minix/servers/vfs/dmap.c
Ben Gras 565f13088f make vfs & filesystems use failable copying
Change the kernel to add features to vircopy and safecopies so that
transparent copy fixing won't happen to avoid deadlocks, and such copies
fail with EFAULT.

Transparently making copying work from filesystems (as normally done by
the kernel & VM when copying fails because of missing/readonly memory)
is problematic as it can happen that, for file-mapped ranges, that that
same filesystem that is blocked on the copy request is needed to satisfy
the memory range, leading to deadlock. Dito for VFS itself, if done with
a blocking call.

This change makes the copying done from a filesystem fail in such cases
with EFAULT by VFS adding the CPF_TRY flag to the grants. If a FS call
fails with EFAULT, VFS will then request the range to be made available
to VM after the FS is unblocked, allowing it to be used to satisfy the
range if need be in another VFS thread.

Similarly, for datacopies that VFS itself does, it uses the failable
vircopy variant and callers use a wrapper that talk to VM if necessary
to get the copy to work.

	. kernel: add CPF_TRY flag to safecopies
	. kernel: only request writable ranges to VM for the
	  target buffer when copying fails
	. do copying in VFS TRY-first
	. some fixes in VM to build SANITYCHECK mode
	. add regression test for the cases where
	  - a FS system call needs memory mapped in a process that the
	    FS itself must map.
	  - such a range covers more than one file-mapped region.
	. add 'try' mode to vircopy, physcopy
	. add flags field to copy kernel call messages
	. if CP_FLAG_TRY is set, do not transparently try
	  to fix memory ranges
	. for use by VFS when accessing user buffers to avoid
	  deadlock
	. remove some obsolete backwards compatability assignments
        . VFS: let thread scheduling work for VM requests too
          Allows VFS to make calls to VM while suspending and resuming
          the currently running thread. Does currently not work for the
          main thread.
        . VM: add fix memory range call for use by VFS

Change-Id: I295794269cea51a3163519a9cfe5901301d90b32
2014-07-28 17:05:14 +02:00

313 lines
9.2 KiB
C

/* This file contains the table with device <-> driver mappings. It also
* contains some routines to dynamically add and/ or remove device drivers
* or change mappings.
*/
#include "fs.h"
#include <assert.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>
#include <unistd.h>
#include <minix/callnr.h>
#include <minix/ds.h>
/* The order of the entries in the table determines the mapping between major
* device numbers and device drivers. Character and block devices
* can be intermixed at random. The ordering determines the device numbers in
* /dev. Note that the major device numbers used in /dev are NOT the same as
* the process numbers of the device drivers. See <minix/dmap.h> for mappings.
*/
struct dmap dmap[NR_DEVICES];
/*===========================================================================*
* lock_dmap *
*===========================================================================*/
void lock_dmap(struct dmap *dp)
{
/* Lock a driver */
struct worker_thread *org_self;
int r;
assert(dp != NULL);
assert(dp->dmap_driver != NONE);
org_self = worker_suspend();
if ((r = mutex_lock(&dp->dmap_lock)) != 0)
panic("unable to get a lock on dmap: %d\n", r);
worker_resume(org_self);
}
/*===========================================================================*
* unlock_dmap *
*===========================================================================*/
void unlock_dmap(struct dmap *dp)
{
/* Unlock a driver */
int r;
assert(dp != NULL);
if ((r = mutex_unlock(&dp->dmap_lock)) != 0)
panic("unable to unlock dmap lock: %d\n", r);
}
/*===========================================================================*
* map_driver *
*===========================================================================*/
static int map_driver(const char label[LABEL_MAX], devmajor_t major,
endpoint_t proc_nr_e)
{
/* Add a new device driver mapping in the dmap table. If the proc_nr is set to
* NONE, we're supposed to unmap it.
*/
size_t len;
struct dmap *dp;
/* Get pointer to device entry in the dmap table. */
if (major < 0 || major >= NR_DEVICES) return(ENODEV);
dp = &dmap[major];
/* Check if we're supposed to unmap it. */
if (proc_nr_e == NONE) {
/* Even when a driver is now unmapped and is shortly to be mapped in
* due to recovery, invalidate associated filps if they're character
* special files. More sophisticated recovery mechanisms which would
* reduce the need to invalidate files are possible, but would require
* cooperation of the driver and more recovery framework between RS,
* VFS, and DS.
*/
invalidate_filp_by_char_major(major);
dp->dmap_driver = NONE;
return(OK);
}
if (label != NULL) {
len = strlen(label);
if (len+1 > sizeof(dp->dmap_label)) {
printf("VFS: map_driver: label too long: %d\n", len);
return(EINVAL);
}
strlcpy(dp->dmap_label, label, sizeof(dp->dmap_label));
}
/* Store driver I/O routines based on type of device */
dp->dmap_driver = proc_nr_e;
return(OK);
}
/*===========================================================================*
* do_mapdriver *
*===========================================================================*/
int do_mapdriver(void)
{
/* Create a device->driver mapping. RS will tell us which major is driven by
* this driver, what type of device it is (regular, TTY, asynchronous, clone,
* etc), and its label. This label is registered with DS, and allows us to
* retrieve the driver's endpoint.
*/
int r, major, slot;
endpoint_t endpoint;
vir_bytes label_vir;
size_t label_len;
char label[LABEL_MAX];
struct fproc *rfp;
/* Only RS can map drivers. */
if (who_e != RS_PROC_NR) return(EPERM);
label_vir = (vir_bytes) job_m_in.VFS_MAPDRIVER_LABEL;
label_len = (size_t) job_m_in.VFS_MAPDRIVER_LABELLEN;
major = job_m_in.VFS_MAPDRIVER_MAJOR;
/* Get the label */
if (label_len > sizeof(label)) { /* Can we store this label? */
printf("VFS: do_mapdriver: label too long\n");
return(EINVAL);
}
r = sys_vircopy(who_e, label_vir, SELF, (vir_bytes) label, label_len,
CP_FLAG_TRY);
if (r != OK) {
printf("VFS: do_mapdriver: sys_vircopy failed: %d\n", r);
return(EINVAL);
}
if (label[label_len-1] != '\0') {
printf("VFS: do_mapdriver: label not null-terminated\n");
return(EINVAL);
}
/* Now we know how the driver is called, fetch its endpoint */
r = ds_retrieve_label_endpt(label, &endpoint);
if (r != OK) {
printf("VFS: do_mapdriver: label '%s' unknown\n", label);
return(EINVAL);
}
/* Process is a service */
if (isokendpt(endpoint, &slot) != OK) {
printf("VFS: can't map driver to unknown endpoint %d\n", endpoint);
return(EINVAL);
}
rfp = &fproc[slot];
rfp->fp_flags |= FP_SRV_PROC;
/* Try to update device mapping. */
return map_driver(label, major, endpoint);
}
/*===========================================================================*
* dmap_unmap_by_endpt *
*===========================================================================*/
void dmap_unmap_by_endpt(endpoint_t proc_e)
{
/* Lookup driver in dmap table by endpoint and unmap it */
int major, r;
for (major = 0; major < NR_DEVICES; major++) {
if (dmap_driver_match(proc_e, major)) {
/* Found driver; overwrite it with a NULL entry */
if ((r = map_driver(NULL, major, NONE)) != OK) {
printf("VFS: unmapping driver %d for major %d failed:"
" %d\n", proc_e, major, r);
}
}
}
}
/*===========================================================================*
* map_service *
*===========================================================================*/
int map_service(struct rprocpub *rpub)
{
/* Map a new service by storing its device driver properties. */
int r, slot;
struct fproc *rfp;
if (IS_RPUB_BOOT_USR(rpub)) return(OK);
/* Process is a service */
if (isokendpt(rpub->endpoint, &slot) != OK) {
printf("VFS: can't map service with unknown endpoint %d\n",
rpub->endpoint);
return(EINVAL);
}
rfp = &fproc[slot];
rfp->fp_flags |= FP_SRV_PROC;
/* Not a driver, nothing more to do. */
if (rpub->dev_nr == NO_DEV) return(OK);
/* Map driver. */
r = map_driver(rpub->label, rpub->dev_nr, rpub->endpoint);
if(r != OK) return(r);
return(OK);
}
/*===========================================================================*
* init_dmap *
*===========================================================================*/
void init_dmap(void)
{
/* Initialize the device mapping table. */
int i;
memset(dmap, 0, sizeof(dmap));
for (i = 0; i < NR_DEVICES; i++) {
dmap[i].dmap_driver = NONE;
dmap[i].dmap_servicing = INVALID_THREAD;
if (mutex_init(&dmap[i].dmap_lock, NULL) != 0)
panic("unable to initialize dmap lock");
}
/* CTTY_MAJOR is a special case, which is handled by VFS itself. */
if (map_driver("vfs", CTTY_MAJOR, CTTY_ENDPT) != OK)
panic("map_driver(CTTY_MAJOR) failed");
}
/*===========================================================================*
* dmap_driver_match *
*===========================================================================*/
int dmap_driver_match(endpoint_t proc, int major)
{
if (major < 0 || major >= NR_DEVICES) return(0);
if (dmap[major].dmap_driver != NONE && dmap[major].dmap_driver == proc)
return(1);
return(0);
}
/*===========================================================================*
* dmap_by_major *
*===========================================================================*/
struct dmap *
get_dmap_by_major(int major)
{
if (major < 0 || major >= NR_DEVICES) return(NULL);
if (dmap[major].dmap_driver == NONE) return(NULL);
return(&dmap[major]);
}
/*===========================================================================*
* dmap_endpt_up *
*===========================================================================*/
void dmap_endpt_up(endpoint_t proc_e, int is_blk)
{
/* A device driver with endpoint proc_e has been restarted. Go tell everyone
* that might be blocking on it that this device is 'up'.
*/
int major;
struct dmap *dp;
struct worker_thread *worker;
if (proc_e == NONE) return;
for (major = 0; major < NR_DEVICES; major++) {
if ((dp = get_dmap_by_major(major)) == NULL) continue;
if (dp->dmap_driver == proc_e) {
if (is_blk) {
if (dp->dmap_recovering) {
printf("VFS: driver recovery failure for"
" major %d\n", major);
if (dp->dmap_servicing != INVALID_THREAD) {
worker = worker_get(dp->dmap_servicing);
worker_stop(worker);
}
dp->dmap_recovering = 0;
continue;
}
dp->dmap_recovering = 1;
bdev_up(major);
dp->dmap_recovering = 0;
} else {
if (dp->dmap_servicing != INVALID_THREAD) {
worker = worker_get(dp->dmap_servicing);
worker_stop(worker);
}
invalidate_filp_by_char_major(major);
}
}
}
}
/*===========================================================================*
* get_dmap *
*===========================================================================*/
struct dmap *get_dmap(endpoint_t proc_e)
{
/* See if 'proc_e' endpoint belongs to a valid dmap entry. If so, return a
* pointer */
int major;
for (major = 0; major < NR_DEVICES; major++)
if (dmap_driver_match(proc_e, major))
return(&dmap[major]);
return(NULL);
}