/*
* 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 <ipc/services.h>
#include <async.h>
#include <fibril.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 <as.h>
#include <assert.h>
#include <atomic.h>
#include "vfs.h"
#define min(a, b) ((a) < (b) ? (a) : (b))
/**
* 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 plb_futex = FUTEX_INITIALIZER;
link_t plb_head; /**< PLB entry ring buffer. */
uint8_t *plb = NULL;
/** Perform a path lookup.
*
* @param path Path to be resolved; it needn't be an ASCIIZ string.
* @param len Number of path characters pointed by path.
* @param result Empty node structure where the result will be stored.
* @param size Storage where the size of the node will be stored. Can
* be NULL.
* @param altroot If non-empty, will be used instead of rootfs as the root
* of the whole VFS tree.
*
* @return EOK on success or an error code from errno.h.
*/
int vfs_lookup_internal(char *path, size_t len, vfs_triplet_t *result,
size_t *size, vfs_pair_t *altroot)
{
vfs_pair_t *root;
if (!len)
return EINVAL;
if (altroot)
root = altroot;
else
root = (vfs_pair_t *) &rootfs;
if (!root->fs_handle)
return ENOENT;
futex_down(&plb_futex);
plb_entry_t entry;
link_initialize(&entry.plb_link);
entry.len = len;
off_t first; /* the first free index */
off_t last; /* the last free index */
if (list_empty(&plb_head)) {
first = 0;
last = PLB_SIZE - 1;
} else {
plb_entry_t *oldest = list_get_instance(plb_head.next,
plb_entry_t, plb_link);
plb_entry_t *newest = list_get_instance(plb_head.prev,
plb_entry_t, plb_link);
first = (newest->index + newest->len) % PLB_SIZE;
last = (oldest->index - 1) % PLB_SIZE;
}
if (first <= last) {
if ((last - first) + 1 < len) {
/*
* The buffer cannot absorb the path.
*/
futex_up(&plb_futex);
return ELIMIT;
}
} else {
if (PLB_SIZE - ((first - last) + 1) < len) {
/*
* The buffer cannot absorb the path.
*/
futex_up(&plb_futex);
return ELIMIT;
}
}
/*
* We know the first free index in PLB and we also know that there is
* enough space in the buffer to hold our path.
*/
entry.index = first;
entry.len = len;
/*
* Claim PLB space by inserting the entry into the PLB entry ring
* buffer.
*/
list_append(&entry.plb_link, &plb_head);
futex_up(&plb_futex);
/*
* Copy the path into PLB.
*/
size_t cnt1 = min(len, (PLB_SIZE - first) + 1);
size_t cnt2 = len - cnt1;
memcpy(&plb
[first
], path
, cnt1
); memcpy(plb
, &path
[cnt1
], cnt2
);
ipc_call_t answer;
int phone = vfs_grab_phone(root->fs_handle);
aid_t req = async_send_3(phone, VFS_LOOKUP, (ipcarg_t) first,
(ipcarg_t) (first + len - 1) % PLB_SIZE,
(ipcarg_t) root->dev_handle, &answer);
vfs_release_phone(phone);
ipcarg_t rc;
async_wait_for(req, &rc);
futex_down(&plb_futex);
list_remove(&entry.plb_link);
/*
* Erasing the path from PLB will come handy for debugging purposes.
*/
futex_up(&plb_futex);
if (rc == EOK) {
result->fs_handle = (int) IPC_GET_ARG1(answer);
result->dev_handle = (int) IPC_GET_ARG2(answer);
result->index = (int) IPC_GET_ARG3(answer);
if (size)
*size = (size_t) IPC_GET_ARG4(answer);
}
return rc;
}
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_triplet_t *root,
size_t *size)
{
vfs_pair_t altroot = {
.fs_handle = fs_handle,
.dev_handle = dev_handle,
};
return vfs_lookup_internal
("/", strlen("/"), root
, size
, &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_triplet_t mounted_root;
size_t mrsz;
rc = lookup_root(fs_handle, dev_handle, &mounted_root, &mrsz);
if (rc != EOK) {
ipc_answer_0(rid, rc);
return;
}
vfs_node_t *mr_node = vfs_node_get(&mounted_root, mrsz);
if (!mr_node) {
ipc_answer_0(rid, ENOMEM);
return;
}
/*
* Finally, we need to resolve the path to the mountpoint.
*/
vfs_triplet_t mp;
size_t mpsz;
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, &mp, &mpsz, 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, mpsz);
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 = mounted_root;
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.fs_handle);
/* Later we can use ARG3 to pass mode/flags. */
aid_t req1 = async_send_3(phone, VFS_MOUNT, (ipcarg_t) mp.dev_handle,
(ipcarg_t) mp.index, 0, NULL);
/* The second call uses the same method. */
aid_t req2 = async_send_3(phone, VFS_MOUNT,
(ipcarg_t) mounted_root.fs_handle,
(ipcarg_t) mounted_root.dev_handle, (ipcarg_t) mounted_root.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, flags, mode).
* We can receive flags and mode along with the VFS_OPEN call; the path
* will need to arrive in another call.
*/
int flags = IPC_GET_ARG1(*request);
int mode = IPC_GET_ARG2(*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_triplet_t triplet;
size_t size;
rc = vfs_lookup_internal(path, len, &triplet, &size, 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(&triplet, size);
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);
}
atomic_t fs_head_futex = FUTEX_INITIALIZER;
link_t fs_head;
atomic_t fs_handle_next = {
.count = 1
};
/** Verify the VFS info structure.
*
* @param info Info structure to be verified.
*
* @return Non-zero if the info structure is sane, zero otherwise.
*/
static bool vfs_info_sane(vfs_info_t *info)
{
int i;
/*
* Check if the name is non-empty and is composed solely of ASCII
* characters [a-z]+[a-z0-9_-]*.
*/
dprintf("The name doesn't start with a lowercase character.\n");
return false;
}
for (i = 1; i < FS_NAME_MAXLEN; i++) {
(info->name[i] != '-') && (info->name[i] != '_')) {
if (info->name[i] == '\0') {
break;
} else {
dprintf("The name contains illegal "
"characters.\n");
return false;
}
}
}
/*
* This check is not redundant. It ensures that the name is
* NULL-terminated, even if FS_NAME_MAXLEN characters are used.
*/
if (info->name[i] != '\0') {
dprintf("The name is not properly NULL-terminated.\n");
return false;
}
/*
* Check if the FS implements mandatory VFS operations.
*/
if (info->ops[IPC_METHOD_TO_VFS_OP(VFS_REGISTER)] != VFS_OP_DEFINED) {
dprintf("Operation VFS_REGISTER not defined by the client.\n");
return false;
}
if (info->ops[IPC_METHOD_TO_VFS_OP(VFS_MOUNT)] != VFS_OP_DEFINED) {
dprintf("Operation VFS_MOUNT not defined by the client.\n");
return false;
}
if (info->ops[IPC_METHOD_TO_VFS_OP(VFS_UNMOUNT)] != VFS_OP_DEFINED) {
dprintf("Operation VFS_UNMOUNT not defined by the client.\n");
return false;
}
if (info->ops[IPC_METHOD_TO_VFS_OP(VFS_LOOKUP)] != VFS_OP_DEFINED) {
dprintf("Operation VFS_LOOKUP not defined by the client.\n");
return false;
}
if (info->ops[IPC_METHOD_TO_VFS_OP(VFS_OPEN)] != VFS_OP_DEFINED) {
dprintf("Operation VFS_OPEN not defined by the client.\n");
return false;
}
if (info->ops[IPC_METHOD_TO_VFS_OP(VFS_CLOSE)] != VFS_OP_DEFINED) {
dprintf("Operation VFS_CLOSE not defined by the client.\n");
return false;
}
if (info->ops[IPC_METHOD_TO_VFS_OP(VFS_READ)] != VFS_OP_DEFINED) {
dprintf("Operation VFS_READ not defined by the client.\n");
return false;
}
/*
* Check if each operation is either not defined, defined or default.
*/
for (i = VFS_FIRST; i < VFS_LAST; i++) {
if ((info->ops[IPC_METHOD_TO_VFS_OP(i)] != VFS_OP_NULL) &&
(info->ops[IPC_METHOD_TO_VFS_OP(i)] != VFS_OP_DEFAULT) &&
(info->ops[IPC_METHOD_TO_VFS_OP(i)] != VFS_OP_DEFINED)) {
dprintf("Operation info not understood.\n");
return false;
}
}
return true;
}
/** VFS_REGISTER protocol function.
*
* @param rid Hash of the call with the request.
* @param request Call structure with the request.
*/
void vfs_register(ipc_callid_t rid, ipc_call_t *request)
{
ipc_callid_t callid;
ipc_call_t call;
int rc;
size_t size;
dprintf("Processing VFS_REGISTER request received from %p.\n",
request->in_phone_hash);
/*
* The first call has to be IPC_M_DATA_SEND in which we receive the
* VFS info structure from the client FS.
*/
if (!ipc_data_write_receive(&callid, &size)) {
/*
* The client doesn't obey the same protocol as we do.
*/
dprintf("Receiving of VFS info failed.\n");
ipc_answer_0(callid, EINVAL);
ipc_answer_0(rid, EINVAL);
return;
}
dprintf("VFS info received, size = %d\n", size);
/*
* We know the size of the VFS info structure. See if the client
* understands this easy concept too.
*/
if (size != sizeof(vfs_info_t)) {
/*
* The client is sending us something, which cannot be
* the info structure.
*/
dprintf("Received VFS info has bad size.\n");
ipc_answer_0(callid, EINVAL);
ipc_answer_0(rid, EINVAL);
return;
}
/*
* Allocate and initialize a buffer for the fs_info structure.
*/
fs_info_t *fs_info;
fs_info
= (fs_info_t
*) malloc(sizeof(fs_info_t
)); if (!fs_info) {
dprintf("Could not allocate memory for FS info.\n");
ipc_answer_0(callid, ENOMEM);
ipc_answer_0(rid, ENOMEM);
return;
}
link_initialize(&fs_info->fs_link);
futex_initialize(&fs_info->phone_futex, 1);
rc = ipc_data_write_finalize(callid, &fs_info->vfs_info, size);
if (rc != EOK) {
dprintf("Failed to deliver the VFS info into our AS, rc=%d.\n",
rc);
ipc_answer_0(callid, rc);
ipc_answer_0(rid, rc);
return;
}
dprintf("VFS info delivered.\n");
if (!vfs_info_sane(&fs_info->vfs_info)) {
ipc_answer_0(callid, EINVAL);
ipc_answer_0(rid, EINVAL);
return;
}
futex_down(&fs_head_futex);
/*
* Check for duplicit registrations.
*/
if (fs_name_to_handle(fs_info->vfs_info.name, false)) {
/*
* We already register a fs like this.
*/
dprintf("FS is already registered.\n");
futex_up(&fs_head_futex);
ipc_answer_0(callid, EEXISTS);
ipc_answer_0(rid, EEXISTS);
return;
}
/*
* Add fs_info to the list of registered FS's.
*/
dprintf("Inserting FS into the list of registered file systems.\n");
list_append(&fs_info->fs_link, &fs_head);
/*
* Now we want the client to send us the IPC_M_CONNECT_TO_ME call so
* that a callback connection is created and we have a phone through
* which to forward VFS requests to it.
*/
callid = async_get_call(&call);
if (IPC_GET_METHOD(call) != IPC_M_CONNECT_TO_ME) {
dprintf("Unexpected call, method = %d\n", IPC_GET_METHOD(call));
list_remove(&fs_info->fs_link);
futex_up(&fs_head_futex);
ipc_answer_0(callid, EINVAL);
ipc_answer_0(rid, EINVAL);
return;
}
fs_info->phone = IPC_GET_ARG5(call);
ipc_answer_0(callid, EOK);
dprintf("Callback connection to FS created.\n");
/*
* The client will want us to send him the address space area with PLB.
*/
if (!ipc_share_in_receive(&callid, &size)) {
dprintf("Unexpected call, method = %d\n", IPC_GET_METHOD(call));
list_remove(&fs_info->fs_link);
futex_up(&fs_head_futex);
ipc_hangup(fs_info->phone);
ipc_answer_0(callid, EINVAL);
ipc_answer_0(rid, EINVAL);
return;
}
/*
* We can only send the client address space area PLB_SIZE bytes long.
*/
if (size != PLB_SIZE) {
dprintf("Client suggests wrong size of PFB, size = %d\n", size);
list_remove(&fs_info->fs_link);
futex_up(&fs_head_futex);
ipc_hangup(fs_info->phone);
ipc_answer_0(callid, EINVAL);
ipc_answer_0(rid, EINVAL);
return;
}
/*
* Commit to read-only sharing the PLB with the client.
*/
(void) ipc_share_in_finalize(callid, plb,
AS_AREA_READ | AS_AREA_CACHEABLE);
dprintf("Sharing PLB.\n");
/*
* That was it. The FS has been registered.
* In reply to the VFS_REGISTER request, we assign the client file
* system a global file system handle.
*/
fs_info->fs_handle = (int) atomic_postinc(&fs_handle_next);
ipc_answer_1(rid, EOK, (ipcarg_t) fs_info->fs_handle);
futex_up(&fs_head_futex);
dprintf("\"%.*s\" filesystem successfully registered, handle=%d.\n",
FS_NAME_MAXLEN, fs_info->vfs_info.name, fs_info->fs_handle);
}
/** For a given file system handle, implement policy for allocating a phone.
*
* @param handle File system handle.
*
* @return Phone over which a multi-call request can be safely
* sent. Return 0 if no phone was found.
*/
int vfs_grab_phone(int handle)
{
/*
* For now, we don't try to be very clever and very fast.
* We simply lookup the phone in the fs_head list. We currently don't
* open any additional phones (even though that itself would be pretty
* straightforward; housekeeping multiple open phones to a FS task would
* be more demanding). Instead, we simply take the respective
* phone_futex and keep it until vfs_release_phone().
*/
futex_down(&fs_head_futex);
link_t *cur;
fs_info_t *fs;
for (cur = fs_head.next; cur != &fs_head; cur = cur->next) {
fs = list_get_instance(cur, fs_info_t, fs_link);
if (fs->fs_handle == handle) {
futex_up(&fs_head_futex);
/*
* For now, take the futex unconditionally.
* Oh yeah, serialization rocks.
* It will be up'ed in vfs_release_phone().
*/
futex_down(&fs->phone_futex);
/*
* Avoid deadlock with other fibrils in the same thread
* by disabling fibril preemption.
*/
fibril_inc_sercount();
return fs->phone;
}
}
futex_up(&fs_head_futex);
return 0;
}
/** Tell VFS that the phone is in use for any request.
*
* @param phone Phone to FS task.
*/
void vfs_release_phone(int phone)
{
bool found = false;
/*
* Undo the fibril_inc_sercount() done in vfs_grab_phone().
*/
fibril_dec_sercount();
futex_down(&fs_head_futex);
link_t *cur;
for (cur = fs_head.next; cur != &fs_head; cur = cur->next) {
fs_info_t *fs = list_get_instance(cur, fs_info_t, fs_link);
if (fs->phone == phone) {
found = true;
futex_up(&fs_head_futex);
futex_up(&fs->phone_futex);
return;
}
}
futex_up(&fs_head_futex);
/*
* Not good to get here.
*/
}
/** Convert file system name to its handle.
*
* @param name File system name.
* @param lock If true, the function will down and up the
* fs_head_futex.
*
* @return File system handle or zero if file system not found.
*/
int fs_name_to_handle(char *name, bool lock)
{
int handle = 0;
if (lock)
futex_down(&fs_head_futex);
link_t *cur;
for (cur = fs_head.next; cur != &fs_head; cur = cur->next) {
fs_info_t *fs = list_get_instance(cur, fs_info_t, fs_link);
if (strncmp(fs
->vfs_info.
name, name
, sizeof(fs->vfs_info.name)) == 0) {
handle = fs->fs_handle;
break;
}
}
if (lock)
futex_up(&fs_head_futex);
return handle;
}
/**
* @}
*/