view src/os/unix/ngx_file_aio_read.c @ 6949:ff0c8e11edbc

Simplified and improved sendfile() code on Linux. The ngx_linux_sendfile() function is now used for both normal sendfile() and sendfile in threads. The ngx_linux_sendfile_thread() function was modified to use the same interface as ngx_linux_sendfile(), and is simply called from ngx_linux_sendfile() when threads are enabled. Special return code NGX_DONE is used to indicate that a thread task was posted and no further actions are needed. If number of bytes sent is less that what we were sending, we now always retry sending. This is needed for sendfile() in threads as the number of bytes we are sending might have been changed since the thread task was posted. And this is also needed for Linux 4.3+, as sendfile() might be interrupted at any time and provides no indication if it was interrupted or not (ticket #1174).
author Maxim Dounin <mdounin@mdounin.ru>
date Tue, 28 Mar 2017 18:15:39 +0300
parents f01ab2dbcfdc
children 7f035fd1ec7b
line wrap: on
line source


/*
 * Copyright (C) Igor Sysoev
 * Copyright (C) Nginx, Inc.
 */


#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_event.h>


/*
 * FreeBSD file AIO features and quirks:
 *
 *    if an asked data are already in VM cache, then aio_error() returns 0,
 *    and the data are already copied in buffer;
 *
 *    aio_read() preread in VM cache as minimum 16K (probably BKVASIZE);
 *    the first AIO preload may be up to 128K;
 *
 *    aio_read/aio_error() may return EINPROGRESS for just written data;
 *
 *    kqueue EVFILT_AIO filter is level triggered only: an event repeats
 *    until aio_return() will be called;
 *
 *    aio_cancel() cannot cancel file AIO: it returns AIO_NOTCANCELED always.
 */


extern int  ngx_kqueue;


static ssize_t ngx_file_aio_result(ngx_file_t *file, ngx_event_aio_t *aio,
    ngx_event_t *ev);
static void ngx_file_aio_event_handler(ngx_event_t *ev);


ngx_int_t
ngx_file_aio_init(ngx_file_t *file, ngx_pool_t *pool)
{
    ngx_event_aio_t  *aio;

    aio = ngx_pcalloc(pool, sizeof(ngx_event_aio_t));
    if (aio == NULL) {
        return NGX_ERROR;
    }

    aio->file = file;
    aio->fd = file->fd;
    aio->event.data = aio;
    aio->event.ready = 1;
    aio->event.log = file->log;

    file->aio = aio;

    return NGX_OK;
}


ssize_t
ngx_file_aio_read(ngx_file_t *file, u_char *buf, size_t size, off_t offset,
    ngx_pool_t *pool)
{
    int               n;
    ngx_event_t      *ev;
    ngx_event_aio_t  *aio;

    if (!ngx_file_aio) {
        return ngx_read_file(file, buf, size, offset);
    }

    if (file->aio == NULL && ngx_file_aio_init(file, pool) != NGX_OK) {
        return NGX_ERROR;
    }

    aio = file->aio;
    ev = &aio->event;

    if (!ev->ready) {
        ngx_log_error(NGX_LOG_ALERT, file->log, 0,
                      "second aio post for \"%V\"", &file->name);
        return NGX_AGAIN;
    }

    ngx_log_debug4(NGX_LOG_DEBUG_CORE, file->log, 0,
                   "aio complete:%d @%O:%uz %V",
                   ev->complete, offset, size, &file->name);

    if (ev->complete) {
        ev->complete = 0;
        ngx_set_errno(aio->err);

        if (aio->err == 0) {
            return aio->nbytes;
        }

        ngx_log_error(NGX_LOG_CRIT, file->log, ngx_errno,
                      "aio read \"%s\" failed", file->name.data);

        return NGX_ERROR;
    }

    ngx_memzero(&aio->aiocb, sizeof(struct aiocb));

    aio->aiocb.aio_fildes = file->fd;
    aio->aiocb.aio_offset = offset;
    aio->aiocb.aio_buf = buf;
    aio->aiocb.aio_nbytes = size;
#if (NGX_HAVE_KQUEUE)
    aio->aiocb.aio_sigevent.sigev_notify_kqueue = ngx_kqueue;
    aio->aiocb.aio_sigevent.sigev_notify = SIGEV_KEVENT;
    aio->aiocb.aio_sigevent.sigev_value.sigval_ptr = ev;
#endif
    ev->handler = ngx_file_aio_event_handler;

    n = aio_read(&aio->aiocb);

    if (n == -1) {
        n = ngx_errno;

        if (n == NGX_EAGAIN) {
            return ngx_read_file(file, buf, size, offset);
        }

        ngx_log_error(NGX_LOG_CRIT, file->log, n,
                      "aio_read(\"%V\") failed", &file->name);

        if (n == NGX_ENOSYS) {
            ngx_file_aio = 0;
            return ngx_read_file(file, buf, size, offset);
        }

        return NGX_ERROR;
    }

    ngx_log_debug2(NGX_LOG_DEBUG_CORE, file->log, 0,
                   "aio_read: fd:%d %d", file->fd, n);

    ev->active = 1;
    ev->ready = 0;
    ev->complete = 0;

    return ngx_file_aio_result(aio->file, aio, ev);
}


static ssize_t
ngx_file_aio_result(ngx_file_t *file, ngx_event_aio_t *aio, ngx_event_t *ev)
{
    int        n;
    ngx_err_t  err;

    n = aio_error(&aio->aiocb);

    ngx_log_debug2(NGX_LOG_DEBUG_CORE, file->log, 0,
                   "aio_error: fd:%d %d", file->fd, n);

    if (n == -1) {
        err = ngx_errno;
        aio->err = err;

        ngx_log_error(NGX_LOG_ALERT, file->log, err,
                      "aio_error(\"%V\") failed", &file->name);
        return NGX_ERROR;
    }

    if (n == NGX_EINPROGRESS) {
        if (ev->ready) {
            ev->ready = 0;
            ngx_log_error(NGX_LOG_ALERT, file->log, n,
                          "aio_read(\"%V\") still in progress",
                          &file->name);
        }

        return NGX_AGAIN;
    }

    n = aio_return(&aio->aiocb);

    if (n == -1) {
        err = ngx_errno;
        aio->err = err;
        ev->ready = 1;

        ngx_log_error(NGX_LOG_CRIT, file->log, err,
                      "aio_return(\"%V\") failed", &file->name);
        return NGX_ERROR;
    }

    aio->err = 0;
    aio->nbytes = n;
    ev->ready = 1;
    ev->active = 0;

    ngx_log_debug2(NGX_LOG_DEBUG_CORE, file->log, 0,
                   "aio_return: fd:%d %d", file->fd, n);

    return n;
}


static void
ngx_file_aio_event_handler(ngx_event_t *ev)
{
    ngx_event_aio_t  *aio;

    aio = ev->data;

    ngx_log_debug2(NGX_LOG_DEBUG_CORE, ev->log, 0,
                   "aio event handler fd:%d %V", aio->fd, &aio->file->name);

    if (ngx_file_aio_result(aio->file, aio, ev) != NGX_AGAIN) {
        aio->handler(ev);
    }
}