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consolidate the reassignments of ->f_op in ->open() instances 

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2013-09-22 14:17:15 -04:00
parent 7b00ed6fe6
commit e84f9e57b9
8 changed files with 43 additions and 77 deletions
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12
drivers/char/misc.c
View File

@ -114,7 +114,7 @@ static int misc_open(struct inode * inode, struct file * file)
int minor = iminor(inode);
struct miscdevice *c;
int err = -ENODEV;
const struct file_operations *old_fops, *new_fops = NULL;
const struct file_operations *new_fops = NULL;
mutex_lock(&misc_mtx);
@ -141,17 +141,11 @@ static int misc_open(struct inode * inode, struct file * file)
}
err = 0;
old_fops = file->f_op;
file->f_op = new_fops;
replace_fops(file, new_fops);
if (file->f_op->open) {
file->private_data = c;
err=file->f_op->open(inode,file);
if (err) {
fops_put(file->f_op);
file->f_op = fops_get(old_fops);
}
err = file->f_op->open(inode,file);
}
fops_put(old_fops);
fail:
mutex_unlock(&misc_mtx);
return err;

17
drivers/gpu/drm/drm_fops.c
View File

@ -148,7 +148,7 @@ int drm_stub_open(struct inode *inode, struct file *filp)
struct drm_minor *minor;
int minor_id = iminor(inode);
int err = -ENODEV;
const struct file_operations *old_fops;
const struct file_operations *new_fops;
DRM_DEBUG("\n");
@ -163,18 +163,13 @@ int drm_stub_open(struct inode *inode, struct file *filp)
if (drm_device_is_unplugged(dev))
goto out;
old_fops = filp->f_op;
filp->f_op = fops_get(dev->driver->fops);
if (filp->f_op == NULL) {
filp->f_op = old_fops;
new_fops = fops_get(dev->driver->fops);
if (!new_fops)
goto out;
}
if (filp->f_op->open && (err = filp->f_op->open(inode, filp))) {
fops_put(filp->f_op);
filp->f_op = fops_get(old_fops);
}
fops_put(old_fops);
replace_fops(filp, new_fops);
if (filp->f_op->open)
err = filp->f_op->open(inode, filp);
out:
mutex_unlock(&drm_global_mutex);
return err;

19
drivers/media/dvb-core/dvbdev.c
View File

@ -74,22 +74,15 @@ static int dvb_device_open(struct inode *inode, struct file *file)
if (dvbdev && dvbdev->fops) {
int err = 0;
const struct file_operations *old_fops;
const struct file_operations *new_fops;
file->private_data = dvbdev;
old_fops = file->f_op;
file->f_op = fops_get(dvbdev->fops);
if (file->f_op == NULL) {
file->f_op = old_fops;
new_fops = fops_get(dvbdev->fops);
if (!new_fops)
goto fail;
}
if(file->f_op->open)
file->private_data = dvbdev;
replace_fops(file, new_fops);
if (file->f_op->open)
err = file->f_op->open(inode,file);
if (err) {
fops_put(file->f_op);
file->f_op = fops_get(old_fops);
}
fops_put(old_fops);
up_read(&minor_rwsem);
mutex_unlock(&dvbdev_mutex);
return err;

16
drivers/usb/core/file.c
View File

@ -29,27 +29,19 @@ static DECLARE_RWSEM(minor_rwsem);
static int usb_open(struct inode * inode, struct file * file)
{
int minor = iminor(inode);
const struct file_operations *c;
int err = -ENODEV;
const struct file_operations *old_fops, *new_fops = NULL;
const struct file_operations *new_fops;
down_read(&minor_rwsem);
c = usb_minors[minor];
new_fops = fops_get(usb_minors[iminor(inode)]);
if (!c || !(new_fops = fops_get(c)))
if (!new_fops)
goto done;
old_fops = file->f_op;
file->f_op = new_fops;
replace_fops(file, new_fops);
/* Curiouser and curiouser... NULL ->open() as "no device" ? */
if (file->f_op->open)
err = file->f_op->open(inode,file);
if (err) {
fops_put(file->f_op);
file->f_op = fops_get(old_fops);
}
fops_put(old_fops);
done:
up_read(&minor_rwsem);
return err;

6
fs/char_dev.c
View File

@ -368,6 +368,7 @@ void cdev_put(struct cdev *p)
*/
static int chrdev_open(struct inode *inode, struct file *filp)
{
const struct file_operations *fops;
struct cdev *p;
struct cdev *new = NULL;
int ret = 0;
@ -400,10 +401,11 @@ static int chrdev_open(struct inode *inode, struct file *filp)
return ret;
ret = -ENXIO;
filp->f_op = fops_get(p->ops);
if (!filp->f_op)
fops = fops_get(p->ops);
if (!fops)
goto out_cdev_put;
replace_fops(filp, fops);
if (filp->f_op->open) {
ret = filp->f_op->open(inode, filp);
if (ret)

11
include/linux/fs.h
View File

@ -1875,6 +1875,17 @@ extern struct dentry *mount_pseudo(struct file_system_type *, char *,
(((fops) && try_module_get((fops)->owner) ? (fops) : NULL))
#define fops_put(fops) \
do { if (fops) module_put((fops)->owner); } while(0)
/*
* This one is to be used *ONLY* from ->open() instances.
* fops must be non-NULL, pinned down *and* module dependencies
* should be sufficient to pin the caller down as well.
*/
#define replace_fops(f, fops) \
do { \
struct file *__file = (f); \
fops_put(__file->f_op); \
BUG_ON(!(__file->f_op = (fops))); \
} while(0)
extern int register_filesystem(struct file_system_type *);
extern int unregister_filesystem(struct file_system_type *);

22
sound/core/sound.c
View File

@ -153,7 +153,7 @@ static int snd_open(struct inode *inode, struct file *file)
{
unsigned int minor = iminor(inode);
struct snd_minor *mptr = NULL;
const struct file_operations *old_fops;
const struct file_operations *new_fops;
int err = 0;
if (minor >= ARRAY_SIZE(snd_minors))
@ -167,24 +167,14 @@ static int snd_open(struct inode *inode, struct file *file)
return -ENODEV;
}
}
old_fops = file->f_op;
file->f_op = fops_get(mptr->f_ops);
if (file->f_op == NULL) {
file->f_op = old_fops;
err = -ENODEV;
}
new_fops = fops_get(mptr->f_ops);
mutex_unlock(&sound_mutex);
if (err < 0)
return err;
if (!new_fops)
return -ENODEV;
replace_fops(file, new_fops);
if (file->f_op->open) {
if (file->f_op->open)
err = file->f_op->open(inode, file);
if (err) {
fops_put(file->f_op);
file->f_op = fops_get(old_fops);
}
}
fops_put(old_fops);
return err;
}

17
sound/sound_core.c
View File

@ -626,31 +626,20 @@ static int soundcore_open(struct inode *inode, struct file *file)
if (s)
new_fops = fops_get(s->unit_fops);
}
spin_unlock(&sound_loader_lock);
if (new_fops) {
/*
* We rely upon the fact that we can't be unloaded while the
* subdriver is there, so if ->open() is successful we can
* safely drop the reference counter and if it is not we can
* revert to old ->f_op. Ugly, indeed, but that's the cost of
* switching ->f_op in the first place.
* subdriver is there.
*/
int err = 0;
const struct file_operations *old_fops = file->f_op;
file->f_op = new_fops;
spin_unlock(&sound_loader_lock);
replace_fops(file, new_fops);
if (file->f_op->open)
err = file->f_op->open(inode,file);
if (err) {
fops_put(file->f_op);
file->f_op = fops_get(old_fops);
}
fops_put(old_fops);
return err;
}
spin_unlock(&sound_loader_lock);
return -ENODEV;
}