file: speed up loading non-gzipped modules when zlib is enabled.

Just now realized that my distro (Gentoo) enables support for gzip but
does not compress modules by default.

In this case it's better to have a special case that uses mmap()
instead of a loop of realloc() + gzread().

diff --git a/libkmod/libkmod-file.c b/libkmod/libkmod-file.c
index 13add1286b7622e3f357aa05c470f95603553db4..99ff3f2abe9c10e428de60bfb09c5ea9e46c3aab 100644 (file)
--- a/libkmod/libkmod-file.c
+++ b/libkmod/libkmod-file.c
@@ -37,25 +37,50 @@
 struct kmod_file {
 #ifdef ENABLE_ZLIB
        gzFile gzf;
-#else
-       int fd;
 #endif
+       int fd;
        off_t size;
        void *memory;
 };
 
 #ifdef ENABLE_ZLIB
 #define READ_STEP (4 * 1024 * 1024)
-static int zlip_file_open(struct kmod_file *file, const char *filename)
+
+static bool check_zlib(struct kmod_file *file)
+{
+       uint8_t magic[2] = {0, 0}, zlibmagic[2] = {0x1f, 0x8b};
+       size_t done = 0, todo = 2;
+       while (todo > 0) {
+               ssize_t r = read(file->fd, magic + done, todo);
+               if (r > 0){
+                       todo -= r;
+                       done += r;
+               } else if (r == 0)
+                       goto error;
+               else if (errno == EAGAIN || errno == EINTR)
+                       continue;
+               else
+                       goto error;
+       }
+       lseek(file->fd, 0, SEEK_SET);
+       return memcmp(magic, zlibmagic, 2) == 0;
+error:
+       lseek(file->fd, 0, SEEK_SET);
+       return false;
+}
+
+static int zlib_file_open(struct kmod_file *file)
 {
        int err = 0;
        off_t did = 0, total = 0;
        unsigned char *p = NULL;
 
        errno = 0;
-       file->gzf = gzopen(filename, "rbe");
-       if (file->gzf == NULL)
+       file->gzf = gzdopen(file->fd, "rb");
+       if (file->gzf == NULL) {
+               close(file->fd);
                return -errno;
+       }
 
        for (;;) {
                int r;
@@ -88,16 +113,13 @@ error:
        gzclose(file->gzf);
        return err;
 }
-#else
-static int reg_file_open(struct kmod_file *file, const char *filename)
+#endif
+
+static int reg_file_open(struct kmod_file *file)
 {
        struct stat st;
        int err = 0;
 
-       file->fd = open(filename, O_RDONLY|O_CLOEXEC);
-       if (file->fd < 0)
-               return -errno;
-
        if (fstat(file->fd, &st) < 0) {
                err = -errno;
                goto error;
@@ -115,7 +137,6 @@ error:
        close(file->fd);
        return err;
 }
-#endif
 
 struct kmod_file *kmod_file_open(const char *filename)
 {
@@ -125,12 +146,20 @@ struct kmod_file *kmod_file_open(const char *filename)
        if (file == NULL)
                return NULL;
 
+       file->fd = open(filename, O_RDONLY|O_CLOEXEC);
+       if (file->fd < 0) {
+               err = -errno;
+               goto error;
+       }
+
 #ifdef ENABLE_ZLIB
-       err = zlip_file_open(file, filename);
-#else
-       err = reg_file_open(file, filename);
+       if (check_zlib(file))
+               err = zlib_file_open(file);
+       else
 #endif
+               err = reg_file_open(file);
 
+error:
        if (err < 0) {
                free(file);
                errno = -err;
@@ -153,11 +182,15 @@ off_t kmod_file_get_size(const struct kmod_file *file)
 void kmod_file_unref(struct kmod_file *file)
 {
 #ifdef ENABLE_ZLIB
-       free(file->memory);
-       gzclose(file->gzf);
-#else
-       munmap(file->memory, file->size);
-       close(file->fd);
+       if (file->gzf != NULL) {
+               free(file->memory);
+               gzclose(file->gzf);
+       } else {
+#endif
+               munmap(file->memory, file->size);
+               close(file->fd);
+#ifdef ENABLE_ZLIB
+       }
 #endif
        free(file);
 }