Re: [PATCH] Enable index-pack threading in msysgit.

> This adds a Windows implementation of pread.  Note that it is NOT
> safe to intersperse calls to read() and pread() on a file
> descriptor.  According to the ReadFile spec, using the 'overlapped'
> argument should not affect the implicit position pointer of the
> descriptor.  Experiments have shown that this is, in fact, a lie.

>
> To accomodate that fact, this change also incorporates:
>
> http://article.gmane.org/gmane.comp.version-control.git/196042
>
> ... which gives each index-pack thread its own file descriptor.
> ---
>  builtin/index-pack.c | 21 ++++++++++++++++-----
>  compat/mingw.c       | 31 ++++++++++++++++++++++++++++++-
>  compat/mingw.h       |  3 +++
>  config.mak.uname     |  1 -
>  4 files changed, 49 insertions(+), 7 deletions(-)
>
> diff --git a/builtin/index-pack.c b/builtin/index-pack.c
> index 2f37a38..c02dd4c 100644
> --- a/builtin/index-pack.c
> +++ b/builtin/index-pack.c
> @@ -51,6 +51,7 @@ struct thread_local {
>  #endif
>         struct base_data *base_cache;
>         size_t base_cache_used;
> +       int pack_fd;
>  };
>
>  /*
> @@ -91,7 +92,8 @@ static off_t consumed_bytes;
>  static unsigned deepest_delta;
>  static git_SHA_CTX input_ctx;
>  static uint32_t input_crc32;
> -static int input_fd, output_fd, pack_fd;
> +static const char *curr_pack;
> +static int input_fd, output_fd;
>
>  #ifndef NO_PTHREADS
>
> @@ -134,6 +136,7 @@ static inline void unlock_mutex(pthread_mutex_t *mutex)
>   */
>  static void init_thread(void)
>  {
> +       int i;
>         init_recursive_mutex(&read_mutex);
>         pthread_mutex_init(&counter_mutex, NULL);
>         pthread_mutex_init(&work_mutex, NULL);
> @@ -141,11 +144,17 @@ static void init_thread(void)
>                 pthread_mutex_init(&deepest_delta_mutex, NULL);
>         pthread_key_create(&key, NULL);
>         thread_data = xcalloc(nr_threads, sizeof(*thread_data));
> +       for (i = 0; i < nr_threads; i++) {
> +               thread_data[i].pack_fd = open(curr_pack, O_RDONLY);
> +               if (thread_data[i].pack_fd == -1)
> +                       die_errno("unable to open %s", curr_pack);
> +       }
>         threads_active = 1;
>  }
>
>  static void cleanup_thread(void)
>  {
> +       int i;
>         if (!threads_active)
>                 return;
>         threads_active = 0;
> @@ -155,6 +164,8 @@ static void cleanup_thread(void)
>         if (show_stat)
>                 pthread_mutex_destroy(&deepest_delta_mutex);
>         pthread_key_delete(key);
> +       for (i = 0; i < nr_threads; i++)
> +               close(thread_data[i].pack_fd);
>         free(thread_data);
>  }
>
> @@ -288,13 +299,13 @@ static const char *open_pack_file(const char *pack_name)
>                         output_fd = open(pack_name, O_CREAT|O_EXCL|O_RDWR, 0600);
>                 if (output_fd < 0)
>                         die_errno(_("unable to create '%s'"), pack_name);
> -               pack_fd = output_fd;
> +               nothread_data.pack_fd = output_fd;
>         } else {
>                 input_fd = open(pack_name, O_RDONLY);
>                 if (input_fd < 0)
>                         die_errno(_("cannot open packfile '%s'"), pack_name);
>                 output_fd = -1;
> -               pack_fd = input_fd;
> +               nothread_data.pack_fd = input_fd;
>         }
>         git_SHA1_Init(&input_ctx);
>         return pack_name;
> @@ -542,7 +553,7 @@ static void *unpack_data(struct object_entry *obj,
>
>         do {
>                 ssize_t n = (len < 64*1024) ? len : 64*1024;
> -               n = pread(pack_fd, inbuf, n, from);
> +               n = pread(get_thread_data()->pack_fd, inbuf, n, from);
>                 if (n < 0)
>                         die_errno(_("cannot pread pack file"));
>                 if (!n)
> @@ -1490,7 +1501,7 @@ static void show_pack_info(int stat_only)
>  int cmd_index_pack(int argc, const char **argv, const char *prefix)
>  {
>         int i, fix_thin_pack = 0, verify = 0, stat_only = 0;
> -       const char *curr_pack, *curr_index;
> +       const char *curr_index;
>         const char *index_name = NULL, *pack_name = NULL;
>         const char *keep_name = NULL, *keep_msg = NULL;
>         char *index_name_buf = NULL, *keep_name_buf = NULL;
> diff --git a/compat/mingw.c b/compat/mingw.c
> index 383cafe..6cc85d6 100644
> --- a/compat/mingw.c
> +++ b/compat/mingw.c
> @@ -329,7 +329,36 @@ int mingw_mkdir(const char *path, int mode)
>         return ret;
>  }
>
> -int mingw_open (const char *filename, int oflags, ...)
> +
> +ssize_t mingw_pread(int fd, void *buf, size_t count, off64_t offset)
> +{
> +       HANDLE hand = (HANDLE)_get_osfhandle(fd);
> +       if (hand == INVALID_HANDLE_VALUE) {
> +               errno = EBADF;
> +               return -1;
> +       }
> +
> +       LARGE_INTEGER offset_value;
> +       offset_value.QuadPart = offset;
> +
> +       DWORD bytes_read = 0;
> +       OVERLAPPED overlapped = {0};
> +       overlapped.Offset = offset_value.LowPart;
> +       overlapped.OffsetHigh = offset_value.HighPart;
> +       BOOL result = ReadFile(hand, buf, count, &bytes_read, &overlapped);
> +
> +       ssize_t ret = bytes_read;
> +
> +       if (!result && GetLastError() != ERROR_HANDLE_EOF)
> +       {
> +               errno = err_win_to_posix(GetLastError());
> +               ret = -1;
> +       }
> +
> +       return ret;
> +}
> +
> +int mingw_open(const char *filename, int oflags, ...)
>  {
>         va_list args;
>         unsigned mode;
> diff --git a/compat/mingw.h b/compat/mingw.h
> index 08b83fe..377ba50 100644
> --- a/compat/mingw.h
> +++ b/compat/mingw.h
> @@ -174,6 +174,9 @@ int mingw_unlink(const char *pathname);
>  int mingw_rmdir(const char *path);
>  #define rmdir mingw_rmdir
>
> +ssize_t mingw_pread(int fd, void *buf, size_t count, off64_t offset);
> +#define pread mingw_pread
> +
>  int mingw_open (const char *filename, int oflags, ...);
>  #define open mingw_open
>
> diff --git a/config.mak.uname b/config.mak.uname
> index e8acc39..b405524 100644
> --- a/config.mak.uname
> +++ b/config.mak.uname
> @@ -474,7 +474,6 @@ ifeq ($(uname_S),NONSTOP_KERNEL)
>  endif
>  ifneq (,$(findstring MINGW,$(uname_S)))
>         pathsep = ;
> -       NO_PREAD = YesPlease
>         NEEDS_CRYPTO_WITH_SSL = YesPlease
>         NO_LIBGEN_H = YesPlease
>         NO_POLL = YesPlease
> --
> 1.9.0.279.gdc9e3eb
>
> --
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