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Fix some edge cases with rewinddir():

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- In the unionfs case, opendir() and fdopendir() read the directory's full
  contents and cache it.  This cache is not refreshed when rewinddir() is
  called, so rewinddir() will not notice updates to a directory.  Fix this
  by splitting the code to fetch a directory's contents out of
  __opendir_common() into a new _filldir() function and call this from
  rewinddir() when operating on a unionfs directory.
- If rewinddir() is called on a directory opened with fdopendir() before
  any directory entries are fetched, rewinddir() will not adjust the seek
  location of the backing file descriptor.  If the file descriptor passed
  to fdopendir() had a non-zero offset, the rewinddir() will not rewind to
  the beginning.  Fix this by always seeking back to 0 in rewinddir().
  This means the dd_rewind hack can also be removed.

While here, add missing locking to rewinddir().

CR:   	    	https://phabric.freebsd.org/D312
Reviewed by:	jilles
MFC after:	1 week
This commit is contained in:
jhb 2014-07-11 16:16:26 +00:00
parent 75acbf068a
commit 4e6ab5e17b
6 changed files with 226 additions and 165 deletions
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1
include/dirent.h
View File

@ -63,6 +63,7 @@ typedef struct _dirdesc DIR;
#define DTF_NODUP 0x0002 /* don't return duplicate names */
#define DTF_REWIND 0x0004 /* rewind after reading union stack */
#define __DTF_READALL 0x0008 /* everything has been read */
#define __DTF_SKIPREAD 0x0010 /* assume internal buffer is populated */
#else /* !__BSD_VISIBLE */

1
lib/libc/gen/gen-private.h
View File

@ -48,7 +48,6 @@ struct _dirdesc {
char *dd_buf; /* data buffer */
int dd_len; /* size of data buffer */
long dd_seek; /* magic cookie returned by getdirentries */
long dd_rewind; /* magic cookie for rewinding */
int dd_flags; /* flags for readdir */
struct pthread_mutex *dd_lock; /* lock */
struct _telldir *dd_td; /* telldir position recording */

365
lib/libc/gen/opendir.c
View File

@ -49,7 +49,7 @@ __FBSDID("$FreeBSD$");
#include "gen-private.h"
#include "telldir.h"
static DIR * __opendir_common(int, int);
static DIR * __opendir_common(int, int, bool);
/*
* Open a directory.
@ -67,18 +67,10 @@ opendir(const char *name)
DIR *
fdopendir(int fd)
{
struct stat statb;
/* Check that fd is associated with a directory. */
if (_fstat(fd, &statb) != 0)
return (NULL);
if (!S_ISDIR(statb.st_mode)) {
errno = ENOTDIR;
return (NULL);
}
if (_fcntl(fd, F_SETFD, FD_CLOEXEC) == -1)
return (NULL);
return (__opendir_common(fd, DTF_HIDEW|DTF_NODUP));
return (__opendir_common(fd, DTF_HIDEW|DTF_NODUP, true));
}
DIR *
@ -88,11 +80,13 @@ __opendir2(const char *name, int flags)
DIR *dir;
int saved_errno;
if ((flags & (__DTF_READALL | __DTF_SKIPREAD)) != 0)
return (NULL);
if ((fd = _open(name,
O_RDONLY | O_NONBLOCK | O_DIRECTORY | O_CLOEXEC)) == -1)
return (NULL);
dir = __opendir_common(fd, flags);
dir = __opendir_common(fd, flags, false);
if (dir == NULL) {
saved_errno = errno;
_close(fd);
@ -109,23 +103,196 @@ opendir_compar(const void *p1, const void *p2)
(*(const struct dirent **)p2)->d_name));
}
/*
* For a directory at the top of a unionfs stack, the entire directory's
* contents are read and cached locally until the next call to rewinddir().
* For the fdopendir() case, the initial seek position must be preserved.
* For rewinddir(), the full directory should always be re-read from the
* beginning.
*
* If an error occurs, the existing buffer and state of 'dirp' is left
* unchanged.
*/
bool
_filldir(DIR *dirp, bool use_current_pos)
{
struct dirent **dpv;
char *buf, *ddptr, *ddeptr;
off_t pos;
int fd2, incr, len, n, saved_errno, space;
len = 0;
space = 0;
buf = NULL;
ddptr = NULL;
/*
* Use the system page size if that is a multiple of DIRBLKSIZ.
* Hopefully this can be a big win someday by allowing page
* trades to user space to be done by _getdirentries().
*/
incr = getpagesize();
if ((incr % DIRBLKSIZ) != 0)
incr = DIRBLKSIZ;
/*
* The strategy here is to read all the directory
* entries into a buffer, sort the buffer, and
* remove duplicate entries by setting the inode
* number to zero.
*
* We reopen the directory because _getdirentries()
* on a MNT_UNION mount modifies the open directory,
* making it refer to the lower directory after the
* upper directory's entries are exhausted.
* This would otherwise break software that uses
* the directory descriptor for fchdir or *at
* functions, such as fts.c.
*/
if ((fd2 = _openat(dirp->dd_fd, ".", O_RDONLY | O_CLOEXEC)) == -1)
return (false);
if (use_current_pos) {
pos = lseek(dirp->dd_fd, 0, SEEK_CUR);
if (pos == -1 || lseek(fd2, pos, SEEK_SET) == -1) {
saved_errno = errno;
_close(fd2);
errno = saved_errno;
return (false);
}
}
do {
/*
* Always make at least DIRBLKSIZ bytes
* available to _getdirentries
*/
if (space < DIRBLKSIZ) {
space += incr;
len += incr;
buf = reallocf(buf, len);
if (buf == NULL) {
saved_errno = errno;
_close(fd2);
errno = saved_errno;
return (false);
}
ddptr = buf + (len - space);
}
n = _getdirentries(fd2, ddptr, space, &dirp->dd_seek);
if (n > 0) {
ddptr += n;
space -= n;
}
if (n < 0) {
saved_errno = errno;
_close(fd2);
errno = saved_errno;
return (false);
}
} while (n > 0);
_close(fd2);
ddeptr = ddptr;
/*
* There is now a buffer full of (possibly) duplicate
* names.
*/
dirp->dd_buf = buf;
/*
* Go round this loop twice...
*
* Scan through the buffer, counting entries.
* On the second pass, save pointers to each one.
* Then sort the pointers and remove duplicate names.
*/
for (dpv = 0;;) {
n = 0;
ddptr = buf;
while (ddptr < ddeptr) {
struct dirent *dp;
dp = (struct dirent *) ddptr;
if ((long)dp & 03L)
break;
if ((dp->d_reclen <= 0) ||
(dp->d_reclen > (ddeptr + 1 - ddptr)))
break;
ddptr += dp->d_reclen;
if (dp->d_fileno) {
if (dpv)
dpv[n] = dp;
n++;
}
}
if (dpv) {
struct dirent *xp;
/*
* This sort must be stable.
*/
mergesort(dpv, n, sizeof(*dpv), opendir_compar);
dpv[n] = NULL;
xp = NULL;
/*
* Scan through the buffer in sort order,
* zapping the inode number of any
* duplicate names.
*/
for (n = 0; dpv[n]; n++) {
struct dirent *dp = dpv[n];
if ((xp == NULL) ||
strcmp(dp->d_name, xp->d_name)) {
xp = dp;
} else {
dp->d_fileno = 0;
}
if (dp->d_type == DT_WHT &&
(dirp->dd_flags & DTF_HIDEW))
dp->d_fileno = 0;
}
free(dpv);
break;
} else {
dpv = malloc((n+1) * sizeof(struct dirent *));
if (dpv == NULL)
break;
}
}
dirp->dd_len = len;
dirp->dd_size = ddptr - dirp->dd_buf;
return (true);
}
/*
* Common routine for opendir(3), __opendir2(3) and fdopendir(3).
*/
static DIR *
__opendir_common(int fd, int flags)
__opendir_common(int fd, int flags, bool use_current_pos)
{
DIR *dirp;
int incr;
int saved_errno;
int unionstack;
int fd2;
fd2 = -1;
if ((dirp = malloc(sizeof(DIR) + sizeof(struct _telldir))) == NULL)
return (NULL);
dirp->dd_buf = NULL;
dirp->dd_fd = fd;
dirp->dd_flags = flags;
dirp->dd_loc = 0;
dirp->dd_lock = NULL;
dirp->dd_td = (struct _telldir *)((char *)dirp + sizeof(DIR));
LIST_INIT(&dirp->dd_td->td_locq);
dirp->dd_td->td_loccnt = 0;
@ -154,163 +321,39 @@ __opendir_common(int fd, int flags)
}
if (unionstack) {
int len = 0;
int space = 0;
char *buf = 0;
char *ddptr = 0;
char *ddeptr;
int n;
struct dirent **dpv;
/*
* The strategy here is to read all the directory
* entries into a buffer, sort the buffer, and
* remove duplicate entries by setting the inode
* number to zero.
*
* We reopen the directory because _getdirentries()
* on a MNT_UNION mount modifies the open directory,
* making it refer to the lower directory after the
* upper directory's entries are exhausted.
* This would otherwise break software that uses
* the directory descriptor for fchdir or *at
* functions, such as fts.c.
*/
if ((fd2 = _openat(fd, ".", O_RDONLY | O_CLOEXEC)) == -1) {
saved_errno = errno;
free(buf);
free(dirp);
errno = saved_errno;
return (NULL);
}
do {
/*
* Always make at least DIRBLKSIZ bytes
* available to _getdirentries
*/
if (space < DIRBLKSIZ) {
space += incr;
len += incr;
buf = reallocf(buf, len);
if (buf == NULL)
goto fail;
ddptr = buf + (len - space);
}
n = _getdirentries(fd2, ddptr, space, &dirp->dd_seek);
if (n > 0) {
ddptr += n;
space -= n;
}
} while (n > 0);
ddeptr = ddptr;
flags |= __DTF_READALL;
_close(fd2);
fd2 = -1;
/*
* There is now a buffer full of (possibly) duplicate
* names.
*/
dirp->dd_buf = buf;
/*
* Go round this loop twice...
*
* Scan through the buffer, counting entries.
* On the second pass, save pointers to each one.
* Then sort the pointers and remove duplicate names.
*/
for (dpv = 0;;) {
n = 0;
ddptr = buf;
while (ddptr < ddeptr) {
struct dirent *dp;
dp = (struct dirent *) ddptr;
if ((long)dp & 03L)
break;
if ((dp->d_reclen <= 0) ||
(dp->d_reclen > (ddeptr + 1 - ddptr)))
break;
ddptr += dp->d_reclen;
if (dp->d_fileno) {
if (dpv)
dpv[n] = dp;
n++;
}
}
if (dpv) {
struct dirent *xp;
/*
* This sort must be stable.
*/
mergesort(dpv, n, sizeof(*dpv),
opendir_compar);
dpv[n] = NULL;
xp = NULL;
/*
* Scan through the buffer in sort order,
* zapping the inode number of any
* duplicate names.
*/
for (n = 0; dpv[n]; n++) {
struct dirent *dp = dpv[n];
if ((xp == NULL) ||
strcmp(dp->d_name, xp->d_name)) {
xp = dp;
} else {
dp->d_fileno = 0;
}
if (dp->d_type == DT_WHT &&
(flags & DTF_HIDEW))
dp->d_fileno = 0;
}
free(dpv);
break;
} else {
dpv = malloc((n+1) * sizeof(struct dirent *));
if (dpv == NULL)
break;
}
}
dirp->dd_len = len;
dirp->dd_size = ddptr - dirp->dd_buf;
if (!_filldir(dirp, use_current_pos))
goto fail;
dirp->dd_flags |= __DTF_READALL;
} else {
dirp->dd_len = incr;
dirp->dd_size = 0;
dirp->dd_buf = malloc(dirp->dd_len);
if (dirp->dd_buf == NULL)
goto fail;
dirp->dd_seek = 0;
if (use_current_pos) {
/*
* Read the first batch of directory entries
* to prime dd_seek. This also checks if the
* fd passed to fdopendir() is a directory.
*/
dirp->dd_size = _getdirentries(dirp->dd_fd,
dirp->dd_buf, dirp->dd_len, &dirp->dd_seek);
if (dirp->dd_size < 0) {
if (errno == EINVAL)
errno = ENOTDIR;
goto fail;
}
dirp->dd_flags |= __DTF_SKIPREAD;
} else {
dirp->dd_size = 0;
dirp->dd_seek = 0;
}
}
dirp->dd_loc = 0;
dirp->dd_fd = fd;
dirp->dd_flags = flags;
dirp->dd_lock = NULL;
/*
* Set up seek point for rewinddir.
*/
dirp->dd_rewind = telldir(dirp);
return (dirp);
fail:
saved_errno = errno;
if (fd2 != -1)
_close(fd2);
free(dirp->dd_buf);
free(dirp);
errno = saved_errno;
return (NULL);

4
lib/libc/gen/readdir.c
View File

@ -61,12 +61,14 @@ _readdir_unlocked(dirp, skip)
return (NULL);
dirp->dd_loc = 0;
}
if (dirp->dd_loc == 0 && !(dirp->dd_flags & __DTF_READALL)) {
if (dirp->dd_loc == 0 &&
!(dirp->dd_flags & (__DTF_READALL | __DTF_SKIPREAD))) {
dirp->dd_size = _getdirentries(dirp->dd_fd,
dirp->dd_buf, dirp->dd_len, &dirp->dd_seek);
if (dirp->dd_size <= 0)
return (NULL);
}
dirp->dd_flags &= ~__DTF_SKIPREAD;
dp = (struct dirent *)(dirp->dd_buf + dirp->dd_loc);
if ((long)dp & 03L) /* bogus pointer check */
return (NULL);

18
lib/libc/gen/rewinddir.c
View File

@ -33,9 +33,14 @@ static char sccsid[] = "@(#)rewinddir.c 8.1 (Berkeley) 6/8/93";
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "namespace.h"
#include <sys/types.h>
#include <dirent.h>
#include <pthread.h>
#include <unistd.h>
#include "un-namespace.h"
#include "libc_private.h"
#include "gen-private.h"
#include "telldir.h"
@ -44,6 +49,15 @@ rewinddir(dirp)
DIR *dirp;
{
_seekdir(dirp, dirp->dd_rewind);
dirp->dd_rewind = telldir(dirp);
if (__isthreaded)
_pthread_mutex_lock(&dirp->dd_lock);
if (dirp->dd_flags & __DTF_READALL)
_filldir(dirp, false);
else if (dirp->dd_seek != 0) {
(void) lseek(dirp->dd_fd, 0, SEEK_SET);
dirp->dd_seek = 0;
}
dirp->dd_loc = 0;
if (__isthreaded)
_pthread_mutex_unlock(&dirp->dd_lock);
}

2
lib/libc/gen/telldir.h
View File

@ -36,6 +36,7 @@
#define _TELLDIR_H_
#include <sys/queue.h>
#include <stdbool.h>
/*
* One of these structures is malloced to describe the current directory
@ -59,6 +60,7 @@ struct _telldir {
long td_loccnt; /* index of entry for sequential readdir's */
};
bool _filldir(DIR *, bool);
struct dirent *_readdir_unlocked(DIR *, int);
void _reclaim_telldir(DIR *);
void _seekdir(DIR *, long);