[PATCH V12 09/12] famfs: Register secondary daxdevs by path (FAMFSIOC_DAXDEV_OPEN)

From: John Groves <[email protected]>=0D=0A=0D=0AFamfs file maps (fmaps) ma=
y reference multiple daxdevs. Before passing=0D=0Aan fmap that references=
 a new daxdev, the daxdev is pushed into the=0D=0Akernel via FAMFSIOC_DAX=
DEV_OPEN). This adds daxdevs to daxdev_table for=0D=0Aindex-based resolut=
ion from famfs extents to daxdevs.=0D=0A=0D=0ASigned-off-by: John Groves =
<[email protected]>=0D=0A---=0D=0A fs/famfs/famfs_file.c            | 74 ++=
++++++++++++++++++++++++++++++=0D=0A include/uapi/linux/famfs_ioctl.h | 2=
4 +++++++++++=0D=0A 2 files changed, 98 insertions(+)=0D=0A=0D=0Adiff --g=
it a/fs/famfs/famfs_file.c b/fs/famfs/famfs_file.c=0D=0Aindex e7f271ce6d0=
3..e11a55ecf8d7 100644=0D=0A--- a/fs/famfs/famfs_file.c=0D=0A+++ b/fs/fam=
fs/famfs_file.c=0D=0A@@ -287,6 +287,76 @@ famfs_file_init_dax(struct file=
 *file, void __user *arg)=0D=0A =09return rc;=0D=0A }=0D=0A=20=0D=0A+/**=0D=
=0A+ * famfs_daxdev_open() - FAMFSIOC_DAXDEV_OPEN ioctl handler=0D=0A+ * =
@file: any file in the famfs mount (the table is per-superblock)=0D=0A+ *=
 @arg:  ptr to struct famfs_ioc_daxdev in user space=0D=0A+ *=0D=0A+ * Re=
gister a devdax device (identified by path) into the mount's daxdev table=
=0D=0A+ * at the caller-specified index, so files whose extents reference=
 that index=0D=0A+ * can be mapped. The path is resolved by lookup_daxdev=
() - the same helper the=0D=0A+ * mount uses for the primary daxdev - so =
every slot is resolved identically.=0D=0A+ * Registering exposes raw devi=
ce memory, so it requires CAP_SYS_RAWIO.=0D=0A+ */=0D=0A+static int=0D=0A=
+famfs_daxdev_open(struct file *file, void __user *arg)=0D=0A+{=0D=0A+=09=
struct super_block *sb =3D file_inode(file)->i_sb;=0D=0A+=09struct famfs_=
fs_info *fsi =3D sb->s_fs_info;=0D=0A+=09struct famfs_ioc_daxdev dd;=0D=0A=
+=09dev_t devno;=0D=0A+=09char *path;=0D=0A+=09int rc;=0D=0A+=0D=0A+=09if=
 (!capable(CAP_SYS_RAWIO))=0D=0A+=09=09return -EPERM;=0D=0A+=0D=0A+=09if =
(copy_from_user(&dd, arg, sizeof(dd)))=0D=0A+=09=09return -EFAULT;=0D=0A+=
=0D=0A+=09/* @flags is reserved; reject non-zero so it stays available */=
=0D=0A+=09if (dd.flags)=0D=0A+=09=09return -EINVAL;=0D=0A+=0D=0A+=09/*=0D=
=0A+=09 * If this daxdev index is already populated there is nothing to d=
o.=0D=0A+=09 * The index is cluster-invariant, so a valid slot already na=
mes this=0D=0A+=09 * device; skip the path resolution entirely. install_d=
axdev() rechecks=0D=0A+=09 * ->valid under the write lock, so this is pur=
ely an optimization.=0D=0A+=09 */=0D=0A+=09scoped_guard(rwsem_read, &fsi-=
>devlist_sem) {=0D=0A+=09=09if (dd.daxdev_index >=3D fsi->dax_devlist->ns=
lots)=0D=0A+=09=09=09return -EINVAL;=0D=0A+=09=09if (fsi->dax_devlist->de=
vlist[dd.daxdev_index].valid)=0D=0A+=09=09=09return 0;=0D=0A+=09}=0D=0A+=0D=
=0A+=09if (dd.daxdev_path_len =3D=3D 0 || dd.daxdev_path_len >=3D PATH_MA=
X)=0D=0A+=09=09return -EINVAL;=0D=0A+=0D=0A+=09/* +1 so the terminating N=
UL is included within the bound */=0D=0A+=09path =3D strndup_user((const =
char __user *)(uintptr_t)dd.daxdev_path,=0D=0A+=09=09=09    dd.daxdev_pat=
h_len + 1);=0D=0A+=09if (IS_ERR(path))=0D=0A+=09=09return PTR_ERR(path);=0D=
=0A+=0D=0A+=09rc =3D lookup_daxdev(path, &devno);=0D=0A+=09if (rc)=0D=0A+=
=09=09goto out;=0D=0A+=0D=0A+=09/*=0D=0A+=09 * The daxdev table is alloca=
ted at mount time (for the slot-0 primary),=0D=0A+=09 * so it is always p=
resent here; no need to allocate it.=0D=0A+=09 */=0D=0A+=09rc =3D famfs_i=
nstall_daxdev(fsi, sb, dd.daxdev_index, devno, path);=0D=0A+=09if (rc)=0D=
=0A+=09=09pr_debug("%s: failed to install daxdev index %llu (%s)\n",=0D=0A=
+=09=09       __func__, dd.daxdev_index, path);=0D=0A+out:=0D=0A+=09kfree=
(path);=0D=0A+=09return rc;=0D=0A+}=0D=0A+=0D=0A /**=0D=0A  * famfs_file_=
ioctl() - Top-level famfs file ioctl handler=0D=0A  * @file: the file=0D=0A=
@@ -308,6 +378,10 @@ famfs_file_ioctl(struct file *file, unsigned int cmd=
, unsigned long arg)=0D=0A =09=09rc =3D 0;=0D=0A =09=09break;=0D=0A=20=0D=
=0A+=09case FAMFSIOC_DAXDEV_OPEN:=0D=0A+=09=09rc =3D famfs_daxdev_open(fi=
le, (void __user *)arg);=0D=0A+=09=09break;=0D=0A+=0D=0A =09case FAMFSIOC=
_MAP_CREATE:=0D=0A =09=09rc =3D famfs_file_init_dax(file, (void __user *)=
arg);=0D=0A =09=09break;=0D=0Adiff --git a/include/uapi/linux/famfs_ioctl=
=2Eh b/include/uapi/linux/famfs_ioctl.h=0D=0Aindex b4eb373c1ade..751d8b03=
3c2e 100644=0D=0A--- a/include/uapi/linux/famfs_ioctl.h=0D=0A+++ b/includ=
e/uapi/linux/famfs_ioctl.h=0D=0A@@ -77,6 +77,29 @@ struct famfs_ioc_fmap_=
header {=0D=0A =09__u64 reserved1;=0D=0A };=0D=0A=20=0D=0A+/**=0D=0A+ * s=
truct famfs_ioc_daxdev - register an additional backing daxdev by path=0D=
=0A+ * @daxdev_index:    the (cluster-invariant) index this daxdev occupi=
es in=0D=0A+ *                   extent dev_index fields. Index 0 is the =
mount-time primary.=0D=0A+ * @daxdev_path:     userspace pointer to the d=
evdax device path (e.g.=0D=0A+ *                   "/dev/dax0.0"); resolv=
ed in the kernel the same way the=0D=0A+ *                   mount primar=
y is.=0D=0A+ * @daxdev_path_len: length of the path string, not counting =
the NUL.=0D=0A+ * @flags:           reserved; must be zero.=0D=0A+ *=0D=0A=
+ * Standalone famfs registers every daxdev by path: the mount primary co=
mes in=0D=0A+ * as the mount device name, and slots 1..n come in here. (T=
his deliberately=0D=0A+ * differs from fuse's fd-based FUSE_DEV_IOC_DAXDE=
V_OPEN; each side is uniform=0D=0A+ * within itself.) Passing the path by=
 pointer keeps the struct fixed-size, so=0D=0A+ * longer paths never requ=
ire an ABI change.=0D=0A+ */=0D=0A+struct famfs_ioc_daxdev {=0D=0A+=09__u=
64 daxdev_index;=0D=0A+=09__u64 daxdev_path;=0D=0A+=09__u32 daxdev_path_l=
en;=0D=0A+=09__u32 flags;=0D=0A+};=0D=0A+=0D=0A #define FAMFSIOC_MAGIC 'u=
'=0D=0A=20=0D=0A /* famfs file ioctl opcodes */=0D=0A@@ -87,5 +110,6 @@ s=
truct famfs_ioc_fmap_header {=0D=0A  * famfs_ioc_fmap_header followed by =
the extent list (see above).=0D=0A  */=0D=0A #define FAMFSIOC_MAP_CREATE =
   _IOW(FAMFSIOC_MAGIC,  0x51, struct famfs_ioc_fmap_header)=0D=0A+#defin=
e FAMFSIOC_DAXDEV_OPEN   _IOW(FAMFSIOC_MAGIC,  0x52, struct famfs_ioc_dax=
dev)=0D=0A=20=0D=0A #endif /* FAMFS_IOCTL_H */=0D=0A--=20=0D=0A2.53.0=0D=0A=
=0D=0A