiran_th@gmail.com>
Signed-off-by: Dipankar Sarma <dipankar@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/proc/base.c b/fs/proc/base.c
index d0087a0..23db452 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -62,6 +62,7 @@
#include <linux/namespace.h>
#include <linux/mm.h>
#include <linux/smp_lock.h>
+#include <linux/rcupdate.h>
#include <linux/kallsyms.h>
#include <linux/mount.h>
#include <linux/security.h>
@@ -283,16 +284,16 @@
files = get_files_struct(task);
if (files) {
- spin_lock(&files->file_lock);
+ rcu_read_lock();
file = fcheck_files(files, fd);
if (file) {
*mnt = mntget(file->f_vfsmnt);
*dentry = dget(file->f_dentry);
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();
put_files_struct(files);
return 0;
}
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();
put_files_struct(files);
}
return -ENOENT;
@@ -1062,7 +1063,7 @@
files = get_files_struct(p);
if (!files)
goto out;
- spin_lock(&files->file_lock);
+ rcu_read_lock();
fdt = files_fdtable(files);
for (fd = filp->f_pos-2;
fd < fdt->max_fds;
@@ -1071,7 +1072,7 @@
if (!fcheck_files(files, fd))
continue;
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();
j = NUMBUF;
i = fd;
@@ -1083,12 +1084,12 @@
ino = fake_ino(tid, PROC_TID_FD_DIR + fd);
if (filldir(dirent, buf+j, NUMBUF-j, fd+2, ino, DT_LNK) < 0) {
- spin_lock(&files->file_lock);
+ rcu_read_lock();
break;
}
- spin_lock(&files->file_lock);
+ rcu_read_lock();
}
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();
put_files_struct(files);
}
out:
@@ -1263,9 +1264,9 @@
files = get_files_struct(task);
if (files) {
- spin_lock(&files->file_lock);
+ rcu_read_lock();
if (fcheck_files(files, fd)) {
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();
put_files_struct(files);
if (task_dumpable(task)) {
inode->i_uid = task->euid;
@@ -1277,7 +1278,7 @@
security_task_to_inode(task, inode);
return 1;
}
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();
put_files_struct(files);
}
d_drop(dentry);
@@ -1369,7 +1370,7 @@
if (!files)
goto out_unlock;
inode->i_mode = S_IFLNK;
- spin_lock(&files->file_lock);
+ rcu_read_lock();
file = fcheck_files(files, fd);
if (!file)
goto out_unlock2;
@@ -1377,7 +1378,7 @@
inode->i_mode |= S_IRUSR | S_IXUSR;
if (file->f_mode & 2)
inode->i_mode |= S_IWUSR | S_IXUSR;
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();
put_files_struct(files);
inode->i_op = &proc_pid_link_inode_operations;
inode->i_size = 64;
@@ -1387,7 +1388,7 @@
return NULL;
out_unlock2:
- spin_unlock(&files->file_lock);
+ rcu_read_unlock();
put_files_struct(files);
out_unlock:
iput(inode);
