sanchayanmaity/minix
1
0
Fork 0
Code Issues Pull requests Packages Projects Releases Wiki Activity
minix/servers/vfs/stadir.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

447 lines
13 KiB
C
Raw Blame History

/* This file contains the code for performing four system calls relating to
* status and directories.
*
* The entry points into this file are
* do_chdir: perform the CHDIR system call
* do_chroot: perform the CHROOT system call
* do_lstat: perform the LSTAT system call
* do_stat: perform the STAT system call
* do_fstat: perform the FSTAT system call
* do_statvfs: perform the STATVFS1 system call
* do_fstatvfs: perform the FSTATVFS1 system call
* do_getvfsstat: perform the GETVFSSTAT system call
*/
#include "fs.h"
#include <sys/stat.h>
#include <minix/com.h>
#include <minix/u64.h>
#include <string.h>
#include "file.h"
#include "path.h"
#include <minix/vfsif.h>
#include <minix/callnr.h>
#include "vnode.h"
#include "vmnt.h"
static int change_into(struct vnode **iip, struct vnode *vp);
/*===========================================================================*
* do_fchdir *
*===========================================================================*/
int do_fchdir(void)
{
/* Change directory on already-opened fd. */
struct filp *rfilp;
int r, rfd;
rfd = job_m_in.VFS_FCHDIR_FD;
/* Is the file descriptor valid? */
if ((rfilp = get_filp(rfd, VNODE_READ)) == NULL) return(err_code);
r = change_into(&fp->fp_wd, rfilp->filp_vno);
unlock_filp(rfilp);
return(r);
}
/*===========================================================================*
* do_chdir *
*===========================================================================*/
int do_chdir(void)
{
/* Perform the chdir(name) system call.
* syscall might provide 'name' embedded in the message.
*/
int r;
struct vnode *vp;
struct vmnt *vmp;
char fullpath[PATH_MAX];
struct lookup resolve;
if (copy_path(fullpath, sizeof(fullpath)) != OK)
return(err_code);
/* Try to open the directory */
lookup_init(&resolve, fullpath, PATH_NOFLAGS, &vmp, &vp);
resolve.l_vmnt_lock = VMNT_READ;
resolve.l_vnode_lock = VNODE_READ;
if ((vp = eat_path(&resolve, fp)) == NULL) return(err_code);
r = change_into(&fp->fp_wd, vp);
unlock_vnode(vp);
unlock_vmnt(vmp);
put_vnode(vp);
return(r);
}
/*===========================================================================*
* do_chroot *
*===========================================================================*/
int do_chroot(void)
{
/* Perform the chroot(name) system call.
* syscall might provide 'name' embedded in the message.
*/
int r;
struct vnode *vp;
struct vmnt *vmp;
char fullpath[PATH_MAX];
struct lookup resolve;
if (!super_user) return(EPERM); /* only su may chroot() */
if (copy_path(fullpath, sizeof(fullpath)) != OK)
return(err_code);
/* Try to open the directory */
lookup_init(&resolve, fullpath, PATH_NOFLAGS, &vmp, &vp);
resolve.l_vmnt_lock = VMNT_READ;
resolve.l_vnode_lock = VNODE_READ;
if ((vp = eat_path(&resolve, fp)) == NULL) return(err_code);
r = change_into(&fp->fp_rd, vp);
unlock_vnode(vp);
unlock_vmnt(vmp);
put_vnode(vp);
return(r);
}
/*===========================================================================*
* change_into *
*===========================================================================*/
static int change_into(struct vnode **result, struct vnode *vp)
{
int r;
if (*result == vp) return(OK); /* Nothing to do */
/* It must be a directory and also be searchable */
if (!S_ISDIR(vp->v_mode))
r = ENOTDIR;
else
r = forbidden(fp, vp, X_BIT); /* Check if dir is searchable*/
if (r != OK) return(r);
/* Everything is OK. Make the change. */
put_vnode(*result); /* release the old directory */
dup_vnode(vp);
*result = vp; /* acquire the new one */
return(OK);
}
/*===========================================================================*
* do_stat *
*===========================================================================*/
int do_stat(void)
{
/* Perform the stat(name, buf) system call. */
int r;
struct vnode *vp;
struct vmnt *vmp;
char fullpath[PATH_MAX];
struct lookup resolve;
vir_bytes vname1, statbuf;
size_t vname1_length;
vname1 = (vir_bytes) job_m_in.VFS_STAT_NAME;
vname1_length = (size_t) job_m_in.VFS_STAT_LEN;
statbuf = (vir_bytes) job_m_in.VFS_STAT_BUF;
lookup_init(&resolve, fullpath, PATH_NOFLAGS, &vmp, &vp);
resolve.l_vmnt_lock = VMNT_READ;
resolve.l_vnode_lock = VNODE_READ;
if (fetch_name(vname1, vname1_length, fullpath) != OK) return(err_code);
if ((vp = eat_path(&resolve, fp)) == NULL) return(err_code);
r = req_stat(vp->v_fs_e, vp->v_inode_nr, who_e, statbuf);
unlock_vnode(vp);
unlock_vmnt(vmp);
put_vnode(vp);
return r;
}
/*===========================================================================*
* do_fstat *
*===========================================================================*/
int do_fstat(void)
{
/* Perform the fstat(fd, buf) system call. */
register struct filp *rfilp;
int r, rfd;
vir_bytes statbuf;
statbuf = (vir_bytes) job_m_in.VFS_FSTAT_BUF;
rfd = job_m_in.VFS_FSTAT_FD;
/* Is the file descriptor valid? */
if ((rfilp = get_filp(rfd, VNODE_READ)) == NULL) return(err_code);
r = req_stat(rfilp->filp_vno->v_fs_e, rfilp->filp_vno->v_inode_nr,
who_e, statbuf);
unlock_filp(rfilp);
return(r);
}
/*===========================================================================*
* update_statvfs *
*===========================================================================*/
int update_statvfs(struct vmnt *vmp, struct statvfs *buf)
{
/* Get statistics from a file system, and cache part of the results. */
int r;
if ((r = req_statvfs(vmp->m_fs_e, buf)) != OK)
return r;
vmp->m_stats.f_flag = buf->f_flag;
vmp->m_stats.f_bsize = buf->f_bsize;
vmp->m_stats.f_frsize = buf->f_frsize;
vmp->m_stats.f_iosize = buf->f_iosize;
vmp->m_stats.f_blocks = buf->f_blocks;
vmp->m_stats.f_bfree = buf->f_bfree;
vmp->m_stats.f_bavail = buf->f_bavail;
vmp->m_stats.f_bresvd = buf->f_bresvd;
vmp->m_stats.f_files = buf->f_files;
vmp->m_stats.f_ffree = buf->f_ffree;
vmp->m_stats.f_favail = buf->f_favail;
vmp->m_stats.f_fresvd = buf->f_fresvd;
vmp->m_stats.f_syncreads = buf->f_syncreads;
vmp->m_stats.f_syncwrites = buf->f_syncwrites;
vmp->m_stats.f_asyncreads = buf->f_asyncreads;
vmp->m_stats.f_asyncwrites = buf->f_asyncwrites;
vmp->m_stats.f_namemax = buf->f_namemax;
return OK;
}
/*===========================================================================*
* fill_statvfs *
*===========================================================================*/
static int fill_statvfs(struct vmnt *vmp, endpoint_t endpt, vir_bytes buf_addr,
int flags)
{
/* Fill a statvfs structure in a userspace process. First let the target file
* server fill in most fields, or use the cached copy if ST_NOWAIT is given.
* Then fill in some remaining fields with local information. Finally, copy
* the result to user space.
*/
struct statvfs buf;
if (!(flags & ST_NOWAIT)) {
/* Get fresh statistics from the file system. */
if (update_statvfs(vmp, &buf) != OK)
return EIO;
} else {
/* Use the cached statistics. */
memset(&buf, 0, sizeof(buf));
buf.f_flag = vmp->m_stats.f_flag;
buf.f_bsize = vmp->m_stats.f_bsize;
buf.f_frsize = vmp->m_stats.f_frsize;
buf.f_iosize = vmp->m_stats.f_iosize;
buf.f_blocks = vmp->m_stats.f_blocks;
buf.f_bfree = vmp->m_stats.f_bfree;
buf.f_bavail = vmp->m_stats.f_bavail;
buf.f_bresvd = vmp->m_stats.f_bresvd;
buf.f_files = vmp->m_stats.f_files;
buf.f_ffree = vmp->m_stats.f_ffree;
buf.f_favail = vmp->m_stats.f_favail;
buf.f_fresvd = vmp->m_stats.f_fresvd;
buf.f_syncreads = vmp->m_stats.f_syncreads;
buf.f_syncwrites = vmp->m_stats.f_syncwrites;
buf.f_asyncreads = vmp->m_stats.f_asyncreads;
buf.f_asyncwrites = vmp->m_stats.f_asyncwrites;
buf.f_namemax = vmp->m_stats.f_namemax;
}
if (vmp->m_flags & VMNT_READONLY)
buf.f_flag |= ST_RDONLY;
buf.f_fsid = (unsigned long)vmp->m_dev;
buf.f_fsidx.__fsid_val[0] = (long)vmp->m_dev; /* This is what is done on NetBSD */
buf.f_fsidx.__fsid_val[1] = 0; /* Here they convert the FS type name into a number. */
strlcpy(buf.f_fstypename, vmp->m_fstype, sizeof(buf.f_fstypename));
strlcpy(buf.f_mntonname, vmp->m_mount_path, sizeof(buf.f_mntonname));
strlcpy(buf.f_mntfromname, vmp->m_mount_dev, sizeof(buf.f_mntfromname));
return sys_datacopy_wrapper(SELF, (vir_bytes) &buf,
endpt, buf_addr, sizeof(buf));
}
/*===========================================================================*
* do_statvfs *
*===========================================================================*/
int do_statvfs(void)
{
/* Perform the statvfs1(name, buf, flags) system call. */
int r, flags;
struct vnode *vp;
struct vmnt *vmp;
char fullpath[PATH_MAX];
struct lookup resolve;
vir_bytes vname1, statbuf;
size_t vname1_length;
vname1 = (vir_bytes) job_m_in.VFS_STATVFS1_NAME;
vname1_length = (size_t) job_m_in.VFS_STATVFS1_LEN;
statbuf = (vir_bytes) job_m_in.VFS_STATVFS1_BUF;
flags = job_m_in.VFS_STATVFS1_FLAGS;
lookup_init(&resolve, fullpath, PATH_NOFLAGS, &vmp, &vp);
resolve.l_vmnt_lock = VMNT_READ;
resolve.l_vnode_lock = VNODE_READ;
if (fetch_name(vname1, vname1_length, fullpath) != OK) return(err_code);
if ((vp = eat_path(&resolve, fp)) == NULL) return(err_code);
r = fill_statvfs(vp->v_vmnt, who_e, statbuf, flags);
unlock_vnode(vp);
unlock_vmnt(vmp);
put_vnode(vp);
return r;
}
/*===========================================================================*
* do_fstatvfs *
*===========================================================================*/
int do_fstatvfs(void)
{
/* Perform the fstatvfs1(fd, buf, flags) system call. */
register struct filp *rfilp;
int r, rfd, flags;
vir_bytes statbuf;
rfd = job_m_in.VFS_STATVFS1_FD;
statbuf = (vir_bytes) job_m_in.VFS_STATVFS1_BUF;
flags = job_m_in.VFS_STATVFS1_FLAGS;
/* Is the file descriptor valid? */
if ((rfilp = get_filp(rfd, VNODE_READ)) == NULL) return(err_code);
r = fill_statvfs(rfilp->filp_vno->v_vmnt, who_e, statbuf, flags);
unlock_filp(rfilp);
return(r);
}
/*===========================================================================*
* do_getvfsstat *
*===========================================================================*/
int do_getvfsstat(void)
{
/* Perform the getvfsstat(buf, bufsize, flags) system call. */
struct vmnt *vmp;
vir_bytes buf;
size_t bufsize;
int r, flags, count, do_lock;
buf = (vir_bytes) job_m_in.VFS_GETVFSSTAT_BUF;
bufsize = job_m_in.VFS_GETVFSSTAT_LEN;
flags = job_m_in.VFS_GETVFSSTAT_FLAGS;
count = 0;
if (buf != 0) {
/* We only need to lock target file systems if we are going to query
* them. This will only happen if ST_NOWAIT is not given. If we do
* not lock, we rely on the VMNT_CANSTAT flag to protect us from
* concurrent (un)mount operations. Note that procfs relies on
* ST_NOWAIT calls being lock free, as it is a file system itself.
*/
do_lock = !(flags & ST_NOWAIT);
for (vmp = &vmnt[0]; vmp < &vmnt[NR_MNTS]; vmp++) {
/* If there is no more space, return the count so far. */
if (bufsize < sizeof(struct statvfs))
break;
/* Lock the file system before checking any fields. */
if (do_lock && (r = lock_vmnt(vmp, VMNT_READ)) != OK)
return r;
/* Obtain information for this file system, if it is in use and
* can be reported. File systems that are being (un)mounted
* are skipped, as is PFS. The fill call will block only if
* ST_NOWAIT was not given.
*/
if (vmp->m_dev != NO_DEV && (vmp->m_flags & VMNT_CANSTAT)) {
if ((r = fill_statvfs(vmp, who_e, buf, flags)) != OK) {
if (do_lock)
unlock_vmnt(vmp);
return r;
}
count++;
buf += sizeof(struct statvfs);
bufsize -= sizeof(struct statvfs);
}
if (do_lock)
unlock_vmnt(vmp);
}
} else {
/* Just report a file system count. No need to lock, as above. */
for (vmp = &vmnt[0]; vmp < &vmnt[NR_MNTS]; vmp++) {
if (vmp->m_dev != NO_DEV && (vmp->m_flags & VMNT_CANSTAT))
count++;
}
}
return count;
}
/*===========================================================================*
* do_lstat *
*===========================================================================*/
int do_lstat(void)
{
/* Perform the lstat(name, buf) system call. */
struct vnode *vp;
struct vmnt *vmp;
int r;
char fullpath[PATH_MAX];
struct lookup resolve;
vir_bytes vname1, statbuf;
size_t vname1_length;
vname1 = (vir_bytes) job_m_in.VFS_STAT_NAME;
vname1_length = (size_t) job_m_in.VFS_STAT_LEN;
statbuf = (vir_bytes) job_m_in.VFS_STAT_BUF;
lookup_init(&resolve, fullpath, PATH_RET_SYMLINK, &vmp, &vp);
resolve.l_vmnt_lock = VMNT_READ;
resolve.l_vnode_lock = VNODE_READ;
if (fetch_name(vname1, vname1_length, fullpath) != OK) return(err_code);
if ((vp = eat_path(&resolve, fp)) == NULL) return(err_code);
r = req_stat(vp->v_fs_e, vp->v_inode_nr, who_e, statbuf);
unlock_vnode(vp);
unlock_vmnt(vmp);
put_vnode(vp);
return(r);
}
Reference in a new issue View git blame Copy permalink