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[PATCH] files: lock-free fd look-up

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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>
This commit is contained in:
Dipankar Sarma
2005-09-09 13:04:14 -07:00
committed by Linus Torvalds
parent ab2af1f500
commit b835996f62
9 changed files with 39 additions and 27 deletions
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29
fs/proc/base.c
View File

@@ -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 @@ static int proc_fd_link(struct inode *inode, struct dentry **dentry, struct vfsm
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 @@ static int proc_readfd(struct file * filp, void * dirent, filldir_t filldir)
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 @@ static int proc_readfd(struct file * filp, void * dirent, filldir_t filldir)
if (!fcheck_files(files, fd))
continue;
spin_unlock(&files->file_lock);
rcu_read_unlock();
j = NUMBUF;
i = fd;
@@ -1083,12 +1084,12 @@ static int proc_readfd(struct file * filp, void * dirent, filldir_t filldir)
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 @@ static int tid_fd_revalidate(struct dentry *dentry, struct nameidata *nd)
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 @@ static int tid_fd_revalidate(struct dentry *dentry, struct nameidata *nd)
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 @@ static struct dentry *proc_lookupfd(struct inode * dir, struct dentry * dentry,
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 @@ static struct dentry *proc_lookupfd(struct inode * dir, struct dentry * dentry,
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 @@ static struct dentry *proc_lookupfd(struct inode * dir, struct dentry * dentry,
return NULL;
out_unlock2:
spin_unlock(&files->file_lock);
rcu_read_unlock();
put_files_struct(files);
out_unlock:
iput(inode);