[v2,2/9] linux: Simplify opendir buffer allocation
Commit Message
The fallback allocation is removed, so the possible size constraint
should be analyzed just once; __alloc_dir assumes that 'statp'
argument is non-null, and the max_buffer_size move to close its
used.
Checked on x86_64-linux-gnu and i686-linux-gnu.
---
include/dirent.h | 3 +-
sysdeps/unix/sysv/linux/opendir.c | 51 +++++++++++--------------------
2 files changed, 20 insertions(+), 34 deletions(-)
Comments
* Adhemerval Zanella via Libc-alpha:
> The fallback allocation is removed, so the possible size constraint
> should be analyzed just once; __alloc_dir assumes that 'statp'
> argument is non-null, and the max_buffer_size move to close its
> used.
>
> Checked on x86_64-linux-gnu and i686-linux-gnu.
Looks okay to me. Thanks.
Florian
@@ -48,7 +48,8 @@ extern int __versionsort64 (const struct dirent64 **a,
const struct dirent64 **b)
__attribute_pure__;
extern DIR *__alloc_dir (int fd, bool close_fd, int flags,
- const struct stat64 *statp) attribute_hidden;
+ const struct stat64 *statp)
+ __nonnull (4) attribute_hidden;
extern __typeof (rewinddir) __rewinddir;
extern __typeof (seekdir) __seekdir;
extern __typeof (dirfd) __dirfd;
@@ -23,12 +23,6 @@
#include <not-cancel.h>
-/* The st_blksize value of the directory is used as a hint for the
- size of the buffer which receives struct dirent values from the
- kernel. st_blksize is limited to MAX_DIR_BUFFER_SIZE, in case the
- file system provides a bogus value. */
-#define MAX_DIR_BUFFER_SIZE 1048576U
-
enum {
opendir_oflags = O_RDONLY|O_NDELAY|O_DIRECTORY|O_LARGEFILE|O_CLOEXEC
};
@@ -100,38 +94,29 @@ __alloc_dir (int fd, bool close_fd, int flags, const struct stat64 *statp)
file descriptor. */
if (!close_fd
&& __glibc_unlikely (__fcntl64_nocancel (fd, F_SETFD, FD_CLOEXEC) < 0))
- goto lose;
-
- const size_t default_allocation = (4 * BUFSIZ < sizeof (struct dirent64)
- ? sizeof (struct dirent64) : 4 * BUFSIZ);
- const size_t small_allocation = (BUFSIZ < sizeof (struct dirent64)
- ? sizeof (struct dirent64) : BUFSIZ);
- size_t allocation = default_allocation;
-#ifdef _STATBUF_ST_BLKSIZE
+ return NULL;
+
+ /* The st_blksize value of the directory is used as a hint for the
+ size of the buffer which receives struct dirent values from the
+ kernel. st_blksize is limited to max_buffer_size, in case the
+ file system provides a bogus value. */
+ enum { max_buffer_size = 1048576 };
+
+ const size_t allocation_size = 32768;
+ _Static_assert (allocation_size >= sizeof (struct dirent64),
+ "allocation_size < sizeof (struct dirent64)");
+
/* Increase allocation if requested, but not if the value appears to
- be bogus. */
- if (statp != NULL)
- allocation = MIN (MAX ((size_t) statp->st_blksize, default_allocation),
- MAX_DIR_BUFFER_SIZE);
-#endif
+ be bogus. It will be between 32Kb and 1Mb. */
+ size_t allocation = MIN (MAX ((size_t) statp->st_blksize, allocation_size),
+ max_buffer_size);
DIR *dirp = (DIR *) malloc (sizeof (DIR) + allocation);
if (dirp == NULL)
{
- allocation = small_allocation;
- dirp = (DIR *) malloc (sizeof (DIR) + allocation);
-
- if (dirp == NULL)
- lose:
- {
- if (close_fd)
- {
- int save_errno = errno;
- __close_nocancel_nostatus (fd);
- __set_errno (save_errno);
- }
- return NULL;
- }
+ if (close_fd)
+ __close_nocancel_nostatus (fd);
+ return NULL;
}
dirp->fd = fd;