On Fri, Oct 30, 2015 at 01:56:03PM +0800, Xiao Guangrong wrote:
> Currently, file_ram_alloc() only works on directory - it creates a file
> under @path and do mmap on it
>
> This patch tries to allow it to work on file directly, if @path is a
> directory it works as before, otherwise it treats @path as the target
> file then directly allocate memory from it
>
> Signed-off-by: Xiao Guangrong <guangrong.xiao@xxxxxxxxxxxxxxx>
> ---
> exec.c | 80 ++++++++++++++++++++++++++++++++++++++++++------------------------
> 1 file changed, 51 insertions(+), 29 deletions(-)
>
> diff --git a/exec.c b/exec.c
> index 3ca7e50..f219010 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -1174,14 +1174,60 @@ void qemu_mutex_unlock_ramlist(void)
> }
>
> #ifdef __linux__
> +static bool path_is_dir(const char *path)
> +{
> + struct stat fs;
> +
> + return stat(path, &fs) == 0 && S_ISDIR(fs.st_mode);
This means file doesn't exist is treated as a file.
Can't figure out if that's intentional, should
be documented in any case.
> +}
> +
> +static int open_file_path(RAMBlock *block, const char *path, size_t size)
> +{
> + char *filename;
> + char *sanitized_name;
> + char *c;
> + int fd;
> +
> + if (!path_is_dir(path)) {
> + int flags = (block->flags & RAM_SHARED) ? O_RDWR : O_RDONLY;
Why does this make sense?
> +
> + flags |= O_EXCL;
And why does this makes sense?
> + return open(path, flags);
> + }
> +
> + /* Make name safe to use with mkstemp by replacing '/' with '_'. */
> + sanitized_name = g_strdup(memory_region_name(block->mr));
> + for (c = sanitized_name; *c != '\0'; c++) {
> + if (*c == '/') {
> + *c = '_';
> + }
> + }
> + filename = g_strdup_printf("%s/qemu_back_mem.%s.XXXXXX", path,
> + sanitized_name);
> + g_free(sanitized_name);
> + fd = mkstemp(filename);
> + if (fd >= 0) {
> + unlink(filename);
> + /*
> + * ftruncate is not supported by hugetlbfs in older
> + * hosts, so don't bother bailing out on errors.
> + * If anything goes wrong with it under other filesystems,
> + * mmap will fail.
> + */
> + if (ftruncate(fd, size)) {
> + perror("ftruncate");
> + }
> + }
> + g_free(filename);
> +
> + return fd;
> +}
> +
> static void *file_ram_alloc(RAMBlock *block,
> ram_addr_t memory,
> const char *path,
> Error **errp)
> {
> - char *filename;
> - char *sanitized_name;
> - char *c;
> void *area;
> int fd;
> uint64_t pagesize;
> @@ -1211,38 +1257,14 @@ static void *file_ram_alloc(RAMBlock *block,
> goto error;
> }
>
> - /* Make name safe to use with mkstemp by replacing '/' with '_'. */
> - sanitized_name = g_strdup(memory_region_name(block->mr));
> - for (c = sanitized_name; *c != '\0'; c++) {
> - if (*c == '/')
> - *c = '_';
> - }
> -
> - filename = g_strdup_printf("%s/qemu_back_mem.%s.XXXXXX", path,
> - sanitized_name);
> - g_free(sanitized_name);
> + memory = ROUND_UP(memory, pagesize);
>
> - fd = mkstemp(filename);
> + fd = open_file_path(block, path, memory);
> if (fd < 0) {
> error_setg_errno(errp, errno,
> "unable to create backing store for path %s", path);
> - g_free(filename);
> goto error;
> }
> - unlink(filename);
> - g_free(filename);
> -
> - memory = ROUND_UP(memory, pagesize);
> -
> - /*
> - * ftruncate is not supported by hugetlbfs in older
> - * hosts, so don't bother bailing out on errors.
> - * If anything goes wrong with it under other filesystems,
> - * mmap will fail.
> - */
> - if (ftruncate(fd, memory)) {
> - perror("ftruncate");
> - }
>
> area = qemu_ram_mmap(fd, memory, pagesize, block->flags & RAM_SHARED);
> if (area == MAP_FAILED) {
> --
> 1.8.3.1
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