/*
* Copyright (c) 2008 Jakub Jermar
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* - The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/** @addtogroup fs
* @{
*/
/**
* @file vfs_ops.c
* @brief Operations that VFS offers to its clients.
*/
#include <ipc/ipc.h>
#include <async.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <bool.h>
#include <futex.h>
#include <rwlock.h>
#include <libadt/list.h>
#include <unistd.h>
#include <ctype.h>
#include <assert.h>
#include <atomic.h>
#include "vfs.h"
/**
* This rwlock prevents the race between a triplet-to-VFS-node resolution and a
* concurrent VFS operation which modifies the file system namespace.
*/
RWLOCK_INITIALIZE(namespace_rwlock);
atomic_t rootfs_futex = FUTEX_INITIALIZER;
vfs_triplet_t rootfs = {
.fs_handle = 0,
.dev_handle = 0,
.index = 0,
};
static int lookup_root(int fs_handle, int dev_handle, vfs_lookup_res_t *result)
{
vfs_pair_t altroot = {
.fs_handle = fs_handle,
.dev_handle = dev_handle,
};
return vfs_lookup_internal
("/", strlen("/"), L_DIRECTORY
, result
, &altroot);
}
void vfs_mount(ipc_callid_t rid, ipc_call_t *request)
{
int dev_handle;
vfs_node_t *mp_node = NULL;
/*
* We expect the library to do the device-name to device-handle
* translation for us, thus the device handle will arrive as ARG1
* in the request.
*/
dev_handle = IPC_GET_ARG1(*request);
/*
* For now, don't make use of ARG2 and ARG3, but they can be used to
* carry mount options in the future.
*/
ipc_callid_t callid;
size_t size;
/*
* Now, we expect the client to send us data with the name of the file
* system.
*/
if (!ipc_data_write_receive(&callid, &size)) {
ipc_answer_0(callid, EINVAL);
ipc_answer_0(rid, EINVAL);
return;
}
/*
* Don't receive more than is necessary for storing a full file system
* name.
*/
if (size < 1 || size > FS_NAME_MAXLEN) {
ipc_answer_0(callid, EINVAL);
ipc_answer_0(rid, EINVAL);
return;
}
/*
* Deliver the file system name.
*/
char fs_name[FS_NAME_MAXLEN + 1];
(void) ipc_data_write_finalize(callid, fs_name, size);
fs_name[size] = '\0';
/*
* Check if we know a file system with the same name as is in fs_name.
* This will also give us its file system handle.
*/
int fs_handle = fs_name_to_handle(fs_name, true);
if (!fs_handle) {
ipc_answer_0(rid, ENOENT);
return;
}
/*
* Now, we want the client to send us the mount point.
*/
if (!ipc_data_write_receive(&callid, &size)) {
ipc_answer_0(callid, EINVAL);
ipc_answer_0(rid, EINVAL);
return;
}
/*
* Check whether size is reasonable wrt. the mount point.
*/
if (size < 1 || size > MAX_PATH_LEN) {
ipc_answer_0(callid, EINVAL);
ipc_answer_0(rid, EINVAL);
return;
}
/*
* Allocate buffer for the mount point data being received.
*/
uint8_t *buf;
if (!buf) {
ipc_answer_0(callid, ENOMEM);
ipc_answer_0(rid, ENOMEM);
return;
}
/*
* Deliver the mount point.
*/
(void) ipc_data_write_finalize(callid, buf, size);
/*
* Lookup the root node of the filesystem being mounted.
* In this case, we don't need to take the namespace_futex as the root
* node cannot be removed. However, we do take a reference to it so
* that we can track how many times it has been mounted.
*/
int rc;
vfs_lookup_res_t mr_res;
rc = lookup_root(fs_handle, dev_handle, &mr_res);
if (rc != EOK) {
ipc_answer_0(rid, rc);
return;
}
vfs_node_t *mr_node = vfs_node_get(&mr_res);
if (!mr_node) {
ipc_answer_0(rid, ENOMEM);
return;
}
/*
* Finally, we need to resolve the path to the mountpoint.
*/
vfs_lookup_res_t mp_res;
futex_down(&rootfs_futex);
if (rootfs.fs_handle) {
/*
* We already have the root FS.
*/
rwlock_write_lock(&namespace_rwlock);
rc = vfs_lookup_internal(buf, size, L_DIRECTORY, &mp_res,
NULL);
if (rc != EOK) {
/*
* The lookup failed for some reason.
*/
rwlock_write_unlock(&namespace_rwlock);
futex_up(&rootfs_futex);
vfs_node_put(mr_node); /* failed -> drop reference */
ipc_answer_0(rid, rc);
return;
}
mp_node = vfs_node_get(&mp_res);
if (!mp_node) {
rwlock_write_unlock(&namespace_rwlock);
futex_up(&rootfs_futex);
vfs_node_put(mr_node); /* failed -> drop reference */
ipc_answer_0(rid, ENOMEM);
return;
}
/*
* Now we hold a reference to mp_node.
* It will be dropped upon the corresponding VFS_UNMOUNT.
* This prevents the mount point from being deleted.
*/
rwlock_write_unlock(&namespace_rwlock);
} else {
/*
* We still don't have the root file system mounted.
*/
if ((size == 1) && (buf[0] == '/')) {
/*
* For this simple, but important case, we are done.
*/
rootfs = mr_res.triplet;
futex_up(&rootfs_futex);
ipc_answer_0(rid, EOK);
return;
} else {
/*
* We can't resolve this without the root filesystem
* being mounted first.
*/
futex_up(&rootfs_futex);
vfs_node_put(mr_node); /* failed -> drop reference */
ipc_answer_0(rid, ENOENT);
return;
}
}
futex_up(&rootfs_futex);
free(buf
); /* The buffer is not needed anymore. */
/*
* At this point, we have all necessary pieces: file system and device
* handles, and we know the mount point VFS node and also the root node
* of the file system being mounted.
*/
int phone = vfs_grab_phone(mp_res.triplet.fs_handle);
/* Later we can use ARG3 to pass mode/flags. */
aid_t req1 = async_send_3(phone, VFS_MOUNT,
(ipcarg_t) mp_res.triplet.dev_handle,
(ipcarg_t) mp_res.triplet.index, 0, NULL);
/* The second call uses the same method. */
aid_t req2 = async_send_3(phone, VFS_MOUNT,
(ipcarg_t) mr_res.triplet.fs_handle,
(ipcarg_t) mr_res.triplet.dev_handle,
(ipcarg_t) mr_res.triplet.index, NULL);
vfs_release_phone(phone);
ipcarg_t rc1;
ipcarg_t rc2;
async_wait_for(req1, &rc1);
async_wait_for(req2, &rc2);
if ((rc1 != EOK) || (rc2 != EOK)) {
/* Mount failed, drop references to mr_node and mp_node. */
vfs_node_put(mr_node);
if (mp_node)
vfs_node_put(mp_node);
}
if (rc2 == EOK)
ipc_answer_0(rid, rc1);
else if (rc1 == EOK)
ipc_answer_0(rid, rc2);
else
ipc_answer_0(rid, rc1);
}
void vfs_open(ipc_callid_t rid, ipc_call_t *request)
{
if (!vfs_files_init()) {
ipc_answer_0(rid, ENOMEM);
return;
}
/*
* The POSIX interface is open(path, oflag, mode).
* We can receive oflags and mode along with the VFS_OPEN call; the path
* will need to arrive in another call.
*
* We also receive one private, non-POSIX set of flags called lflag
* used to pass information to vfs_lookup_internal().
*/
int lflag = IPC_GET_ARG1(*request);
int oflag = IPC_GET_ARG2(*request);
int mode = IPC_GET_ARG3(*request);
size_t len;
ipc_callid_t callid;
if (!ipc_data_write_receive(&callid, &len)) {
ipc_answer_0(callid, EINVAL);
ipc_answer_0(rid, EINVAL);
return;
}
/*
* Now we are on the verge of accepting the path.
*
* There is one optimization we could do in the future: copy the path
* directly into the PLB using some kind of a callback.
*/
if (!path) {
ipc_answer_0(callid, ENOMEM);
ipc_answer_0(rid, ENOMEM);
return;
}
int rc;
if ((rc = ipc_data_write_finalize(callid, path, len))) {
ipc_answer_0(rid, rc);
return;
}
/*
* Avoid the race condition in which the file can be deleted before we
* find/create-and-lock the VFS node corresponding to the looked-up
* triplet.
*/
rwlock_read_lock(&namespace_rwlock);
/*
* The path is now populated and we can call vfs_lookup_internal().
*/
vfs_lookup_res_t lr;
rc = vfs_lookup_internal(path, len, lflag, &lr, NULL);
if (rc) {
rwlock_read_unlock(&namespace_rwlock);
ipc_answer_0(rid, rc);
return;
}
/*
* Path is no longer needed.
*/
vfs_node_t *node = vfs_node_get(&lr);
rwlock_read_unlock(&namespace_rwlock);
/*
* Get ourselves a file descriptor and the corresponding vfs_file_t
* structure.
*/
int fd = vfs_fd_alloc();
if (fd < 0) {
vfs_node_put(node);
ipc_answer_0(rid, fd);
return;
}
vfs_file_t *file = vfs_file_get(fd);
file->node = node;
/*
* The following increase in reference count is for the fact that the
* file is being opened and that a file structure is pointing to it.
* It is necessary so that the file will not disappear when
* vfs_node_put() is called. The reference will be dropped by the
* respective VFS_CLOSE.
*/
vfs_node_addref(node);
vfs_node_put(node);
/*
* Success! Return the new file descriptor to the client.
*/
ipc_answer_1(rid, EOK, fd);
}
static void vfs_rdwr(ipc_callid_t rid, ipc_call_t *request, bool read)
{
/*
* The following code strongly depends on the fact that the files data
* structure can be only accessed by a single fibril and all file
* operations are serialized (i.e. the reads and writes cannot
* interleave and a file cannot be closed while it is being read).
*
* Additional synchronization needs to be added once the table of
* open files supports parallel access!
*/
int fd = IPC_GET_ARG1(*request);
/*
* Lookup the file structure corresponding to the file descriptor.
*/
vfs_file_t *file = vfs_file_get(fd);
if (!file) {
ipc_answer_0(rid, ENOENT);
return;
}
/*
* Now we need to receive a call with client's
* IPC_M_DATA_READ/IPC_M_DATA_WRITE request.
*/
ipc_callid_t callid;
int res;
if (read)
res = ipc_data_read_receive(&callid, NULL);
else
res = ipc_data_write_receive(&callid, NULL);
if (!res) {
ipc_answer_0(callid, EINVAL);
ipc_answer_0(rid, EINVAL);
return;
}
/*
* Lock the open file structure so that no other thread can manipulate
* the same open file at a time.
*/
futex_down(&file->lock);
/*
* Lock the file's node so that no other client can read/write to it at
* the same time.
*/
if (read)
rwlock_read_lock(&file->node->contents_rwlock);
else
rwlock_write_lock(&file->node->contents_rwlock);
int fs_phone = vfs_grab_phone(file->node->fs_handle);
/*
* Make a VFS_READ/VFS_WRITE request at the destination FS server.
*/
aid_t msg;
ipc_call_t answer;
msg = async_send_3(fs_phone, IPC_GET_METHOD(*request),
file->node->dev_handle, file->node->index, file->pos, &answer);
/*
* Forward the IPC_M_DATA_READ/IPC_M_DATA_WRITE request to the
* destination FS server. The call will be routed as if sent by
* ourselves. Note that call arguments are immutable in this case so we
* don't have to bother.
*/
ipc_forward_fast(callid, fs_phone, 0, 0, 0, IPC_FF_ROUTE_FROM_ME);
vfs_release_phone(fs_phone);
/*
* Wait for reply from the FS server.
*/
ipcarg_t rc;
async_wait_for(msg, &rc);
size_t bytes = IPC_GET_ARG1(answer);
/*
* Unlock the VFS node.
*/
if (read)
rwlock_read_unlock(&file->node->contents_rwlock);
else {
/* Update the cached version of node's size. */
file->node->size = IPC_GET_ARG2(answer);
rwlock_write_unlock(&file->node->contents_rwlock);
}
/*
* Update the position pointer and unlock the open file.
*/
file->pos += bytes;
futex_up(&file->lock);
/*
* FS server's reply is the final result of the whole operation we
* return to the client.
*/
ipc_answer_1(rid, rc, bytes);
}
void vfs_read(ipc_callid_t rid, ipc_call_t *request)
{
vfs_rdwr(rid, request, true);
}
void vfs_write(ipc_callid_t rid, ipc_call_t *request)
{
vfs_rdwr(rid, request, false);
}
void vfs_seek(ipc_callid_t rid, ipc_call_t *request)
{
int fd = (int) IPC_GET_ARG1(*request);
off_t off = (off_t) IPC_GET_ARG2(*request);
int whence = (int) IPC_GET_ARG3(*request);
/*
* Lookup the file structure corresponding to the file descriptor.
*/
vfs_file_t *file = vfs_file_get(fd);
if (!file) {
ipc_answer_0(rid, ENOENT);
return;
}
off_t newpos;
futex_down(&file->lock);
if (whence == SEEK_SET) {
file->pos = off;
futex_up(&file->lock);
ipc_answer_1(rid, EOK, off);
return;
}
if (whence == SEEK_CUR) {
if (file->pos + off < file->pos) {
futex_up(&file->lock);
ipc_answer_0(rid, EOVERFLOW);
return;
}
file->pos += off;
newpos = file->pos;
futex_up(&file->lock);
ipc_answer_1(rid, EOK, newpos);
return;
}
if (whence == SEEK_END) {
rwlock_read_lock(&file->node->contents_rwlock);
size_t size = file->node->size;
rwlock_read_unlock(&file->node->contents_rwlock);
if (size + off < size) {
futex_up(&file->lock);
ipc_answer_0(rid, EOVERFLOW);
return;
}
newpos = size + off;
futex_up(&file->lock);
ipc_answer_1(rid, EOK, newpos);
return;
}
futex_up(&file->lock);
ipc_answer_0(rid, EINVAL);
}
void vfs_truncate(ipc_callid_t rid, ipc_call_t *request)
{
int fd = IPC_GET_ARG1(*request);
size_t size = IPC_GET_ARG2(*request);
ipcarg_t rc;
vfs_file_t *file = vfs_file_get(fd);
if (!file) {
ipc_answer_0(rid, ENOENT);
return;
}
futex_down(&file->lock);
rwlock_write_lock(&file->node->contents_rwlock);
int fs_phone = vfs_grab_phone(file->node->fs_handle);
rc = async_req_3_0(fs_phone, VFS_TRUNCATE, (ipcarg_t)file->node->dev_handle,
(ipcarg_t)file->node->index, (ipcarg_t)size);
vfs_release_phone(fs_phone);
if (rc == EOK)
file->node->size = size;
rwlock_write_unlock(&file->node->contents_rwlock);
futex_up(&file->lock);
ipc_answer_0(rid, rc);
}
/**
* @}
*/