diff options
author | Junio C Hamano <gitster@pobox.com> | 2015-02-12 00:13:10 +0300 |
---|---|---|
committer | Junio C Hamano <gitster@pobox.com> | 2015-02-12 22:01:11 +0300 |
commit | a983e6ac58094a3b2466ad3be13049ce213f9fc3 (patch) | |
tree | 4b63b2088ba8dfacdda37abea41621e26bdf3c37 | |
parent | 0b6806b9e45c659d25b87fb5713c920a3081eac8 (diff) |
xread/xwrite: clip MAX_IO_SIZE to SSIZE_MAX
Since 0b6806b9 (xread, xwrite: limit size of IO to 8MB, 2013-08-20),
we chomp our calls to read(2) and write(2) into chunks of
MAX_IO_SIZE bytes (8 MiB), because a large IO results in a bad
latency when the program needs to be killed. This also brought our
IO below SSIZE_MAX, which is a limit POSIX allows read(2) and
write(2) to fail when the IO size exceeds it, for OS X, where a
problem was originally reported.
However, there are other systems that define SSIZE_MAX smaller than
our default, and feeding 8 MiB to underlying read(2)/write(2) would
fail. Make sure we clip our calls to the lower limit as well.
Reported-by: Joachim Schmitz <jojo@schmitz-digital.de>
Helped-by: Torsten Bögershausen <tboegi@web.de>
Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
-rw-r--r-- | wrapper.c | 16 |
1 files changed, 15 insertions, 1 deletions
@@ -135,8 +135,22 @@ void *xcalloc(size_t nmemb, size_t size) * 64-bit is buggy, returning EINVAL if len >= INT_MAX; and even in * the absense of bugs, large chunks can result in bad latencies when * you decide to kill the process. + * + * We pick 8 MiB as our default, but if the platform defines SSIZE_MAX + * that is smaller than that, clip it to SSIZE_MAX, as a call to + * read(2) or write(2) larger than that is allowed to fail. As the last + * resort, we allow a port to pass via CFLAGS e.g. "-DMAX_IO_SIZE=value" + * to override this, if the definition of SSIZE_MAX given by the platform + * is broken. */ -#define MAX_IO_SIZE (8*1024*1024) +#ifndef MAX_IO_SIZE +# define MAX_IO_SIZE_DEFAULT (8*1024*1024) +# if defined(SSIZE_MAX) && (SSIZE_MAX < MAX_IO_SIZE_DEFAULT) +# define MAX_IO_SIZE SSIZE_MAX +# else +# define MAX_IO_SIZE MAX_IO_SIZE_DEFAULT +# endif +#endif /* * xread() is the same a read(), but it automatically restarts read() |