Threads: offloading of temp files writing to thread pools.

The ngx_thread_write_chain_to_file() function introduced, which
uses ngx_file_t thread_handler, thread_ctx and thread_task fields.
The task context structure (ngx_thread_file_ctx_t) is the same for
both reading and writing, and can be safely shared as long as
operations are serialized.

The task->handler field is now always set (and not only when task is
allocated), as the same task can be used with different handlers.

The thread_write flag is introduced in the ngx_temp_file_t structure
to explicitly enable use of ngx_thread_write_chain_to_file() in
ngx_write_chain_to_temp_file() when supported by caller.

In collaboration with Valentin Bartenev.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/os/unix/ngx_files.h b/src/os/unix/ngx_files.h
index 88b2f81cc..07872b138 100644
--- a/src/os/unix/ngx_files.h
+++ b/src/os/unix/ngx_files.h
@@ -387,6 +387,8 @@ extern ngx_uint_t  ngx_file_aio;
 #if (NGX_THREADS)
 ssize_t ngx_thread_read(ngx_file_t *file, u_char *buf, size_t size,
     off_t offset, ngx_pool_t *pool);
+ssize_t ngx_thread_write_chain_to_file(ngx_file_t *file, ngx_chain_t *cl,
+    off_t offset, ngx_pool_t *pool);
 #endif