details: http://hg.nginx.org/nginx/rev/4df3d9fcdee8
branches:
changeset: 6437:4df3d9fcdee8
user: Maxim Dounin <mdounin@mdounin.ru>
date: Tue Mar 15 18:26:17 2016 +0300
description:
Truncation detection in sendfile() on Linux.

This addresses connection hangs as observed in ticket #504, and
CPU hogs with "aio threads; sendfile on" as reported in the mailing list,
see http://mailman.nginx.org/pipermail/nginx-ru/2016-March/057638.html.

The alert is identical to one used on FreeBSD.

diffstat:

src/os/unix/ngx_linux_sendfile_chain.c | 26 ++++++++++++++++++++++++++
1 files changed, 26 insertions(+), 0 deletions(-)

diffs (43 lines):

diff --git a/src/os/unix/ngx_linux_sendfile_chain.c b/src/os/unix/ngx_linux_sendfile_chain.c
--- a/src/os/unix/ngx_linux_sendfile_chain.c
+++ b/src/os/unix/ngx_linux_sendfile_chain.c
@@ -292,6 +292,19 @@ eintr:
}
}

+ if (n == 0) {
+ /*
+ * if sendfile returns zero, then someone has truncated the file,
+ * so the offset became beyond the end of the file
+ */
+
+ ngx_log_error(NGX_LOG_ALERT, c->log, 0,
+ "sendfile() reported that \"%s\" was truncated at %O",
+ file->file->name.data, file->file_pos);
+
+ return NGX_ERROR;
+ }
+
ngx_log_debug3(NGX_LOG_DEBUG_EVENT, c->log, 0, "sendfile: %z of %uz @%O",
n, size, file->file_pos);

@@ -354,6 +367,19 @@ ngx_linux_sendfile_thread(ngx_connection
return NGX_ERROR;
}

+ if (ctx->sent == 0) {
+ /*
+ * if sendfile returns zero, then someone has truncated the file,
+ * so the offset became beyond the end of the file
+ */
+
+ ngx_log_error(NGX_LOG_ALERT, c->log, 0,
+ "sendfile() reported that \"%s\" was truncated at %O",
+ file->file->name.data, file->file_pos);
+
+ return NGX_ERROR;
+ }
+
*sent = ctx->sent;

return (ctx->sent == ctx->size) ? NGX_DONE : NGX_AGAIN;

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