| Message ID | 1437467876-22106-6-git-send-email-yangds.fnst@cn.fujitsu.com |
|---|---|
| State | Superseded |
| Headers | show |
On Tue 21-07-15 16:37:36, Dongsheng Yang wrote: > Function lookup_cdev works similar with lookup_bdev, we can get > a cdev instance by lookup_cdev with a parameter of dev name. > > This function will be used in quotactl to get a cdev by a dev name. > > Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com> > --- > fs/char_dev.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ > include/linux/fs.h | 2 ++ > 2 files changed, 74 insertions(+) Thanks for the patch. ... > +struct cdev *lookup_cdev(const char *pathname) > +{ > + struct cdev *cdev; > + struct inode *inode; > + struct path path; > + int error; > + > + if (!pathname || !*pathname) > + return ERR_PTR(-EINVAL); > + > + error = kern_path(pathname, LOOKUP_FOLLOW, &path); > + if (error) > + return ERR_PTR(error); > + > + inode = d_backing_inode(path.dentry); > + error = -ENODEV; > + if (!S_ISCHR(inode->i_mode)) > + goto fail; > + error = -EACCES; > + if (path.mnt->mnt_flags & MNT_NODEV) > + goto fail; > + error = -ENXIO; > + cdev = cd_acquire(inode); > + if (!cdev) > + goto fail; > +out: > + path_put(&path); > + return cdev; > +fail: > + cdev = ERR_PTR(error); > + goto out; > +} Again I don't like the code duplication here. Can we have a common function lookup_dev() like: int lookup_dev(const char *pathname, struct cdev **cdevp, struct block_device **bdevp) { struct inode *inode; struct path path; int error; if (!pathname || !*pathname) return -EINVAL; error = kern_path(pathname, LOOKUP_FOLLOW, &path); if (error) return error; inode = d_backing_inode(path.dentry); error = -ENODEV; if (!((S_ISCHR(inode->i_mode) && cdevp) || (S_ISBLK(inode->i_mode) && bdevp))) goto out; error = -EACCES; if (path.mnt->mnt_flags & MNT_NODEV) goto out; error = -ENXIO; if (S_ISCHR(inode->i_mode)) { struct cdev *cdev; cdev = cd_acquire(inode); if (!cdev) goto out; *cdevp = cdev; } else { struct block_device *bdev; bdev = bd_acquire(inode); if (!bdev) goto out; *bdevp = bdev; } error = 0; out: path_put(&path); return error; } It is then easy to wrap lookup_bdev() around it. I'm not too happy about the function prototype but I still think it's better than the duplication. Al? Also quota code can then easily use this lookup_dev() function instead of trying one device type and then another one... Honza
diff --git a/fs/char_dev.c b/fs/char_dev.c index ea06a3d..899f08b 100644 --- a/fs/char_dev.c +++ b/fs/char_dev.c @@ -22,6 +22,9 @@ #include <linux/backing-dev.h> #include <linux/tty.h> +#include <linux/namei.h> +#include <linux/mount.h> + #include "internal.h" static struct kobj_map *cdev_map; @@ -439,6 +442,74 @@ static int exact_lock(dev_t dev, void *data) return cdev_get(p) ? 0 : -1; } +static struct cdev *cd_acquire(struct inode *inode) +{ + struct cdev *cdev; + struct cdev *new = NULL; + + spin_lock(&cdev_lock); + cdev = inode->i_cdev; + if (!cdev) { + struct kobject *kobj; + int idx; + spin_unlock(&cdev_lock); + kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx); + if (!kobj) { + cdev = NULL; + goto out; + } + new = container_of(kobj, struct cdev, kobj); + spin_lock(&cdev_lock); + /* Check i_cdev again in case somebody beat us to it while + we dropped the lock. */ + cdev = inode->i_cdev; + if (!cdev) { + inode->i_cdev = cdev = new; + list_add(&inode->i_devices, &cdev->list); + } + } + + if (!cdev_get(cdev)) + cdev = NULL; + spin_unlock(&cdev_lock); + +out: + return cdev; +} + +struct cdev *lookup_cdev(const char *pathname) +{ + struct cdev *cdev; + struct inode *inode; + struct path path; + int error; + + if (!pathname || !*pathname) + return ERR_PTR(-EINVAL); + + error = kern_path(pathname, LOOKUP_FOLLOW, &path); + if (error) + return ERR_PTR(error); + + inode = d_backing_inode(path.dentry); + error = -ENODEV; + if (!S_ISCHR(inode->i_mode)) + goto fail; + error = -EACCES; + if (path.mnt->mnt_flags & MNT_NODEV) + goto fail; + error = -ENXIO; + cdev = cd_acquire(inode); + if (!cdev) + goto fail; +out: + path_put(&path); + return cdev; +fail: + cdev = ERR_PTR(error); + goto out; +} + /** * cdev_add() - add a char device to the system * @p: the cdev structure for the device @@ -561,6 +632,7 @@ void __init chrdev_init(void) EXPORT_SYMBOL(register_chrdev_region); EXPORT_SYMBOL(unregister_chrdev_region); EXPORT_SYMBOL(alloc_chrdev_region); +EXPORT_SYMBOL(lookup_cdev); EXPORT_SYMBOL(cdev_init); EXPORT_SYMBOL(cdev_alloc); EXPORT_SYMBOL(cdev_del); diff --git a/include/linux/fs.h b/include/linux/fs.h index 5c7d789..860b235 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2308,6 +2308,8 @@ extern void __unregister_chrdev(unsigned int major, unsigned int baseminor, unsigned int count, const char *name); extern void unregister_chrdev_region(dev_t, unsigned); extern void chrdev_show(struct seq_file *,off_t); +extern struct cdev *lookup_cdev(const char *); + static inline int register_chrdev(unsigned int major, const char *name, const struct file_operations *fops)
Function lookup_cdev works similar with lookup_bdev, we can get a cdev instance by lookup_cdev with a parameter of dev name. This function will be used in quotactl to get a cdev by a dev name. Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com> --- fs/char_dev.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/fs.h | 2 ++ 2 files changed, 74 insertions(+)