vfs: Add name to file handle conversion support
in [Kernel]
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From: Miklos Szeredi on 12 Jul 2010 04:20 On Mon, 12 Jul 2010, Aneesh Kumar K.V wrote: > The file handle also include mount id which can be used > to lookup file system specific information such as uuid > in /proc/<pid>mountinfo > > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar(a)linux.vnet.ibm.com> > --- > fs/open.c | 124 ++++++++++++++++++++++++++++++++++++++++++++++ > include/linux/fs.h | 9 +++ > include/linux/syscalls.h | 5 ++- > 3 files changed, 137 insertions(+), 1 deletions(-) > > diff --git a/fs/open.c b/fs/open.c > index 5463266..7ad8f28 100644 > --- a/fs/open.c > +++ b/fs/open.c > @@ -29,6 +29,7 @@ > #include <linux/falloc.h> > #include <linux/fs_struct.h> > #include <linux/ima.h> > +#include <linux/exportfs.h> > > #include "internal.h" > > @@ -1040,3 +1041,126 @@ int nonseekable_open(struct inode *inode, struct file *filp) > } > > EXPORT_SYMBOL(nonseekable_open); > + > +#ifdef CONFIG_EXPORTFS > +/* limit the handle size to some value */ > +#define MAX_HANDLE_SZ 4096 > +static long do_sys_name_to_handle(struct path *path, > + struct file_handle __user *ufh) > +{ > + long retval; > + int handle_size; > + struct file_handle f_handle; > + struct file_handle *handle = NULL; > + > + if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) { > + retval = -EFAULT; > + goto err_out; > + } > + if (f_handle.handle_size > MAX_HANDLE_SZ) { > + retval = -EINVAL; > + goto err_out; > + } > + handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_size, > + GFP_KERNEL); > + if (!handle) { > + retval = -ENOMEM; > + goto err_out; > + } > + > + /* convert handle size to multiple of sizeof(u32) */ > + handle_size = f_handle.handle_size >> 2; > + > + /* we ask for a non connected handle */ > + retval = exportfs_encode_fh(path->dentry, > + (struct fid *)handle->f_handle, > + &handle_size, 0); > + /* convert handle size to bytes */ > + handle_size *= sizeof(u32); > + handle->handle_type = retval; > + handle->handle_size = handle_size; > + /* copy the mount id */ > + handle->mnt_id = path->mnt->mnt_id; > + if (handle_size > f_handle.handle_size) { > + /* > + * set the handle_size to zero so we copy only > + * non variable part of the file_handle > + */ > + handle_size = 0; > + retval = -EOVERFLOW; > + } else > + retval = 0; > + if (copy_to_user(ufh, handle, > + sizeof(struct file_handle) + handle_size)) > + retval = -EFAULT; > + > + kfree(handle); > +err_out: > + return retval; > +} > + > +/** > + * sys_name_to_handle_at: convert name to handle > + * @dfd: directory relative to which name is interpreted if not absolute > + * @name: name that should be converted to handle. > + * @handle: resulting file handle > + * @flag: flag value to indicate whether to follow symlink or not > + * > + * @handle->handle_size indicate the space available to store the > + * variable part of the file handle in bytes. If there is not > + * enough space, the field is updated to return the minimum > + * value required. > + */ > +SYSCALL_DEFINE4(name_to_handle_at, int, dfd, const char __user *, name, > + struct file_handle __user *, handle, int, flag) > +{ > + > + int follow; > + int fput_needed; > + long ret = -EINVAL; > + struct path path, *pp; > + struct file *file = NULL; > + > + if ((flag & ~AT_SYMLINK_FOLLOW) != 0) > + goto err_out; > + > + if (name == NULL && dfd != AT_FDCWD) { > + file = fget_light(dfd, &fput_needed); > + if (file) { > + pp = &file->f_path; > + ret = 0; > + } else > + ret = -EBADF; > + } else { > + follow = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0; > + ret = user_path_at(dfd, name, follow, &path); > + pp = &path; > + } > + if (ret) > + goto err_out; > + /* > + * We need t make sure wether the file system > + * support decoding of the file handle > + */ > + if (!pp->mnt->mnt_sb->s_export_op || > + !pp->mnt->mnt_sb->s_export_op->fh_to_dentry) { > + ret = -EOPNOTSUPP; > + goto out_path; > + } > + ret = do_sys_name_to_handle(pp, handle); > + > +out_path: > + if (file) > + fput_light(file, fput_needed); > + else > + path_put(&path); > +err_out: > + return ret; > +} > +#else > +SYSCALL_DEFINE4(name_to_handle_at, int, dfd, const char __user *, name, > + struct file_handle __user *, handle, int, flag) > +{ > + return -ENOSYS; > +} > +#endif > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 471e1ff..0e7cf4c 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -949,6 +949,15 @@ struct file { > unsigned long f_mnt_write_state; > #endif > }; > + > +struct file_handle { > + int mnt_id; The mount id is not part of the handle in that it's not used when converting back a handle to a file descriptor. So it shouldn't be included here. The uuid can be looked up based on st_dev. > + int handle_size; > + int handle_type; > + /* file identifier */ > + unsigned char f_handle[0]; > +}; > + > extern spinlock_t files_lock; > #define file_list_lock() spin_lock(&files_lock); > #define file_list_unlock() spin_unlock(&files_lock); > diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h > index 7f614ce..9d6d6e3 100644 > --- a/include/linux/syscalls.h > +++ b/include/linux/syscalls.h > @@ -61,6 +61,7 @@ struct robust_list_head; > struct getcpu_cache; > struct old_linux_dirent; > struct perf_event_attr; > +struct file_handle; > > #include <linux/types.h> > #include <linux/aio_abi.h> > @@ -823,5 +824,7 @@ asmlinkage long sys_mmap_pgoff(unsigned long addr, unsigned long len, > unsigned long prot, unsigned long flags, > unsigned long fd, unsigned long pgoff); > asmlinkage long sys_old_mmap(struct mmap_arg_struct __user *arg); > - > +asmlinkage long sys_name_to_handle_at(int dfd, const char __user *name, > + struct file_handle __user *handle, > + int flag); > #endif > -- > 1.7.2.rc1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo(a)vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Aneesh Kumar K. V on 12 Jul 2010 05:40 On Mon, 12 Jul 2010 10:15:29 +0200, Miklos Szeredi <miklos(a)szeredi.hu> wrote: > On Mon, 12 Jul 2010, Aneesh Kumar K.V wrote: > > The file handle also include mount id which can be used > > to lookup file system specific information such as uuid > > in /proc/<pid>mountinfo > > > > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar(a)linux.vnet.ibm.com> > > --- > > fs/open.c | 124 ++++++++++++++++++++++++++++++++++++++++++++++ > > include/linux/fs.h | 9 +++ > > include/linux/syscalls.h | 5 ++- > > 3 files changed, 137 insertions(+), 1 deletions(-) > > > > diff --git a/fs/open.c b/fs/open.c > > index 5463266..7ad8f28 100644 > > --- a/fs/open.c > > +++ b/fs/open.c > > @@ -29,6 +29,7 @@ > > #include <linux/falloc.h> > > #include <linux/fs_struct.h> > > #include <linux/ima.h> > > +#include <linux/exportfs.h> > > > > #include "internal.h" > > > > @@ -1040,3 +1041,126 @@ int nonseekable_open(struct inode *inode, struct file *filp) > > } > > > > EXPORT_SYMBOL(nonseekable_open); > > + > > +#ifdef CONFIG_EXPORTFS > > +/* limit the handle size to some value */ > > +#define MAX_HANDLE_SZ 4096 > > +static long do_sys_name_to_handle(struct path *path, > > + struct file_handle __user *ufh) > > +{ > > + long retval; > > + int handle_size; > > + struct file_handle f_handle; > > + struct file_handle *handle = NULL; > > + > > + if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) { > > + retval = -EFAULT; > > + goto err_out; > > + } > > + if (f_handle.handle_size > MAX_HANDLE_SZ) { > > + retval = -EINVAL; > > + goto err_out; > > + } > > + handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_size, > > + GFP_KERNEL); > > + if (!handle) { > > + retval = -ENOMEM; > > + goto err_out; > > + } > > + > > + /* convert handle size to multiple of sizeof(u32) */ > > + handle_size = f_handle.handle_size >> 2; > > + > > + /* we ask for a non connected handle */ > > + retval = exportfs_encode_fh(path->dentry, > > + (struct fid *)handle->f_handle, > > + &handle_size, 0); > > + /* convert handle size to bytes */ > > + handle_size *= sizeof(u32); > > + handle->handle_type = retval; > > + handle->handle_size = handle_size; > > + /* copy the mount id */ > > + handle->mnt_id = path->mnt->mnt_id; > > + if (handle_size > f_handle.handle_size) { > > + /* > > + * set the handle_size to zero so we copy only > > + * non variable part of the file_handle > > + */ > > + handle_size = 0; > > + retval = -EOVERFLOW; > > + } else > > + retval = 0; > > + if (copy_to_user(ufh, handle, > > + sizeof(struct file_handle) + handle_size)) > > + retval = -EFAULT; > > + > > + kfree(handle); > > +err_out: > > + return retval; > > +} > > + > > +/** > > + * sys_name_to_handle_at: convert name to handle > > + * @dfd: directory relative to which name is interpreted if not absolute > > + * @name: name that should be converted to handle. > > + * @handle: resulting file handle > > + * @flag: flag value to indicate whether to follow symlink or not > > + * > > + * @handle->handle_size indicate the space available to store the > > + * variable part of the file handle in bytes. If there is not > > + * enough space, the field is updated to return the minimum > > + * value required. > > + */ > > +SYSCALL_DEFINE4(name_to_handle_at, int, dfd, const char __user *, name, > > + struct file_handle __user *, handle, int, flag) > > +{ > > + > > + int follow; > > + int fput_needed; > > + long ret = -EINVAL; > > + struct path path, *pp; > > + struct file *file = NULL; > > + > > + if ((flag & ~AT_SYMLINK_FOLLOW) != 0) > > + goto err_out; > > + > > + if (name == NULL && dfd != AT_FDCWD) { > > + file = fget_light(dfd, &fput_needed); > > + if (file) { > > + pp = &file->f_path; > > + ret = 0; > > + } else > > + ret = -EBADF; > > + } else { > > + follow = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0; > > + ret = user_path_at(dfd, name, follow, &path); > > + pp = &path; > > + } > > + if (ret) > > + goto err_out; > > + /* > > + * We need t make sure wether the file system > > + * support decoding of the file handle > > + */ > > + if (!pp->mnt->mnt_sb->s_export_op || > > + !pp->mnt->mnt_sb->s_export_op->fh_to_dentry) { > > + ret = -EOPNOTSUPP; > > + goto out_path; > > + } > > + ret = do_sys_name_to_handle(pp, handle); > > + > > +out_path: > > + if (file) > > + fput_light(file, fput_needed); > > + else > > + path_put(&path); > > +err_out: > > + return ret; > > +} > > +#else > > +SYSCALL_DEFINE4(name_to_handle_at, int, dfd, const char __user *, name, > > + struct file_handle __user *, handle, int, flag) > > +{ > > + return -ENOSYS; > > +} > > +#endif > > diff --git a/include/linux/fs.h b/include/linux/fs.h > > index 471e1ff..0e7cf4c 100644 > > --- a/include/linux/fs.h > > +++ b/include/linux/fs.h > > @@ -949,6 +949,15 @@ struct file { > > unsigned long f_mnt_write_state; > > #endif > > }; > > + > > +struct file_handle { > > + int mnt_id; > > The mount id is not part of the handle in that it's not used when > converting back a handle to a file descriptor. So it shouldn't be > included here. > > The uuid can be looked up based on st_dev. > That would include another stat call on the file to get the st_dev ? As per the last review (Message-id:20100708082143.3701bfc7(a)notabene.brown) http://article.gmane.org/gmane.linux.kernel/1007385 we discussed that it would be nice to add st_dev as a part of handle. Later I suggested it would be nice to get mount_id instead of st_dev because st_dev is not stable (against remounts) for file system that doesn't have a backing device. So instead of using something that is partially stable, add mnt_id which is explicitly stated to be unstable across remounts. If you are against having mount_id as a part of struct file_handle, do you think we could add it as a extra argument to syscall ? -aneesh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Miklos Szeredi on 12 Jul 2010 12:40 On Mon, 12 Jul 2010, Aneesh Kumar K. V wrote: > That would include another stat call on the file to get the st_dev ? As > per the last review (Message-id:20100708082143.3701bfc7(a)notabene.brown) > http://article.gmane.org/gmane.linux.kernel/1007385 we discussed that > it would be nice to add st_dev as a part of handle. Later I suggested > it would be nice to get mount_id instead of st_dev because st_dev is > not stable (against remounts) for file system that doesn't have a > backing device. So instead of using something that is partially stable, > add mnt_id which is explicitly stated to be unstable across remounts. > > If you are against having mount_id as a part of struct file_handle, do > you think we could add it as a extra argument to syscall ? Yeah, I think that would be cleaner. Thanks, Miklos -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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