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Message-Id: <1358813390-26466-2-git-send-email-tytso@mit.edu>
Date: Mon, 21 Jan 2013 19:09:49 -0500
From: Theodore Ts'o <tytso@....edu>
To: Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc: Theodore Ts'o <tytso@....edu>
Subject: [PATCH 2/3] contrib: add thread locking and readdir64_r support to spd_readdir
This is part of a series of improvements from a 2008 version of
spd_readdir.c that somehow didn't make it into the version which we
checked into e2fsprogs git tree.
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
---
contrib/spd_readdir.c | 75 ++++++++++++++++++++++++++++++++++++++-------------
1 file changed, 57 insertions(+), 18 deletions(-)
diff --git a/contrib/spd_readdir.c b/contrib/spd_readdir.c
index 30c01b3..910b104 100644
--- a/contrib/spd_readdir.c
+++ b/contrib/spd_readdir.c
@@ -1,21 +1,22 @@
/*
* readdir accelerator
*
- * (C) Copyright 2003, 2004 by Theodore Ts'o.
+ * (C) Copyright 2003, 2004, 2008 by Theodore Ts'o.
+ *
+ * 2008-06-08 Modified by Ross Boylan <RossBoylan stanfordalumni org>
+ * Added support for readdir_r and readdir64_r calls. Note
+ * this has not been tested on anything other than GNU/Linux i386,
+ * and that the regular readdir wrapper will take slightly more
+ * space than Ted's original since it now includes a lock.
*
* Compile using the command:
*
- * gcc -o spd_readdir.so -fPIC -shared spd_readdir.c -ldl
+ * gcc -o spd_readdir.so -shared -fpic spd_readdir.c -ldl
*
* Use it by setting the LD_PRELOAD environment variable:
*
* export LD_PRELOAD=/usr/local/sbin/spd_readdir.so
*
- * Note that this preload is not going to work for all programs. In
- * particular, although it does supply readdir_r(), it is *not* thread
- * safe. So I can't recommend this as something to be dropped in
- * /etc/ld.so.preload.
- *
* %Begin-Header%
* This file may be redistributed under the terms of the GNU Public
* License.
@@ -55,6 +56,7 @@
#else
#define PR_GET_DUMPABLE 3
#endif
+#include <pthread.h>
struct dirent_s {
unsigned long long d_ino;
@@ -66,6 +68,7 @@ struct dirent_s {
struct dir_s {
DIR *dir;
+ pthread_mutex_t lock; /* Mutex lock for this structure. */
int num;
int max;
struct dirent_s *dp;
@@ -83,6 +86,8 @@ static struct dirent *(*real_readdir)(DIR *dir) = 0;
static int (*real_readdir_r)(DIR *dir, struct dirent *entry,
struct dirent **result) = 0;
static struct dirent64 *(*real_readdir64)(DIR *dir) = 0;
+static int (*real_readdir64_r)(DIR *dir, struct dirent64 *entry,
+ struct dirent64 **result) = 0;
static off_t (*real_telldir)(DIR *dir) = 0;
static void (*real_seekdir)(DIR *dir, off_t offset) = 0;
static int (*real_dirfd)(DIR *dir) = 0;
@@ -124,6 +129,7 @@ static void setup_ptr()
real_readdir = dlsym(RTLD_NEXT, "readdir");
real_readdir_r = dlsym(RTLD_NEXT, "readdir_r");
real_readdir64 = dlsym(RTLD_NEXT, "readdir64");
+ real_readdir64_r = dlsym(RTLD_NEXT, "readdir64_r");
real_telldir = dlsym(RTLD_NEXT, "telldir");
real_seekdir = dlsym(RTLD_NEXT, "seekdir");
real_dirfd = dlsym(RTLD_NEXT, "dirfd");
@@ -142,6 +148,8 @@ static void free_cached_dir(struct dir_s *dirstruct)
{
int i;
+ pthread_mutex_destroy(&(dirstruct->lock));
+
if (!dirstruct->dp)
return;
@@ -181,11 +189,14 @@ static int ino_cmp(const void *a, const void *b)
struct dir_s *alloc_dirstruct(DIR *dir)
{
struct dir_s *dirstruct;
+ static pthread_mutexattr_t mutexattr;
+ mutexattr.__align = PTHREAD_MUTEX_RECURSIVE;
dirstruct = malloc(sizeof(struct dir_s));
if (dirstruct)
memset(dirstruct, 0, sizeof(struct dir_s));
dirstruct->dir = dir;
+ pthread_mutex_init(&(dirstruct->lock), &mutexattr);
return dirstruct;
}
@@ -268,7 +279,7 @@ DIR *fdopendir(int fd)
if (!real_fdopendir)
setup_ptr();
- DEBUG_DIR(printf("fdpendir(%d) (%d open)\n", fd, num_open++));
+ DEBUG_DIR(printf("fdopendir(%d) (%d open)\n", fd, num_open++));
dir = (*real_fdopendir)(fd);
if (!dir)
return NULL;
@@ -336,19 +347,19 @@ int readdir_r(DIR *dir, struct dirent *entry, struct dirent **result)
if (dirstruct->direct)
return (*real_readdir_r)(dirstruct->dir, entry, result);
+ pthread_mutex_lock(&(dirstruct->lock));
if (dirstruct->pos >= dirstruct->num) {
*result = NULL;
- return 0;
+ } else {
+ ds = &dirstruct->dp[dirstruct->pos++];
+ entry->d_ino = ds->d_ino;
+ entry->d_off = ds->d_off;
+ entry->d_reclen = ds->d_reclen;
+ entry->d_type = ds->d_type;
+ strncpy(entry->d_name, ds->d_name, sizeof(entry->d_name));
+ *result = entry;
}
-
- ds = &dirstruct->dp[dirstruct->pos++];
- entry->d_ino = ds->d_ino;
- entry->d_off = ds->d_off;
- entry->d_reclen = ds->d_reclen;
- entry->d_type = ds->d_type;
- strncpy(entry->d_name, ds->d_name, sizeof(entry->d_name));
- *result = entry;
-
+ pthread_mutex_unlock(&(dirstruct->lock));
return 0;
}
@@ -374,6 +385,32 @@ struct dirent64 *readdir64(DIR *dir)
return (&dirstruct->ret_dir64);
}
+int readdir64_r (DIR *__restrict dir,
+ struct dirent64 *__restrict entry,
+ struct dirent64 **__restrict result)
+{
+ struct dir_s *dirstruct = (struct dir_s *) dir;
+ struct dirent_s *ds;
+
+ if (dirstruct->direct)
+ return (*real_readdir64_r)(dir, entry, result);
+ pthread_mutex_lock(&(dirstruct->lock));
+ if (dirstruct->pos >= dirstruct->num) {
+ *result = NULL;
+ } else {
+ ds = &dirstruct->dp[dirstruct->pos++];
+ entry->d_ino = ds->d_ino;
+ entry->d_off = ds->d_off;
+ entry->d_reclen = ds->d_reclen;
+ entry->d_type = ds->d_type;
+ strncpy(entry->d_name, ds->d_name,
+ sizeof(entry->d_name));
+ *result = entry;
+ }
+ pthread_mutex_unlock(&(dirstruct->lock));
+ return 0;
+}
+
off_t telldir(DIR *dir)
{
struct dir_s *dirstruct = (struct dir_s *) dir;
@@ -404,9 +441,11 @@ void rewinddir(DIR *dir)
if (dirstruct->direct)
return;
+ pthread_mutex_lock(&(dirstruct->lock));
dirstruct->pos = 0;
free_cached_dir(dirstruct);
cache_dirstruct(dirstruct);
+ pthread_mutex_unlock(&(dirstruct->lock));
}
int dirfd(DIR *dir)
--
1.7.12.rc0.22.gcdd159b
--
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