Mercurial > hg > nginx
view src/os/unix/ngx_aio_write_chain.c @ 5356:acd51b0f6fd4
Disable symlinks: use O_PATH to open path components.
It was introduced in Linux 2.6.39, glibc 2.14 and allows to obtain
file descriptors without actually opening files. Thus made it possible
to traverse path with openat() syscalls without the need to have read
permissions for path components. It is effectively emulates O_SEARCH
which is missing on Linux.
O_PATH is used in combination with O_RDONLY. The last one is ignored
if O_PATH is used, but it allows nginx to not fail when it was built on
modern system (i.e. glibc 2.14+) and run with a kernel older than 2.6.39.
Then O_PATH is unknown to the kernel and ignored, while O_RDONLY is used.
Sadly, fstat() is not working with O_PATH descriptors till Linux 3.6.
As a workaround we fallback to fstatat() with the AT_EMPTY_PATH flag
that was introduced at the same time as O_PATH.
author | Valentin Bartenev <vbart@nginx.com> |
---|---|
date | Mon, 02 Sep 2013 08:07:59 +0400 |
parents | d620f497c50f |
children |
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/* * Copyright (C) Igor Sysoev * Copyright (C) Nginx, Inc. */ #include <ngx_config.h> #include <ngx_core.h> #include <ngx_event.h> ngx_chain_t * ngx_aio_write_chain(ngx_connection_t *c, ngx_chain_t *in, off_t limit) { u_char *buf, *prev; off_t send, sent; size_t len; ssize_t n, size; ngx_chain_t *cl; /* the maximum limit size is the maximum size_t value - the page size */ if (limit == 0 || limit > (off_t) (NGX_MAX_SIZE_T_VALUE - ngx_pagesize)) { limit = NGX_MAX_SIZE_T_VALUE - ngx_pagesize; } send = 0; sent = 0; cl = in; while (cl) { if (cl->buf->pos == cl->buf->last) { cl = cl->next; continue; } /* we can post the single aio operation only */ if (!c->write->ready) { return cl; } buf = cl->buf->pos; prev = buf; len = 0; /* coalesce the neighbouring bufs */ while (cl && prev == cl->buf->pos && send < limit) { if (ngx_buf_special(cl->buf)) { continue; } size = cl->buf->last - cl->buf->pos; if (send + size > limit) { size = limit - send; } len += size; prev = cl->buf->pos + size; send += size; cl = cl->next; } n = ngx_aio_write(c, buf, len); ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, 0, "aio_write: %z", n); if (n == NGX_ERROR) { return NGX_CHAIN_ERROR; } if (n > 0) { sent += n; c->sent += n; } ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, 0, "aio_write sent: %O", c->sent); for (cl = in; cl; cl = cl->next) { if (sent >= cl->buf->last - cl->buf->pos) { sent -= cl->buf->last - cl->buf->pos; cl->buf->pos = cl->buf->last; continue; } cl->buf->pos += sent; break; } } return cl; }