[RFC][PATCH 3/3] Coda: replace BKL with mutex

From: Jan Harkes
Date: Wed Oct 20 2010 - 16:24:20 EST

From: Yoshihisa Abe <yoshiabe@xxxxxxxxxx>

Replace the BKL with a mutex to provide atomicity during mounting and to
protect access to the upcall queues in struct venus_comm.

Signed-off-by: Yoshihisa Abe <yoshiabe@xxxxxxxxxx>
Signed-off-by: Jan Harkes <jaharkes@xxxxxxxxxx>
---
fs/coda/inode.c | 44 ++++++++++++++++++++++++++++++--------------
fs/coda/psdev.c | 28 +++++++++++++++++-----------
fs/coda/upcall.c | 13 ++++++++-----
include/linux/coda_psdev.h | 2 ++
4 files changed, 57 insertions(+), 30 deletions(-)

diff --git a/fs/coda/inode.c b/fs/coda/inode.c
index d287bed..3b94b7a 100644
--- a/fs/coda/inode.c
+++ b/fs/coda/inode.c
@@ -15,6 +15,7 @@
#include <linux/stat.h>
#include <linux/errno.h>
#include <linux/unistd.h>
+#include <linux/mutex.h>
#include <linux/spinlock.h>
#include <linux/file.h>
#include <linux/vfs.h>
@@ -144,7 +145,7 @@ static int get_device_index(struct coda_mount_data *data)
static int coda_fill_super(struct super_block *sb, void *data, int silent)
{
struct inode *root = NULL;
- struct venus_comm *vc = NULL;
+ struct venus_comm *vc;
struct CodaFid fid;
int error;
int idx;
@@ -158,21 +159,26 @@ static int coda_fill_super(struct super_block *sb, void *data, int silent)
printk(KERN_INFO "coda_read_super: device index: %i\n", idx);

vc = &coda_comms[idx];
+ mutex_lock(&vc->vc_mutex);
+
if (!vc->vc_inuse) {
printk("coda_read_super: No pseudo device\n");
- return -EINVAL;
+ error = -EINVAL;
+ goto unlock_out;
}

- if ( vc->vc_sb ) {
+ if (vc->vc_sb) {
printk("coda_read_super: Device already mounted\n");
- return -EBUSY;
+ error = -EBUSY;
+ goto unlock_out;
}

error = bdi_setup_and_register(&vc->bdi, "coda", BDI_CAP_MAP_COPY);
if (error)
- goto bdi_err;
+ goto unlock_out;

vc->vc_sb = sb;
+ mutex_unlock(&vc->vc_mutex);

sb->s_fs_info = vc;
sb->s_flags |= MS_NOATIME;
@@ -201,26 +207,36 @@ static int coda_fill_super(struct super_block *sb, void *data, int silent)
printk("coda_read_super: rootinode is %ld dev %s\n",
root->i_ino, root->i_sb->s_id);
sb->s_root = d_alloc_root(root);
- if (!sb->s_root)
+ if (!sb->s_root) {
+ error = -EINVAL;
goto error;
+ }
return 0;

- error:
- bdi_destroy(&vc->bdi);
- bdi_err:
+error:
if (root)
iput(root);
- if (vc)
- vc->vc_sb = NULL;

- return -EINVAL;
+ mutex_lock(&vc->vc_mutex);
+ bdi_destroy(&vc->bdi);
+ vc->vc_sb = NULL;
+ sb->s_fs_info = NULL;
+ mutex_unlock(&vc->vc_mutex);
+ return error;
+
+unlock_out:
+ mutex_unlock(&vc->vc_mutex);
+ return error;
}

static void coda_put_super(struct super_block *sb)
{
- bdi_destroy(&coda_vcp(sb)->bdi);
- coda_vcp(sb)->vc_sb = NULL;
+ struct venus_comm *vcp = coda_vcp(sb);
+ mutex_lock(&vcp->vc_mutex);
+ bdi_destroy(&vcp->bdi);
+ vcp->vc_sb = NULL;
sb->s_fs_info = NULL;
+ mutex_unlock(&vcp->vc_mutex);

printk("Coda: Bye bye.\n");
}
diff --git a/fs/coda/psdev.c b/fs/coda/psdev.c
index f786759..d815c24 100644
--- a/fs/coda/psdev.c
+++ b/fs/coda/psdev.c
@@ -35,7 +35,7 @@
#include <linux/poll.h>
#include <linux/init.h>
#include <linux/list.h>
-#include <linux/smp_lock.h>
+#include <linux/mutex.h>
#include <linux/device.h>
#include <asm/io.h>
#include <asm/system.h>
@@ -67,8 +67,10 @@ static unsigned int coda_psdev_poll(struct file *file, poll_table * wait)
unsigned int mask = POLLOUT | POLLWRNORM;

poll_wait(file, &vcp->vc_waitq, wait);
+ mutex_lock(&vcp->vc_mutex);
if (!list_empty(&vcp->vc_pending))
mask |= POLLIN | POLLRDNORM;
+ mutex_unlock(&vcp->vc_mutex);

return mask;
}
@@ -150,7 +152,7 @@ static ssize_t coda_psdev_write(struct file *file, const char __user *buf,
}

/* Look for the message on the processing queue. */
- lock_kernel();
+ mutex_lock(&vcp->vc_mutex);
list_for_each(lh, &vcp->vc_processing) {
tmp = list_entry(lh, struct upc_req , uc_chain);
if (tmp->uc_unique == hdr.unique) {
@@ -159,7 +161,7 @@ static ssize_t coda_psdev_write(struct file *file, const char __user *buf,
break;
}
}
- unlock_kernel();
+ mutex_unlock(&vcp->vc_mutex);

if (!req) {
printk("psdev_write: msg (%d, %d) not found\n",
@@ -214,7 +216,7 @@ static ssize_t coda_psdev_read(struct file * file, char __user * buf,
if (nbytes == 0)
return 0;

- lock_kernel();
+ mutex_lock(&vcp->vc_mutex);

add_wait_queue(&vcp->vc_waitq, &wait);
set_current_state(TASK_INTERRUPTIBLE);
@@ -228,7 +230,9 @@ static ssize_t coda_psdev_read(struct file * file, char __user * buf,
retval = -ERESTARTSYS;
break;
}
+ mutex_unlock(&vcp->vc_mutex);
schedule();
+ mutex_lock(&vcp->vc_mutex);
}

set_current_state(TASK_RUNNING);
@@ -261,7 +265,7 @@ static ssize_t coda_psdev_read(struct file * file, char __user * buf,
CODA_FREE(req->uc_data, sizeof(struct coda_in_hdr));
kfree(req);
out:
- unlock_kernel();
+ mutex_unlock(&vcp->vc_mutex);
return (count ? count : retval);
}

@@ -274,10 +278,10 @@ static int coda_psdev_open(struct inode * inode, struct file * file)
if (idx < 0 || idx >= MAX_CODADEVS)
return -ENODEV;

- lock_kernel();
-
err = -EBUSY;
vcp = &coda_comms[idx];
+ mutex_lock(&vcp->vc_mutex);
+
if (!vcp->vc_inuse) {
vcp->vc_inuse++;

@@ -291,7 +295,7 @@ static int coda_psdev_open(struct inode * inode, struct file * file)
err = 0;
}

- unlock_kernel();
+ mutex_unlock(&vcp->vc_mutex);
return err;
}

@@ -306,7 +310,7 @@ static int coda_psdev_release(struct inode * inode, struct file * file)
return -1;
}

- lock_kernel();
+ mutex_lock(&vcp->vc_mutex);

/* Wakeup clients so they can return. */
list_for_each_entry_safe(req, tmp, &vcp->vc_pending, uc_chain) {
@@ -331,7 +335,7 @@ static int coda_psdev_release(struct inode * inode, struct file * file)

file->private_data = NULL;
vcp->vc_inuse--;
- unlock_kernel();
+ mutex_unlock(&vcp->vc_mutex);
return 0;
}

@@ -359,9 +363,11 @@ static int init_coda_psdev(void)
err = PTR_ERR(coda_psdev_class);
goto out_chrdev;
}
- for (i = 0; i < MAX_CODADEVS; i++)
+ for (i = 0; i < MAX_CODADEVS; i++) {
+ mutex_init(&(&coda_comms[i])->vc_mutex);
device_create(coda_psdev_class, NULL,
MKDEV(CODA_PSDEV_MAJOR, i), NULL, "cfs%d", i);
+ }
coda_sysctl_init();
goto out;

diff --git a/fs/coda/upcall.c b/fs/coda/upcall.c
index e53847f..e41b906 100644
--- a/fs/coda/upcall.c
+++ b/fs/coda/upcall.c
@@ -27,7 +27,7 @@
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/slab.h>
-#include <linux/smp_lock.h>
+#include <linux/mutex.h>
#include <asm/uaccess.h>
#include <linux/vmalloc.h>
#include <linux/vfs.h>
@@ -607,7 +607,8 @@ static void coda_unblock_signals(sigset_t *old)
(r)->uc_opcode != CODA_RELEASE) || \
(r)->uc_flags & CODA_REQ_READ))

-static inline void coda_waitfor_upcall(struct upc_req *req)
+static inline void coda_waitfor_upcall(struct venus_comm *vcp,
+ struct upc_req *req)
{
DECLARE_WAITQUEUE(wait, current);
unsigned long timeout = jiffies + coda_timeout * HZ;
@@ -640,10 +641,12 @@ static inline void coda_waitfor_upcall(struct upc_req *req)
break;
}

+ mutex_unlock(&vcp->vc_mutex);
if (blocked)
schedule_timeout(HZ);
else
schedule();
+ mutex_lock(&vcp->vc_mutex);
}
if (blocked)
coda_unblock_signals(&old);
@@ -671,7 +674,7 @@ static int coda_upcall(struct venus_comm *vcp,
struct upc_req *req = NULL, *sig_req;
int error;

- lock_kernel();
+ mutex_lock(&vcp->vc_mutex);

if (!vcp->vc_inuse) {
printk(KERN_NOTICE "coda: Venus dead, not sending upcall\n");
@@ -711,7 +714,7 @@ static int coda_upcall(struct venus_comm *vcp,
* ENODEV. */

/* Go to sleep. Wake up on signals only after the timeout. */
- coda_waitfor_upcall(req);
+ coda_waitfor_upcall(vcp, req);

/* Op went through, interrupt or not... */
if (req->uc_flags & CODA_REQ_WRITE) {
@@ -765,7 +768,7 @@ static int coda_upcall(struct venus_comm *vcp,

exit:
kfree(req);
- unlock_kernel();
+ mutex_unlock(&vcp->vc_mutex);
return error;
}

diff --git a/include/linux/coda_psdev.h b/include/linux/coda_psdev.h
index 284b520..42a8229 100644
--- a/include/linux/coda_psdev.h
+++ b/include/linux/coda_psdev.h
@@ -8,6 +8,7 @@

#ifdef __KERNEL__
#include <linux/backing-dev.h>
+#include <linux/mutex.h>

struct kstatfs;

@@ -20,6 +21,7 @@ struct venus_comm {
int vc_inuse;
struct super_block *vc_sb;
struct backing_dev_info bdi;
+ struct mutex vc_mutex;
};


--
1.6.3.3

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