diff options
| -rw-r--r-- | fs/file_table.c | 2 | ||||
| -rw-r--r-- | fs/inode.c | 2 | ||||
| -rw-r--r-- | fs/namespace.c | 40 | ||||
| -rw-r--r-- | fs/open.c | 4 | ||||
| -rw-r--r-- | fs/xattr.c | 4 | ||||
| -rw-r--r-- | include/linux/mount.h | 4 |
6 files changed, 50 insertions, 6 deletions
diff --git a/fs/file_table.c b/fs/file_table.c index 54018fe..3d66dbc 100644 --- a/fs/file_table.c +++ b/fs/file_table.c @@ -214,7 +214,7 @@ int init_file(struct file *file, struct vfsmount *mnt, struct dentry *dentry, */ if ((mode & FMODE_WRITE) && !special_file(dentry->d_inode->i_mode)) { file_take_write(file); - error = mnt_want_write(mnt); + error = mnt_clone_write(mnt); WARN_ON(error); } return error; @@ -1422,7 +1422,7 @@ void file_update_time(struct file *file) if (IS_NOCMTIME(inode)) return; - err = mnt_want_write(file->f_path.mnt); + err = mnt_want_write_file(file); if (err) return; diff --git a/fs/namespace.c b/fs/namespace.c index 22ae06a..120b8a6 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -265,6 +265,46 @@ out: EXPORT_SYMBOL_GPL(mnt_want_write); /** + * mnt_clone_write - get write access to a mount + * @mnt: the mount on which to take a write + * + * This is effectively like mnt_want_write, except + * it must only be used to take an extra write reference + * on a mountpoint that we already know has a write reference + * on it. This allows some optimisation. + * + * After finished, mnt_drop_write must be called as usual to + * drop the reference. + */ +int mnt_clone_write(struct vfsmount *mnt) +{ + /* superblock may be r/o */ + if (__mnt_is_readonly(mnt)) + return -EROFS; + preempt_disable(); + inc_mnt_writers(mnt); + preempt_enable(); + return 0; +} +EXPORT_SYMBOL_GPL(mnt_clone_write); + +/** + * mnt_want_write_file - get write access to a file's mount + * @file: the file who's mount on which to take a write + * + * This is like mnt_want_write, but it takes a file and can + * do some optimisations if the file is open for write already + */ +int mnt_want_write_file(struct file *file) +{ + if (!(file->f_mode & FMODE_WRITE)) + return mnt_want_write(file->f_path.mnt); + else + return mnt_clone_write(file->f_path.mnt); +} +EXPORT_SYMBOL_GPL(mnt_want_write_file); + +/** * mnt_drop_write - give up write access to a mount * @mnt: the mount on which to give up write access * @@ -612,7 +612,7 @@ SYSCALL_DEFINE2(fchmod, unsigned int, fd, mode_t, mode) audit_inode(NULL, dentry); - err = mnt_want_write(file->f_path.mnt); + err = mnt_want_write_file(file); if (err) goto out_putf; mutex_lock(&inode->i_mutex); @@ -761,7 +761,7 @@ SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group) if (!file) goto out; - error = mnt_want_write(file->f_path.mnt); + error = mnt_want_write_file(file); if (error) goto out_fput; dentry = file->f_path.dentry; @@ -297,7 +297,7 @@ SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name, return error; dentry = f->f_path.dentry; audit_inode(NULL, dentry); - error = mnt_want_write(f->f_path.mnt); + error = mnt_want_write_file(f); if (!error) { error = setxattr(dentry, name, value, size, flags); mnt_drop_write(f->f_path.mnt); @@ -524,7 +524,7 @@ SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name) return error; dentry = f->f_path.dentry; audit_inode(NULL, dentry); - error = mnt_want_write(f->f_path.mnt); + error = mnt_want_write_file(f); if (!error) { error = removexattr(dentry, name); mnt_drop_write(f->f_path.mnt); diff --git a/include/linux/mount.h b/include/linux/mount.h index ac49c1f..5d52753 100644 --- a/include/linux/mount.h +++ b/include/linux/mount.h @@ -88,7 +88,11 @@ static inline struct vfsmount *mntget(struct vfsmount *mnt) return mnt; } +struct file; /* forward dec */ + extern int mnt_want_write(struct vfsmount *mnt); +extern int mnt_want_write_file(struct file *file); +extern int mnt_clone_write(struct vfsmount *mnt); extern void mnt_drop_write(struct vfsmount *mnt); extern void mntput_no_expire(struct vfsmount *mnt); extern void mnt_pin(struct vfsmount *mnt); |
