Annotation of qemu/linux-aio.c, revision 1.1.1.3

1.1       root        1: /*
                      2:  * Linux native AIO support.
                      3:  *
                      4:  * Copyright (C) 2009 IBM, Corp.
                      5:  * Copyright (C) 2009 Red Hat, Inc.
                      6:  *
                      7:  * This work is licensed under the terms of the GNU GPL, version 2 or later.
                      8:  * See the COPYING file in the top-level directory.
                      9:  */
                     10: #include "qemu-common.h"
                     11: #include "qemu-aio.h"
                     12: #include "block_int.h"
                     13: #include "block/raw-posix-aio.h"
                     14: 
                     15: #include <sys/eventfd.h>
                     16: #include <libaio.h>
                     17: 
                     18: /*
                     19:  * Queue size (per-device).
                     20:  *
                     21:  * XXX: eventually we need to communicate this to the guest and/or make it
                     22:  *      tunable by the guest.  If we get more outstanding requests at a time
                     23:  *      than this we will get EAGAIN from io_submit which is communicated to
                     24:  *      the guest as an I/O error.
                     25:  */
                     26: #define MAX_EVENTS 128
                     27: 
                     28: struct qemu_laiocb {
                     29:     BlockDriverAIOCB common;
                     30:     struct qemu_laio_state *ctx;
                     31:     struct iocb iocb;
                     32:     ssize_t ret;
                     33:     size_t nbytes;
1.1.1.3 ! root       34:     QEMUIOVector *qiov;
        !            35:     bool is_read;
1.1       root       36:     QLIST_ENTRY(qemu_laiocb) node;
                     37: };
                     38: 
                     39: struct qemu_laio_state {
                     40:     io_context_t ctx;
                     41:     int efd;
                     42:     int count;
                     43: };
                     44: 
                     45: static inline ssize_t io_event_ret(struct io_event *ev)
                     46: {
                     47:     return (ssize_t)(((uint64_t)ev->res2 << 32) | ev->res);
                     48: }
                     49: 
                     50: /*
                     51:  * Completes an AIO request (calls the callback and frees the ACB).
                     52:  */
                     53: static void qemu_laio_process_completion(struct qemu_laio_state *s,
                     54:     struct qemu_laiocb *laiocb)
                     55: {
                     56:     int ret;
                     57: 
                     58:     s->count--;
                     59: 
                     60:     ret = laiocb->ret;
                     61:     if (ret != -ECANCELED) {
1.1.1.3 ! root       62:         if (ret == laiocb->nbytes) {
1.1       root       63:             ret = 0;
1.1.1.3 ! root       64:         } else if (ret >= 0) {
        !            65:             /* Short reads mean EOF, pad with zeros. */
        !            66:             if (laiocb->is_read) {
        !            67:                 qemu_iovec_memset_skip(laiocb->qiov, 0,
        !            68:                     laiocb->qiov->size - ret, ret);
        !            69:             } else {
        !            70:                 ret = -EINVAL;
        !            71:             }
        !            72:         }
1.1       root       73: 
                     74:         laiocb->common.cb(laiocb->common.opaque, ret);
                     75:     }
                     76: 
                     77:     qemu_aio_release(laiocb);
                     78: }
                     79: 
                     80: static void qemu_laio_completion_cb(void *opaque)
                     81: {
                     82:     struct qemu_laio_state *s = opaque;
                     83: 
                     84:     while (1) {
                     85:         struct io_event events[MAX_EVENTS];
                     86:         uint64_t val;
                     87:         ssize_t ret;
                     88:         struct timespec ts = { 0 };
                     89:         int nevents, i;
                     90: 
                     91:         do {
                     92:             ret = read(s->efd, &val, sizeof(val));
1.1.1.2   root       93:         } while (ret == -1 && errno == EINTR);
1.1       root       94: 
                     95:         if (ret == -1 && errno == EAGAIN)
                     96:             break;
                     97: 
                     98:         if (ret != 8)
                     99:             break;
                    100: 
                    101:         do {
                    102:             nevents = io_getevents(s->ctx, val, MAX_EVENTS, events, &ts);
                    103:         } while (nevents == -EINTR);
                    104: 
                    105:         for (i = 0; i < nevents; i++) {
                    106:             struct iocb *iocb = events[i].obj;
                    107:             struct qemu_laiocb *laiocb =
                    108:                     container_of(iocb, struct qemu_laiocb, iocb);
                    109: 
                    110:             laiocb->ret = io_event_ret(&events[i]);
1.1.1.3 ! root      111:             qemu_laio_process_completion(s, laiocb);
1.1       root      112:         }
                    113:     }
                    114: }
                    115: 
                    116: static int qemu_laio_flush_cb(void *opaque)
                    117: {
                    118:     struct qemu_laio_state *s = opaque;
                    119: 
                    120:     return (s->count > 0) ? 1 : 0;
                    121: }
                    122: 
                    123: static void laio_cancel(BlockDriverAIOCB *blockacb)
                    124: {
                    125:     struct qemu_laiocb *laiocb = (struct qemu_laiocb *)blockacb;
                    126:     struct io_event event;
                    127:     int ret;
                    128: 
                    129:     if (laiocb->ret != -EINPROGRESS)
                    130:         return;
                    131: 
                    132:     /*
                    133:      * Note that as of Linux 2.6.31 neither the block device code nor any
                    134:      * filesystem implements cancellation of AIO request.
                    135:      * Thus the polling loop below is the normal code path.
                    136:      */
                    137:     ret = io_cancel(laiocb->ctx->ctx, &laiocb->iocb, &event);
                    138:     if (ret == 0) {
                    139:         laiocb->ret = -ECANCELED;
                    140:         return;
                    141:     }
                    142: 
                    143:     /*
                    144:      * We have to wait for the iocb to finish.
                    145:      *
                    146:      * The only way to get the iocb status update is by polling the io context.
                    147:      * We might be able to do this slightly more optimal by removing the
                    148:      * O_NONBLOCK flag.
                    149:      */
                    150:     while (laiocb->ret == -EINPROGRESS)
                    151:         qemu_laio_completion_cb(laiocb->ctx);
                    152: }
                    153: 
                    154: static AIOPool laio_pool = {
                    155:     .aiocb_size         = sizeof(struct qemu_laiocb),
                    156:     .cancel             = laio_cancel,
                    157: };
                    158: 
                    159: BlockDriverAIOCB *laio_submit(BlockDriverState *bs, void *aio_ctx, int fd,
                    160:         int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
                    161:         BlockDriverCompletionFunc *cb, void *opaque, int type)
                    162: {
                    163:     struct qemu_laio_state *s = aio_ctx;
                    164:     struct qemu_laiocb *laiocb;
                    165:     struct iocb *iocbs;
                    166:     off_t offset = sector_num * 512;
                    167: 
                    168:     laiocb = qemu_aio_get(&laio_pool, bs, cb, opaque);
                    169:     if (!laiocb)
                    170:         return NULL;
                    171:     laiocb->nbytes = nb_sectors * 512;
                    172:     laiocb->ctx = s;
                    173:     laiocb->ret = -EINPROGRESS;
1.1.1.3 ! root      174:     laiocb->is_read = (type == QEMU_AIO_READ);
        !           175:     laiocb->qiov = qiov;
1.1       root      176: 
                    177:     iocbs = &laiocb->iocb;
                    178: 
                    179:     switch (type) {
                    180:     case QEMU_AIO_WRITE:
                    181:         io_prep_pwritev(iocbs, fd, qiov->iov, qiov->niov, offset);
                    182:        break;
                    183:     case QEMU_AIO_READ:
                    184:         io_prep_preadv(iocbs, fd, qiov->iov, qiov->niov, offset);
                    185:        break;
1.1.1.3 ! root      186:     /* Currently Linux kernel does not support other operations */
1.1       root      187:     default:
                    188:         fprintf(stderr, "%s: invalid AIO request type 0x%x.\n",
                    189:                         __func__, type);
                    190:         goto out_free_aiocb;
                    191:     }
                    192:     io_set_eventfd(&laiocb->iocb, s->efd);
                    193:     s->count++;
                    194: 
                    195:     if (io_submit(s->ctx, 1, &iocbs) < 0)
                    196:         goto out_dec_count;
                    197:     return &laiocb->common;
                    198: 
                    199: out_dec_count:
                    200:     s->count--;
1.1.1.3 ! root      201: out_free_aiocb:
        !           202:     qemu_aio_release(laiocb);
1.1       root      203:     return NULL;
                    204: }
                    205: 
                    206: void *laio_init(void)
                    207: {
                    208:     struct qemu_laio_state *s;
                    209: 
1.1.1.3 ! root      210:     s = g_malloc0(sizeof(*s));
1.1       root      211:     s->efd = eventfd(0, 0);
                    212:     if (s->efd == -1)
                    213:         goto out_free_state;
                    214:     fcntl(s->efd, F_SETFL, O_NONBLOCK);
                    215: 
                    216:     if (io_setup(MAX_EVENTS, &s->ctx) != 0)
                    217:         goto out_close_efd;
                    218: 
                    219:     qemu_aio_set_fd_handler(s->efd, qemu_laio_completion_cb, NULL,
1.1.1.3 ! root      220:         qemu_laio_flush_cb, NULL, s);
1.1       root      221: 
                    222:     return s;
                    223: 
                    224: out_close_efd:
                    225:     close(s->efd);
                    226: out_free_state:
1.1.1.3 ! root      227:     g_free(s);
1.1       root      228:     return NULL;
                    229: }

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