Merge commit '2cedd8f0ecbd2b29bf0aac72bb8b7413b0326938' into merges

[unleashed.git] / kernel / fs / portfs / port_fd.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */


#include <sys/types.h>
#include <sys/systm.h>
#include <sys/stat.h>
#include <sys/errno.h>
#include <sys/kmem.h>
#include <sys/sysmacros.h>
#include <sys/debug.h>
#include <sys/poll_impl.h>
#include <sys/port_impl.h>

#define PORTHASH_START  256     /* start cache space for events */
#define PORTHASH_MULT   2       /* growth threshold and factor */

/* local functions */
static int      port_fd_callback(void *, int *, pid_t, int, void *);
static int      port_bind_pollhead(pollhead_t **, polldat_t *, short *);
static void     port_close_sourcefd(void *, int, pid_t, int);
static void     port_cache_insert_fd(port_fdcache_t *, polldat_t *);

/*
 * port_fd_callback()
 * The event port framework uses callback functions to notify associated
 * event sources about actions on source specific objects.
 * The source itself defines the "arg" required to identify the object with
 * events. In the port_fd_callback() case the "arg" is a pointer to portfd_t
 * structure. The portfd_t structure is specific for PORT_SOURCE_FD source.
 * The port_fd_callback() function is notified in three cases:
 * - PORT_CALLBACK_DEFAULT
 *      The object (fd) will be delivered to the application.
 * - PORT_CALLBACK_DISSOCIATE
 *      The object (fd) will be dissociated from  the port.
 * - PORT_CALLBACK_CLOSE
 *      The object (fd) will be dissociated from the port because the port
 *      is being closed.
 * A fd is shareable between processes only when
 * - processes have the same fd id and
 * - processes have the same fp.
 * A fd becomes shareable:
 * - on fork() across parent and child process and
 * - when I_SENDFD is used to pass file descriptors between parent and child
 *   immediately after fork() (the sender and receiver must get the same
 *   file descriptor id).
 * If a fd is shared between processes, all involved processes will get
 * the same rights related to re-association of the fd with the port and
 * retrieve of events from that fd.
 * The process which associated the fd with a port for the first time
 * becomes also the owner of the association. Only the owner of the
 * association is allowed to dissociate the fd from the port.
 */
/* ARGSUSED */
static int
port_fd_callback(void *arg, int *events, pid_t pid, int flag, void *evp)
{
        portfd_t        *pfd = (portfd_t *)arg;
        polldat_t       *pdp = PFTOD(pfd);
        port_fdcache_t  *pcp;
        file_t          *fp;
        int             error;

        ASSERT((pdp != NULL) && (events != NULL));
        switch (flag) {
        case PORT_CALLBACK_DEFAULT:
                if (curproc->p_pid != pid) {
                        /*
                         * Check if current process is allowed to retrieve
                         * events from this fd.
                         */
                        fp = getf(pdp->pd_fd);
                        if (fp == NULL) {
                                error = EACCES; /* deny delivery of events */
                                break;
                        }
                        releasef(pdp->pd_fd);
                        if (fp != pdp->pd_fp) {
                                error = EACCES; /* deny delivery of events */
                                break;
                        }
                }
                *events = pdp->pd_portev->portkev_events; /* update events */
                error = 0;
                break;
        case PORT_CALLBACK_DISSOCIATE:
                error = 0;
                break;
        case PORT_CALLBACK_CLOSE:
                /* remove polldat/portfd struct */
                pdp->pd_portev = NULL;
                pcp = (port_fdcache_t *)pdp->pd_pcache;
                mutex_enter(&pcp->pc_lock);
                pdp->pd_fp = NULL;
                pdp->pd_events = 0;
                if (pdp->pd_php != NULL) {
                        pollhead_delete(pdp->pd_php, pdp);
                        pdp->pd_php = NULL;
                }
                port_pcache_remove_fd(pcp, pfd);
                mutex_exit(&pcp->pc_lock);
                error = 0;
                break;
        default:
                error = EINVAL;
                break;
        }
        return (error);
}

/*
 * This routine returns a pointer to a cached poll fd entry, or NULL if it
 * does not find it in the hash table.
 * The fd is used as index.
 * The fd and the fp are used to detect a valid entry.
 * This function returns a pointer to a valid portfd_t structure only when
 * the fd and the fp in the args match the entries in polldat_t.
 */
portfd_t *
port_cache_lookup_fp(port_fdcache_t *pcp, int fd, file_t *fp)
{
        polldat_t       *pdp;
        portfd_t        **bucket;

        ASSERT(MUTEX_HELD(&pcp->pc_lock));
        bucket = PORT_FD_BUCKET(pcp, fd);
        pdp = PFTOD(*bucket);
        while (pdp != NULL) {
                if (pdp->pd_fd == fd && pdp->pd_fp == fp)
                        break;
                pdp = pdp->pd_hashnext;
        }
        return (PDTOF(pdp));
}

/*
 * port_associate_fd()
 * This function associates new file descriptors with a port or
 * reactivate already associated file descriptors.
 * The reactivation also updates the events types to be checked and the
 * attached user pointer.
 * Per port a cache is used to store associated file descriptors.
 * Internally the fop_poll interface is used to poll for existing events.
 * The fop_poll interface can also deliver a pointer to a pollhead_t structure
 * which is used to enqueue polldat_t structures with pending events.
 * If fop_poll immediately returns valid events (revents) then those events
 * will be submitted to the event port with port_send_event().
 * Otherwise fop_poll does not return events but it delivers a pointer to a
 * pollhead_t structure. In such a case the corresponding file system behind
 * fop_poll will use the pollwakeup() function to notify about existing
 * events.
 */
int
port_associate_fd(port_t *pp, int source, uintptr_t object, int events,
    void *user)
{
        port_fdcache_t  *pcp;
        int             fd;
        struct pollhead *php = NULL;
        portfd_t        *pfd;
        polldat_t       *pdp;
        file_t          *fp;
        port_kevent_t   *pkevp;
        short           revents;
        int             error = 0;
        int             active;

        pcp = pp->port_queue.portq_pcp;
        if (object > (uintptr_t)INT_MAX)
                return (EBADFD);

        fd = object;

        if ((fp = getf(fd)) == NULL)
                return (EBADFD);

        mutex_enter(&pcp->pc_lock);

        if (pcp->pc_hash == NULL) {
                /*
                 * This is the first time that a fd is being associated with
                 * the current port:
                 * - create PORT_SOURCE_FD cache
                 * - associate PORT_SOURCE_FD source with the port
                 */
                error = port_associate_ksource(pp->port_fd, PORT_SOURCE_FD,
                    NULL, port_close_sourcefd, pp, NULL);
                if (error) {
                        mutex_exit(&pcp->pc_lock);
                        releasef(fd);
                        return (error);
                }

                /* create polldat cache */
                pcp->pc_hashsize = PORTHASH_START;
                pcp->pc_hash = kmem_zalloc(pcp->pc_hashsize *
                    sizeof (portfd_t *), KM_SLEEP);
                pfd = NULL;
        } else {
                /* Check if the fd/fp is already associated with the port */
                pfd = port_cache_lookup_fp(pcp, fd, fp);
        }

        if (pfd == NULL) {
                /*
                 * new entry
                 * Allocate a polldat_t structure per fd
                 * The use of the polldat_t structure to cache file descriptors
                 * is required to be able to share the pollwakeup() function
                 * with poll(2) and devpoll(7d).
                 */
                pfd = kmem_zalloc(sizeof (portfd_t), KM_SLEEP);
                pdp = PFTOD(pfd);
                pdp->pd_fd = fd;
                pdp->pd_fp = fp;
                pdp->pd_pcache = (void *)pcp;

                /* Allocate a port event structure per fd */
                error = port_alloc_event_local(pp, source, PORT_ALLOC_CACHED,
                    &pdp->pd_portev);
                if (error) {
                        kmem_free(pfd, sizeof (portfd_t));
                        releasef(fd);
                        mutex_exit(&pcp->pc_lock);
                        return (error);
                }
                pkevp = pdp->pd_portev;
                pkevp->portkev_callback = port_fd_callback;
                pkevp->portkev_arg = pfd;

                /* add portfd_t entry  to the cache */
                port_cache_insert_fd(pcp, pdp);
                pkevp->portkev_object = fd;
                pkevp->portkev_user = user;

                /*
                 * Add current port to the file descriptor interested list
                 * The members of the list are notified when the file descriptor
                 * is closed.
                 */
                addfd_port(fd, pfd);
        } else {
                /*
                 * The file descriptor is already associated with the port
                 */
                pdp = PFTOD(pfd);
                pkevp = pdp->pd_portev;

                /*
                 * Check if the re-association happens before the last
                 * submitted event of the file descriptor was retrieved.
                 * Clear the PORT_KEV_VALID flag if set. No new events
                 * should get submitted after this flag is cleared.
                 */
                mutex_enter(&pkevp->portkev_lock);
                if (pkevp->portkev_flags & PORT_KEV_VALID) {
                        pkevp->portkev_flags &= ~PORT_KEV_VALID;
                }
                if (pkevp->portkev_flags & PORT_KEV_DONEQ) {
                        mutex_exit(&pkevp->portkev_lock);
                        /*
                         * Remove any events that where already fired
                         * for this fd and are still in the port queue.
                         */
                        (void) port_remove_done_event(pkevp);
                } else {
                        mutex_exit(&pkevp->portkev_lock);
                }
                pkevp->portkev_user = user;
        }

        pfd->pfd_thread = curthread;
        mutex_enter(&pkevp->portkev_lock);
        pkevp->portkev_events = 0;      /* no fired events */
        pdp->pd_events = events;        /* events associated */
        /*
         * allow new events.
         */
        pkevp->portkev_flags |= PORT_KEV_VALID;
        mutex_exit(&pkevp->portkev_lock);

        /*
         * do fop_poll and cache this poll fd.
         *
         * XXX - pollrelock() logic needs to know
         * which pollcache lock to grab. It'd be a
         * cleaner solution if we could pass pcp as
         * an arguement in fop_poll interface instead
         * of implicitly passing it using thread_t
         * struct. On the other hand, changing fop_poll
         * interface will require all driver/file system
         * poll routine to change.
         */
        curthread->t_pollcache = (pollcache_t *)pcp;
        error = fop_poll(fp->f_vnode, events, 0, &revents, &php, NULL);
        curthread->t_pollcache = NULL;

        /*
         * The pc_lock can get dropped and reaquired in fop_poll.
         * In the window pc_lock is dropped another thread in
         * port_dissociate can remove the pfd from the port cache
         * and free the pfd.
         * It is also possible for another thread to sneak in and do a
         * port_associate on the same fd during the same window.
         * For both these cases return the current value of error.
         * The application should take care to ensure that the threads
         * do not race with each other for association and disassociation
         * of the same fd.
         */
        if (((pfd = port_cache_lookup_fp(pcp, fd, fp)) == NULL) ||
            (pfd->pfd_thread != curthread)) {
                releasef(fd);
                mutex_exit(&pcp->pc_lock);
                return (error);
        }

        /*
         * To keep synchronization between fop_poll above and
         * pollhead_insert below, it is necessary to
         * call fop_poll() again (see port_bind_pollhead()).
         */
        if (error) {
                goto errout;
        }

        if (php != NULL && (pdp->pd_php != php)) {
                /*
                 * No events delivered yet.
                 * Bind pollhead pointer with current polldat_t structure.
                 * Sub-system will call pollwakeup() later with php as
                 * argument.
                 */
                error = port_bind_pollhead(&php, pdp, &revents);
                /*
                 * The pc_lock can get dropped and reaquired in fop_poll.
                 * In the window pc_lock is dropped another thread in
                 * port_dissociate can remove the pfd from the port cache
                 * and free the pfd.
                 * It is also possible for another thread to sneak in and do a
                 * port_associate on the same fd during the same window.
                 * For both these cases return the current value of error.
                 * The application should take care to ensure that the threads
                 * do not race with each other for association
                 * and disassociation of the same fd.
                 */
                if (((pfd = port_cache_lookup_fp(pcp, fd, fp)) == NULL) ||
                    (pfd->pfd_thread != curthread)) {
                        releasef(fd);
                        mutex_exit(&pcp->pc_lock);
                        return (error);
                }

                if (error) {
                        goto errout;
                }
        }

        /*
         * Check if new events where detected and no events have been
         * delivered. The revents was already set after the fop_poll
         * above or it was updated in port_bind_pollhead().
         */
        mutex_enter(&pkevp->portkev_lock);
        if (revents && (pkevp->portkev_flags & PORT_KEV_VALID)) {
                ASSERT((pkevp->portkev_flags & PORT_KEV_DONEQ) == 0);
                pkevp->portkev_flags &= ~PORT_KEV_VALID;
                revents = revents & (pdp->pd_events | POLLHUP | POLLERR);
                /* send events to the event port */
                pkevp->portkev_events = revents;
                /*
                 * port_send_event will release the portkev_lock mutex.
                 */
                port_send_event(pkevp);
        } else {
                mutex_exit(&pkevp->portkev_lock);
        }

        releasef(fd);
        mutex_exit(&pcp->pc_lock);
        return (error);

errout:
        delfd_port(fd, pfd);
        /*
         * If the portkev is not valid, then an event was
         * delivered.
         *
         * If an event was delivered and got picked up, then
         * we return error = 0 treating this as a successful
         * port associate call. The thread which received
         * the event gets control of the object.
         */
        active = 0;
        mutex_enter(&pkevp->portkev_lock);
        if (pkevp->portkev_flags & PORT_KEV_VALID) {
                pkevp->portkev_flags &= ~PORT_KEV_VALID;
                active = 1;
        }
        mutex_exit(&pkevp->portkev_lock);

        if (!port_remove_fd_object(pfd, pp, pcp) && !active) {
                error = 0;
        }
        releasef(fd);
        mutex_exit(&pcp->pc_lock);
        return (error);
}

/*
 * The port_dissociate_fd() function dissociates the delivered file
 * descriptor from the event port and removes already fired events.
 * If a fd is shared between processes, all involved processes will get
 * the same rights related to re-association of the fd with the port and
 * retrieve of events from that fd.
 * The process which associated the fd with a port for the first time
 * becomes also the owner of the association. Only the owner of the
 * association is allowed to dissociate the fd from the port.
 */
int
port_dissociate_fd(port_t *pp, uintptr_t object)
{
        int             fd;
        port_fdcache_t  *pcp;
        portfd_t        *pfd;
        file_t          *fp;
        int             active;
        port_kevent_t   *pkevp;

        if (object > (uintptr_t)INT_MAX)
                return (EBADFD);

        fd = object;
        pcp = pp->port_queue.portq_pcp;

        mutex_enter(&pcp->pc_lock);
        if (pcp->pc_hash == NULL) {
                /* no file descriptor cache available */
                mutex_exit(&pcp->pc_lock);
                return (ENOENT);
        }
        if ((fp = getf(fd)) == NULL) {
                mutex_exit(&pcp->pc_lock);
                return (EBADFD);
        }
        pfd = port_cache_lookup_fp(pcp, fd, fp);
        if (pfd == NULL) {
                releasef(fd);
                mutex_exit(&pcp->pc_lock);
                return (ENOENT);
        }
        /* only association owner is allowed to remove the association */
        if (curproc->p_pid != PFTOD(pfd)->pd_portev->portkev_pid) {
                releasef(fd);
                mutex_exit(&pcp->pc_lock);
                return (EACCES);
        }

        /* remove port from the file descriptor interested list */
        delfd_port(fd, pfd);

        /*
         * Deactivate the association. No events get posted after
         * this.
         */
        pkevp = PFTOD(pfd)->pd_portev;
        mutex_enter(&pkevp->portkev_lock);
        if (pkevp->portkev_flags & PORT_KEV_VALID) {
                pkevp->portkev_flags &= ~PORT_KEV_VALID;
                active = 1;
        } else {
                active = 0;
        }
        mutex_exit(&pkevp->portkev_lock);

        /* remove polldat & port event structure */
        if (port_remove_fd_object(pfd, pp, pcp)) {
                /*
                 * An event was found and removed from the
                 * port done queue. This means the event has not yet
                 * been retrived. In this case we treat this as an active
                 * association.
                 */
                ASSERT(active == 0);
                active = 1;
        }
        releasef(fd);
        mutex_exit(&pcp->pc_lock);

        /*
         * Return ENOENT if there was no active association.
         */
        return ((active ? 0 : ENOENT));
}

/*
 * Associate event port polldat_t structure with sub-system pointer to
 * a polhead_t structure.
 */
static int
port_bind_pollhead(pollhead_t **php, polldat_t *pdp, short *revents)
{
        int             error;
        file_t          *fp;

        /* polldat_t associated with another pollhead_t pointer */
        if (pdp->pd_php != NULL)
                pollhead_delete(pdp->pd_php, pdp);

        /*
         * Before pollhead_insert() pollwakeup() will not detect a polldat
         * entry in the ph_list and the event notification will disappear.
         * This happens because polldat_t is still not associated with
         * the pointer to the pollhead_t structure.
         */
        pollhead_insert(*php, pdp);

        /*
         * From now on event notification can be detected in pollwakeup(),
         * Use fop_poll() again to check the current status of the event.
         */
        pdp->pd_php = *php;
        fp = pdp->pd_fp;
        curthread->t_pollcache = (pollcache_t *)pdp->pd_pcache;
        error = fop_poll(fp->f_vnode, pdp->pd_events, 0, revents, php, NULL);
        curthread->t_pollcache = NULL;
        return (error);
}

/*
 * Grow the hash table. Rehash all the elements on the hash table.
 */
static void
port_cache_grow_hashtbl(port_fdcache_t *pcp)
{
        portfd_t        **oldtbl;
        polldat_t       *pdp;
        portfd_t        *pfd;
        polldat_t       *pdp1;
        int             oldsize;
        int             i;

        ASSERT(MUTEX_HELD(&pcp->pc_lock));
        oldsize = pcp->pc_hashsize;
        oldtbl = pcp->pc_hash;
        pcp->pc_hashsize *= PORTHASH_MULT;
        pcp->pc_hash = kmem_zalloc(pcp->pc_hashsize * sizeof (portfd_t *),
            KM_SLEEP);
        /*
         * rehash existing elements
         */
        pcp->pc_fdcount = 0;
        for (i = 0; i < oldsize; i++) {
                pfd = oldtbl[i];
                pdp = PFTOD(pfd);
                while (pdp != NULL) {
                        pdp1 = pdp->pd_hashnext;
                        port_cache_insert_fd(pcp, pdp);
                        pdp = pdp1;
                }
        }
        kmem_free(oldtbl, oldsize * sizeof (portfd_t *));
}
/*
 * This routine inserts a polldat into the portcache's hash table. It
 * may be necessary to grow the size of the hash table.
 */
static void
port_cache_insert_fd(port_fdcache_t *pcp, polldat_t *pdp)
{
        portfd_t        **bucket;

        ASSERT(MUTEX_HELD(&pcp->pc_lock));
        if (pcp->pc_fdcount > (pcp->pc_hashsize * PORTHASH_MULT))
                port_cache_grow_hashtbl(pcp);
        bucket = PORT_FD_BUCKET(pcp, pdp->pd_fd);
        pdp->pd_hashnext = PFTOD(*bucket);
        *bucket = PDTOF(pdp);
        pcp->pc_fdcount++;
}


/*
 * The port_remove_portfd() function dissociates the port from the fd
 * and vive versa.
 */
static void
port_remove_portfd(polldat_t *pdp, port_fdcache_t *pcp)
{
        port_t  *pp;
        file_t  *fp;
        int     fd;

        ASSERT(MUTEX_HELD(&pcp->pc_lock));
        pp = pdp->pd_portev->portkev_port;
        fp = getf(fd = pdp->pd_fd);
        /*
         * If we did not get the fp for pd_fd but its portfd_t
         * still exist in the cache, it means the pd_fd is being
         * closed by some other thread which will also free the portfd_t.
         */
        if (fp != NULL) {
                delfd_port(pdp->pd_fd, PDTOF(pdp));
                (void) port_remove_fd_object(PDTOF(pdp), pp, pcp);
                releasef(fd);
        }
}

/*
 * This function is used by port_close_sourcefd() to destroy the cache
 * on last close.
 */
static void
port_pcache_destroy(port_fdcache_t *pcp)
{
        ASSERT(pcp->pc_fdcount == 0);
        kmem_free(pcp->pc_hash, sizeof (polldat_t *) * pcp->pc_hashsize);
        mutex_destroy(&pcp->pc_lock);
        kmem_free(pcp, sizeof (port_fdcache_t));
}

/*
 * port_close() calls this function to request the PORT_SOURCE_FD source
 * to remove/free all resources allocated and associated with the port.
 */
/* ARGSUSED */
static void
port_close_sourcefd(void *arg, int port, pid_t pid, int lastclose)
{
        port_t          *pp = arg;
        port_fdcache_t  *pcp;
        portfd_t        **hashtbl;
        polldat_t       *pdp;
        polldat_t       *pdpnext;
        int             index;

        pcp = pp->port_queue.portq_pcp;
        if (pcp == NULL)
                /* no cache available -> nothing to do */
                return;

        mutex_enter(&pcp->pc_lock);
        /*
         * Scan the cache and free all allocated portfd_t and port_kevent_t
         * structures.
         */
        hashtbl = pcp->pc_hash;
        for (index = 0; index < pcp->pc_hashsize; index++) {
                for (pdp = PFTOD(hashtbl[index]); pdp != NULL; pdp = pdpnext) {
                        pdpnext = pdp->pd_hashnext;
                        if (pid == pdp->pd_portev->portkev_pid) {
                                /*
                                 * remove polldat + port_event_t from cache
                                 * only when current process did the
                                 * association.
                                 */
                                port_remove_portfd(pdp, pcp);
                        }
                }
        }
        if (lastclose) {
                /*
                 * Wait for all the portfd's to be freed.
                 * The remaining portfd_t's are the once we did not
                 * free in port_remove_portfd since some other thread
                 * is closing the fd. These threads will free the portfd_t's
                 * once we drop the pc_lock mutex.
                 */
                while (pcp->pc_fdcount) {
                        (void) cv_wait_sig(&pcp->pc_lclosecv, &pcp->pc_lock);
                }
                /* event port vnode will be destroyed -> remove everything */
                pp->port_queue.portq_pcp = NULL;
        }
        mutex_exit(&pcp->pc_lock);
        /*
         * last close:
         * pollwakeup() can not further interact with this cache
         * (all polldat structs are removed from pollhead entries).
         */
        if (lastclose)
                port_pcache_destroy(pcp);
}