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linux: Simplify opendir buffer allocation

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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.
This commit is contained in:
Adhemerval Zanella 2020-04-12 17:42:35 -03:00
parent 905ae44c77
commit 4b962c9e85
2 changed files with 19 additions and 33 deletions
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3
include/dirent.h
View File

@ -48,7 +48,8 @@ extern int __versionsort64 (const struct dirent64 **a,
const struct dirent64 **b) const struct dirent64 **b)
__attribute_pure__; __attribute_pure__;
extern DIR *__alloc_dir (int fd, bool close_fd, int flags, 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 (rewinddir) __rewinddir;
extern __typeof (seekdir) __seekdir; extern __typeof (seekdir) __seekdir;
extern __typeof (dirfd) __dirfd; extern __typeof (dirfd) __dirfd;

43
sysdeps/unix/sysv/linux/opendir.c
View File

@ -23,12 +23,6 @@
#include <not-cancel.h> #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 { enum {
opendir_oflags = O_RDONLY|O_NDELAY|O_DIRECTORY|O_LARGEFILE|O_CLOEXEC opendir_oflags = O_RDONLY|O_NDELAY|O_DIRECTORY|O_LARGEFILE|O_CLOEXEC
}; };
@ -100,39 +94,30 @@ __alloc_dir (int fd, bool close_fd, int flags, const struct stat64 *statp)
file descriptor. */ file descriptor. */
if (!close_fd if (!close_fd
&& __glibc_unlikely (__fcntl64_nocancel (fd, F_SETFD, FD_CLOEXEC) < 0)) && __glibc_unlikely (__fcntl64_nocancel (fd, F_SETFD, FD_CLOEXEC) < 0))
goto lose; 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)");
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
/* Increase allocation if requested, but not if the value appears to /* Increase allocation if requested, but not if the value appears to
be bogus. */ be bogus. It will be between 32Kb and 1Mb. */
if (statp != NULL) size_t allocation = MIN (MAX ((size_t) statp->st_blksize, allocation_size),
allocation = MIN (MAX ((size_t) statp->st_blksize, default_allocation), max_buffer_size);
MAX_DIR_BUFFER_SIZE);
#endif
DIR *dirp = (DIR *) malloc (sizeof (DIR) + allocation); DIR *dirp = (DIR *) malloc (sizeof (DIR) + allocation);
if (dirp == NULL) if (dirp == NULL)
{
allocation = small_allocation;
dirp = (DIR *) malloc (sizeof (DIR) + allocation);
if (dirp == NULL)
lose:
{ {
if (close_fd) if (close_fd)
{
int save_errno = errno;
__close_nocancel_nostatus (fd); __close_nocancel_nostatus (fd);
__set_errno (save_errno);
}
return NULL; return NULL;
} }
}
dirp->fd = fd; dirp->fd = fd;
#if IS_IN (libc) #if IS_IN (libc)