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authorLukas Larsson <[email protected]>2017-09-27 14:32:12 +0200
committerLukas Larsson <[email protected]>2017-09-27 14:32:12 +0200
commitb649f1a1865179a4cfe3a85a468ad7c799dc88cb (patch)
tree504bd2bfe80cbb3a2d8b0dc1c3331011366f1784
parent25587f05f5d80f9cfa25df953b3ce7f53c70d31a (diff)
parentc9515d7a93b57ed43c16fd88eb5892e270935814 (diff)
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Merge branch 'kvakvs/zero-size-read_file/ERL-327/PR-1524/OTP-14637'
* kvakvs/zero-size-read_file/ERL-327/PR-1524/OTP-14637: erts: On zero-size files attempt to read until EOF
-rw-r--r--erts/emulator/drivers/common/efile_drv.c61
-rw-r--r--erts/emulator/test/efile_SUITE.erl49
2 files changed, 105 insertions, 5 deletions
diff --git a/erts/emulator/drivers/common/efile_drv.c b/erts/emulator/drivers/common/efile_drv.c
index a1b15a2199..4e1d2f0d7f 100644
--- a/erts/emulator/drivers/common/efile_drv.c
+++ b/erts/emulator/drivers/common/efile_drv.c
@@ -1261,6 +1261,50 @@ static void free_read_line(void *data)
EF_FREE(d);
}
+void read_file_zero_size(struct t_data* d);
+#define ZERO_FILE_CHUNK (64 * 1024)
+
+/* [ERL-327] Some special files like /proc/... have reported size 0 */
+void read_file_zero_size(struct t_data* d) {
+ size_t total_read_size = 0;
+ size_t allocated_size = ZERO_FILE_CHUNK; /* allocd in invoke_read_file */
+ for (;;) {
+ size_t read_result;
+
+ /* Read until we hit EOF (read less than FILE_SEGMENT_READ) */
+ d->result_ok = efile_read(&d->errInfo,
+ EFILE_MODE_READ,
+ (int) d->fd,
+ (d->c.read_file.binp->orig_bytes +
+ total_read_size),
+ ZERO_FILE_CHUNK,
+ &read_result);
+ if (!d->result_ok) {
+ break;
+ }
+
+ total_read_size += read_result;
+ d->c.read_file.offset += read_result;
+ if (read_result < ZERO_FILE_CHUNK) {
+ break;
+ }
+
+ /* Grow before the next read call */
+ allocated_size = total_read_size + ZERO_FILE_CHUNK;
+ d->c.read_file.binp = driver_realloc_binary(d->c.read_file.binp,
+ allocated_size);
+ }
+
+ /* Finalize the memory usage. Hopefully it was read fully on the first
+ * go, so the binary allocation overhead becomes:
+ * alloc ZERO_FILE_CHUNK (64kb) -> realloc real_size */
+ if (allocated_size != total_read_size) {
+ d->c.read_file.binp = driver_realloc_binary(d->c.read_file.binp,
+ total_read_size);
+ }
+ d->again = 0;
+}
+
static void invoke_read_file(void *data)
{
struct t_data *d = (struct t_data *) data;
@@ -1279,9 +1323,15 @@ static void invoke_read_file(void *data)
}
d->fd = fd;
d->c.read_file.size = (int) size;
- if (size < 0 || size != d->c.read_file.size ||
- ! (d->c.read_file.binp =
- driver_alloc_binary(d->c.read_file.size))) {
+
+ /* For zero sized files allocate a reasonable chunk to attempt reading
+ * anyway. Note: This will eat ZERO_FILE_CHUNK bytes for any 0 file
+ * and free them immediately after (if the file was empty). */
+ ERTS_ASSERT(size >= 0);
+ d->c.read_file.binp = driver_alloc_binary(size != 0 ? (size_t)size
+ : ZERO_FILE_CHUNK);
+
+ if (size < 0 || size != d->c.read_file.size || !d->c.read_file.binp) {
d->result_ok = 0;
d->errInfo.posix_errno = ENOMEM;
goto close;
@@ -1290,6 +1340,11 @@ static void invoke_read_file(void *data)
}
/* Invariant: d->c.read_file.size >= d->c.read_file.offset */
+ if (d->c.read_file.size == 0) {
+ read_file_zero_size(d);
+ goto close;
+ }
+
read_size = (size_t) (d->c.read_file.size - d->c.read_file.offset);
if (! read_size) goto close;
chop = d->again && read_size >= FILE_SEGMENT_READ*2;
diff --git a/erts/emulator/test/efile_SUITE.erl b/erts/emulator/test/efile_SUITE.erl
index f0e1bcf04b..08d5597d78 100644
--- a/erts/emulator/test/efile_SUITE.erl
+++ b/erts/emulator/test/efile_SUITE.erl
@@ -19,16 +19,20 @@
-module(efile_SUITE).
-export([all/0, suite/0]).
--export([iter_max_files/1, async_dist/1]).
+-export([async_dist/1,
+ iter_max_files/1,
+ proc_zero_sized_files/1
+ ]).
-export([do_iter_max_files/2, do_async_dist/1]).
-include_lib("common_test/include/ct.hrl").
+-include_lib("stdlib/include/assert.hrl").
suite() -> [{ct_hooks,[ts_install_cth]}].
all() ->
- [iter_max_files, async_dist].
+ [iter_max_files, async_dist, proc_zero_sized_files].
do_async_dist(Dir) ->
X = 100,
@@ -162,3 +166,44 @@ open_files(Name) ->
% io:format("Error reason: ~p", [_Reason]),
[]
end.
+
+%% @doc If /proc filesystem exists (no way to know if it is real proc or just
+%% a /proc directory), let's read some zero sized files 500 times each, while
+%% ensuring that response isn't empty << >>
+proc_zero_sized_files(Config) when is_list(Config) ->
+ {Type, Flavor} = os:type(),
+ %% Some files which exist on Linux but might be missing on other systems
+ Inputs = ["/proc/cpuinfo",
+ "/proc/meminfo",
+ "/proc/partitions",
+ "/proc/swaps",
+ "/proc/version",
+ "/proc/uptime",
+ %% curproc is present on freebsd
+ "/proc/curproc/cmdline"],
+ case filelib:is_dir("/proc") of
+ false -> {skip, "/proc not found"}; % skip the test if no /proc
+ _ when Type =:= unix andalso Flavor =:= sunos ->
+ %% SunOS has a /proc, but no zero sized special files
+ {skip, "sunos does not have any zero sized special files"};
+ true ->
+ %% Take away files which do not exist in proc
+ Inputs1 = lists:filter(fun filelib:is_file/1, Inputs),
+
+ %% Fail if none of mentioned files exist in /proc, did we just get
+ %% a normal /proc directory without any special files?
+ ?assertNotEqual([], Inputs1),
+
+ %% For 6 inputs and 500 attempts each this do run anywhere
+ %% between 500 and 3000 function calls.
+ lists:foreach(
+ fun(Filename) -> do_proc_zero_sized(Filename, 500) end,
+ Inputs1)
+ end.
+
+%% @doc Test one file N times to also trigger possible leaking fds and memory
+do_proc_zero_sized(_Filename, 0) -> ok;
+do_proc_zero_sized(Filename, N) ->
+ Data = file:read_file(Filename),
+ ?assertNotEqual(<<>>, Data),
+ do_proc_zero_sized(Filename, N-1).