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authorLukas Larsson <[email protected]>2014-01-27 12:01:45 +0100
committerLukas Larsson <[email protected]>2014-01-27 14:48:50 +0100
commit0b36ce01e81744f4c0b41bfe1f62b4bf5d0ece97 (patch)
treeef403bfcfc33a41edb54309319a4cf39ca81ecab /erts/preloaded/src/prim_file.erl
parent045fcfc02ace59d07618f8983809236642bba630 (diff)
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erts/kernel: sendfile no longer uses async threads
This has been done because a slow client attack is possible if the async thread pool is used. The scenario is: Client does a request for a file and then slowly receives the file one byte at a time. This will eventually fill the async thread pool with blocking sendfile operations and thus starving the vm of all file operations. If you still want to use the async threads pool for sendfile an option to enable it has been introduced.
Diffstat (limited to 'erts/preloaded/src/prim_file.erl')
-rw-r--r--erts/preloaded/src/prim_file.erl17
1 files changed, 14 insertions, 3 deletions
diff --git a/erts/preloaded/src/prim_file.erl b/erts/preloaded/src/prim_file.erl
index 5999e98340..34679404a2 100644
--- a/erts/preloaded/src/prim_file.erl
+++ b/erts/preloaded/src/prim_file.erl
@@ -27,7 +27,7 @@
%% Generic file contents operations
-export([open/2, close/1, datasync/1, sync/1, advise/4, position/2, truncate/1,
write/2, pwrite/2, pwrite/3, read/2, read_line/1, pread/2, pread/3,
- copy/3, sendfile/10, allocate/3]).
+ copy/3, sendfile/8, allocate/3]).
%% Specialized file operations
-export([open/1, open/3]).
@@ -149,6 +149,9 @@
-define(POSIX_FADV_DONTNEED, 4).
-define(POSIX_FADV_NOREUSE, 5).
+%% Sendfile flags
+-define(EFILE_SENDFILE_USE_THREADS, 1).
+
%%% BIFs
@@ -582,13 +585,14 @@ write_file(_, _) ->
% {error, enotsup};
sendfile(#file_descriptor{module = ?MODULE, data = {Port, _}},
Dest, Offset, Bytes, _ChunkSize, Headers, Trailers,
- _Nodiskio, _MNowait, _Sync) ->
+ Flags) ->
case erlang:port_get_data(Dest) of
Data when Data == inet_tcp; Data == inet6_tcp ->
ok = inet:lock_socket(Dest,true),
{ok, DestFD} = prim_inet:getfd(Dest),
+ IntFlags = translate_sendfile_flags(Flags),
try drv_command(Port, [<<?FILE_SENDFILE, DestFD:32,
- 0:8,
+ IntFlags:8,
Offset:64/unsigned,
Bytes:64/unsigned,
(iolist_size(Headers)):32/unsigned,
@@ -601,6 +605,13 @@ sendfile(#file_descriptor{module = ?MODULE, data = {Port, _}},
{error,badarg}
end.
+translate_sendfile_flags([{use_threads,true}|T]) ->
+ ?EFILE_SENDFILE_USE_THREADS bor translate_sendfile_flags(T);
+translate_sendfile_flags([_|T]) ->
+ translate_sendfile_flags(T);
+translate_sendfile_flags([]) ->
+ 0.
+
%%%-----------------------------------------------------------------
%%% Functions operating on files without handle to the file. ?DRV.