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Merge branch 'jc/max-io-size-and-ssize-max' 

Our default I/O size (8 MiB) for large files was too large for some
platforms with smaller SSIZE_MAX, leading to read(2)/write(2)
failures.

* jc/max-io-size-and-ssize-max:
  xread/xwrite: clip MAX_IO_SIZE to SSIZE_MAX
This commit is contained in:
Junio C Hamano 2015-02-25 15:40:13 -08:00
parent 90eea883fd a983e6ac58
commit 81a535da88
1 changed files with 15 additions and 1 deletions
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16
wrapper.c
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@ -172,8 +172,22 @@ void *xcalloc(size_t nmemb, size_t size)
* 64-bit is buggy, returning EINVAL if len >= INT_MAX; and even in
* the absence 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()