* [Qemu-devel] [PATCH 1/4] 9p: drop useless out: label
2016-06-02 8:51 [Qemu-devel] [PATCH 0/4] 9p: get rid of readdir_r() Greg Kurz
@ 2016-06-02 8:52 ` Greg Kurz
2016-06-02 19:57 ` Eric Blake
2016-06-02 8:52 ` [Qemu-devel] [PATCH 2/4] 9p: introduce the V9fsDir type Greg Kurz
` (3 subsequent siblings)
4 siblings, 1 reply; 15+ messages in thread
From: Greg Kurz @ 2016-06-02 8:52 UTC (permalink / raw)
To: Greg Kurz; +Cc: Aneesh Kumar K.V, qemu-devel
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
---
hw/9pfs/9p.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index 587e901f81cc..12bd688f37d3 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -1646,15 +1646,15 @@ static int v9fs_do_readdir_with_stat(V9fsPDU *pdu,
}
err = v9fs_co_name_to_path(pdu, &fidp->path, dent->d_name, &path);
if (err < 0) {
- goto out;
+ break;
}
err = v9fs_co_lstat(pdu, &path, &stbuf);
if (err < 0) {
- goto out;
+ break;
}
err = stat_to_v9stat(pdu, &path, &stbuf, &v9stat);
if (err < 0) {
- goto out;
+ break;
}
/* 11 = 7 + 4 (7 = start offset, 4 = space for storing count) */
len = pdu_marshal(pdu, 11 + count, "S", &v9stat);
@@ -1671,7 +1671,7 @@ static int v9fs_do_readdir_with_stat(V9fsPDU *pdu,
v9fs_path_free(&path);
saved_dir_pos = dent->d_off;
}
-out:
+
g_free(dent);
v9fs_path_free(&path);
if (err < 0) {
^ permalink raw reply related [flat|nested] 15+ messages in thread* [Qemu-devel] [PATCH 2/4] 9p: introduce the V9fsDir type
2016-06-02 8:51 [Qemu-devel] [PATCH 0/4] 9p: get rid of readdir_r() Greg Kurz
2016-06-02 8:52 ` [Qemu-devel] [PATCH 1/4] 9p: drop useless out: label Greg Kurz
@ 2016-06-02 8:52 ` Greg Kurz
2016-06-02 20:05 ` Eric Blake
2016-06-02 8:52 ` [Qemu-devel] [PATCH 3/4] 9p: add locking to V9fsDir Greg Kurz
` (2 subsequent siblings)
4 siblings, 1 reply; 15+ messages in thread
From: Greg Kurz @ 2016-06-02 8:52 UTC (permalink / raw)
To: Greg Kurz; +Cc: Aneesh Kumar K.V, qemu-devel
If we are to switch back to readdir(), we need a more complex type than
DIR * to be able to serialize concurrent accesses to the directory stream.
This patch introduces a placeholder type and fixes all users.
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
---
hw/9pfs/9p-handle.c | 18 +++++++++---------
hw/9pfs/9p-local.c | 18 +++++++++---------
hw/9pfs/9p-proxy.c | 20 ++++++++++----------
hw/9pfs/9p.c | 12 ++++++------
hw/9pfs/9p.h | 6 +++++-
5 files changed, 39 insertions(+), 35 deletions(-)
diff --git a/hw/9pfs/9p-handle.c b/hw/9pfs/9p-handle.c
index 894041488abb..c5df05300700 100644
--- a/hw/9pfs/9p-handle.c
+++ b/hw/9pfs/9p-handle.c
@@ -112,7 +112,7 @@ static int handle_close(FsContext *ctx, V9fsFidOpenState *fs)
static int handle_closedir(FsContext *ctx, V9fsFidOpenState *fs)
{
- return closedir(fs->dir);
+ return closedir(fs->dir.stream);
}
static int handle_open(FsContext *ctx, V9fsPath *fs_path,
@@ -132,8 +132,8 @@ static int handle_opendir(FsContext *ctx,
if (ret < 0) {
return -1;
}
- fs->dir = fdopendir(ret);
- if (!fs->dir) {
+ fs->dir.stream = fdopendir(ret);
+ if (!fs->dir.stream) {
return -1;
}
return 0;
@@ -141,24 +141,24 @@ static int handle_opendir(FsContext *ctx,
static void handle_rewinddir(FsContext *ctx, V9fsFidOpenState *fs)
{
- rewinddir(fs->dir);
+ rewinddir(fs->dir.stream);
}
static off_t handle_telldir(FsContext *ctx, V9fsFidOpenState *fs)
{
- return telldir(fs->dir);
+ return telldir(fs->dir.stream);
}
static int handle_readdir_r(FsContext *ctx, V9fsFidOpenState *fs,
struct dirent *entry,
struct dirent **result)
{
- return readdir_r(fs->dir, entry, result);
+ return readdir_r(fs->dir.stream, entry, result);
}
static void handle_seekdir(FsContext *ctx, V9fsFidOpenState *fs, off_t off)
{
- seekdir(fs->dir, off);
+ seekdir(fs->dir.stream, off);
}
static ssize_t handle_preadv(FsContext *ctx, V9fsFidOpenState *fs,
@@ -262,7 +262,7 @@ static int handle_fstat(FsContext *fs_ctx, int fid_type,
int fd;
if (fid_type == P9_FID_DIR) {
- fd = dirfd(fs->dir);
+ fd = dirfd(fs->dir.stream);
} else {
fd = fs->fd;
}
@@ -409,7 +409,7 @@ static int handle_fsync(FsContext *ctx, int fid_type,
int fd;
if (fid_type == P9_FID_DIR) {
- fd = dirfd(fs->dir);
+ fd = dirfd(fs->dir.stream);
} else {
fd = fs->fd;
}
diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
index 16f45f4854ca..3281acdef164 100644
--- a/hw/9pfs/9p-local.c
+++ b/hw/9pfs/9p-local.c
@@ -348,7 +348,7 @@ static int local_close(FsContext *ctx, V9fsFidOpenState *fs)
static int local_closedir(FsContext *ctx, V9fsFidOpenState *fs)
{
- return closedir(fs->dir);
+ return closedir(fs->dir.stream);
}
static int local_open(FsContext *ctx, V9fsPath *fs_path,
@@ -370,9 +370,9 @@ static int local_opendir(FsContext *ctx,
char *path = fs_path->data;
buffer = rpath(ctx, path);
- fs->dir = opendir(buffer);
+ fs->dir.stream = opendir(buffer);
g_free(buffer);
- if (!fs->dir) {
+ if (!fs->dir.stream) {
return -1;
}
return 0;
@@ -380,12 +380,12 @@ static int local_opendir(FsContext *ctx,
static void local_rewinddir(FsContext *ctx, V9fsFidOpenState *fs)
{
- rewinddir(fs->dir);
+ rewinddir(fs->dir.stream);
}
static off_t local_telldir(FsContext *ctx, V9fsFidOpenState *fs)
{
- return telldir(fs->dir);
+ return telldir(fs->dir.stream);
}
static int local_readdir_r(FsContext *ctx, V9fsFidOpenState *fs,
@@ -395,7 +395,7 @@ static int local_readdir_r(FsContext *ctx, V9fsFidOpenState *fs,
int ret;
again:
- ret = readdir_r(fs->dir, entry, result);
+ ret = readdir_r(fs->dir.stream, entry, result);
if (ctx->export_flags & V9FS_SM_MAPPED) {
entry->d_type = DT_UNKNOWN;
} else if (ctx->export_flags & V9FS_SM_MAPPED_FILE) {
@@ -411,7 +411,7 @@ again:
static void local_seekdir(FsContext *ctx, V9fsFidOpenState *fs, off_t off)
{
- seekdir(fs->dir, off);
+ seekdir(fs->dir.stream, off);
}
static ssize_t local_preadv(FsContext *ctx, V9fsFidOpenState *fs,
@@ -610,7 +610,7 @@ static int local_fstat(FsContext *fs_ctx, int fid_type,
int err, fd;
if (fid_type == P9_FID_DIR) {
- fd = dirfd(fs->dir);
+ fd = dirfd(fs->dir.stream);
} else {
fd = fs->fd;
}
@@ -998,7 +998,7 @@ static int local_fsync(FsContext *ctx, int fid_type,
int fd;
if (fid_type == P9_FID_DIR) {
- fd = dirfd(fs->dir);
+ fd = dirfd(fs->dir.stream);
} else {
fd = fs->fd;
}
diff --git a/hw/9pfs/9p-proxy.c b/hw/9pfs/9p-proxy.c
index 00a4eb2a7bcf..63b074781589 100644
--- a/hw/9pfs/9p-proxy.c
+++ b/hw/9pfs/9p-proxy.c
@@ -633,7 +633,7 @@ static int proxy_close(FsContext *ctx, V9fsFidOpenState *fs)
static int proxy_closedir(FsContext *ctx, V9fsFidOpenState *fs)
{
- return closedir(fs->dir);
+ return closedir(fs->dir.stream);
}
static int proxy_open(FsContext *ctx, V9fsPath *fs_path,
@@ -652,14 +652,14 @@ static int proxy_opendir(FsContext *ctx,
{
int serrno, fd;
- fs->dir = NULL;
+ fs->dir.stream = NULL;
fd = v9fs_request(ctx->private, T_OPEN, NULL, "sd", fs_path, O_DIRECTORY);
if (fd < 0) {
errno = -fd;
return -1;
}
- fs->dir = fdopendir(fd);
- if (!fs->dir) {
+ fs->dir.stream = fdopendir(fd);
+ if (!fs->dir.stream) {
serrno = errno;
close(fd);
errno = serrno;
@@ -670,24 +670,24 @@ static int proxy_opendir(FsContext *ctx,
static void proxy_rewinddir(FsContext *ctx, V9fsFidOpenState *fs)
{
- rewinddir(fs->dir);
+ rewinddir(fs->dir.stream);
}
static off_t proxy_telldir(FsContext *ctx, V9fsFidOpenState *fs)
{
- return telldir(fs->dir);
+ return telldir(fs->dir.stream);
}
static int proxy_readdir_r(FsContext *ctx, V9fsFidOpenState *fs,
struct dirent *entry,
struct dirent **result)
{
- return readdir_r(fs->dir, entry, result);
+ return readdir_r(fs->dir.stream, entry, result);
}
static void proxy_seekdir(FsContext *ctx, V9fsFidOpenState *fs, off_t off)
{
- seekdir(fs->dir, off);
+ seekdir(fs->dir.stream, off);
}
static ssize_t proxy_preadv(FsContext *ctx, V9fsFidOpenState *fs,
@@ -791,7 +791,7 @@ static int proxy_fstat(FsContext *fs_ctx, int fid_type,
int fd;
if (fid_type == P9_FID_DIR) {
- fd = dirfd(fs->dir);
+ fd = dirfd(fs->dir.stream);
} else {
fd = fs->fd;
}
@@ -936,7 +936,7 @@ static int proxy_fsync(FsContext *ctx, int fid_type,
int fd;
if (fid_type == P9_FID_DIR) {
- fd = dirfd(fs->dir);
+ fd = dirfd(fs->dir.stream);
} else {
fd = fs->fd;
}
diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index 12bd688f37d3..451ecbde0b08 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -231,7 +231,7 @@ static int v9fs_reopen_fid(V9fsPDU *pdu, V9fsFidState *f)
} while (err == -EINTR && !pdu->cancelled);
}
} else if (f->fid_type == P9_FID_DIR) {
- if (f->fs.dir == NULL) {
+ if (f->fs.dir.stream == NULL) {
do {
err = v9fs_co_opendir(pdu, f);
} while (err == -EINTR && !pdu->cancelled);
@@ -345,7 +345,7 @@ static int free_fid(V9fsPDU *pdu, V9fsFidState *fidp)
retval = v9fs_co_close(pdu, &fidp->fs);
}
} else if (fidp->fid_type == P9_FID_DIR) {
- if (fidp->fs.dir != NULL) {
+ if (fidp->fs.dir.stream != NULL) {
retval = v9fs_co_closedir(pdu, &fidp->fs);
}
} else if (fidp->fid_type == P9_FID_XATTR) {
@@ -443,7 +443,7 @@ void v9fs_reclaim_fd(V9fsPDU *pdu)
reclaim_count++;
}
} else if (f->fid_type == P9_FID_DIR) {
- if (f->fs.dir != NULL) {
+ if (f->fs.dir.stream != NULL) {
/*
* Up the reference count so that
* a clunk request won't free this fid
@@ -451,8 +451,8 @@ void v9fs_reclaim_fd(V9fsPDU *pdu)
f->ref++;
f->rclm_lst = reclaim_list;
reclaim_list = f;
- f->fs_reclaim.dir = f->fs.dir;
- f->fs.dir = NULL;
+ f->fs_reclaim.dir.stream = f->fs.dir.stream;
+ f->fs.dir.stream = NULL;
reclaim_count++;
}
}
@@ -1887,7 +1887,7 @@ static void v9fs_readdir(void *opaque)
retval = -EINVAL;
goto out_nofid;
}
- if (!fidp->fs.dir) {
+ if (!fidp->fs.dir.stream) {
retval = -EINVAL;
goto out;
}
diff --git a/hw/9pfs/9p.h b/hw/9pfs/9p.h
index 43378943cdda..92ee309ef4ba 100644
--- a/hw/9pfs/9p.h
+++ b/hw/9pfs/9p.h
@@ -167,13 +167,17 @@ typedef struct V9fsXattr
int flags;
} V9fsXattr;
+typedef struct V9fsDir {
+ DIR *stream;
+} V9fsDir;
+
/*
* Filled by fs driver on open and other
* calls.
*/
union V9fsFidOpenState {
int fd;
- DIR *dir;
+ V9fsDir dir;
V9fsXattr xattr;
/*
* private pointer for fs drivers, that
^ permalink raw reply related [flat|nested] 15+ messages in thread* [Qemu-devel] [PATCH 3/4] 9p: add locking to V9fsDir
2016-06-02 8:51 [Qemu-devel] [PATCH 0/4] 9p: get rid of readdir_r() Greg Kurz
2016-06-02 8:52 ` [Qemu-devel] [PATCH 1/4] 9p: drop useless out: label Greg Kurz
2016-06-02 8:52 ` [Qemu-devel] [PATCH 2/4] 9p: introduce the V9fsDir type Greg Kurz
@ 2016-06-02 8:52 ` Greg Kurz
2016-06-02 20:46 ` Eric Blake
2016-06-02 8:52 ` [Qemu-devel] [PATCH 4/4] 9p: switch back to readdir() Greg Kurz
2016-06-02 9:33 ` [Qemu-devel] [PATCH 0/4] 9p: get rid of readdir_r() Peter Maydell
4 siblings, 1 reply; 15+ messages in thread
From: Greg Kurz @ 2016-06-02 8:52 UTC (permalink / raw)
To: Greg Kurz; +Cc: Aneesh Kumar K.V, qemu-devel
If several threads call concurrently readdir() with the same directory
stream pointer, it is possible that they all get a pointer to the same
dirent structure, whose content is overwritten each time readdir() is
called.
We must thus serialize accesses to the dirent structure.
This may be achieved with a mutex like below:
lock_mutex();
readdir();
// work with the dirent
unlock_mutex();
This patch adds all the locking, to prepare the switch to readdir().
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
---
hw/9pfs/9p.c | 21 +++++++++++++++++++++
hw/9pfs/9p.h | 16 ++++++++++++++++
2 files changed, 37 insertions(+)
diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index 451ecbde0b08..3ed077b25b98 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -300,6 +300,9 @@ static V9fsFidState *alloc_fid(V9fsState *s, int32_t fid)
f->next = s->fid_list;
s->fid_list = f;
+ v9fs_readdir_init(&f->fs.dir);
+ v9fs_readdir_init(&f->fs_reclaim.dir);
+
return f;
}
@@ -1640,6 +1643,9 @@ static int v9fs_do_readdir_with_stat(V9fsPDU *pdu,
while (1) {
v9fs_path_init(&path);
+
+ v9fs_readdir_lock(&fidp->fs.dir);
+
err = v9fs_co_readdir_r(pdu, fidp, dent, &result);
if (err || !result) {
break;
@@ -1658,6 +1664,9 @@ static int v9fs_do_readdir_with_stat(V9fsPDU *pdu,
}
/* 11 = 7 + 4 (7 = start offset, 4 = space for storing count) */
len = pdu_marshal(pdu, 11 + count, "S", &v9stat);
+
+ v9fs_readdir_unlock(&fidp->fs.dir);
+
if ((len != (v9stat.size + 2)) || ((count + len) > max_count)) {
/* Ran out of buffer. Set dir back to old position and return */
v9fs_co_seekdir(pdu, fidp, saved_dir_pos);
@@ -1672,6 +1681,8 @@ static int v9fs_do_readdir_with_stat(V9fsPDU *pdu,
saved_dir_pos = dent->d_off;
}
+ v9fs_readdir_unlock(&fidp->fs.dir);
+
g_free(dent);
v9fs_path_free(&path);
if (err < 0) {
@@ -1819,6 +1830,8 @@ static int v9fs_do_readdir(V9fsPDU *pdu,
dent = g_malloc(sizeof(struct dirent));
while (1) {
+ v9fs_readdir_lock(&fidp->fs.dir);
+
err = v9fs_co_readdir_r(pdu, fidp, dent, &result);
if (err || !result) {
break;
@@ -1826,6 +1839,8 @@ static int v9fs_do_readdir(V9fsPDU *pdu,
v9fs_string_init(&name);
v9fs_string_sprintf(&name, "%s", dent->d_name);
if ((count + v9fs_readdir_data_size(&name)) > max_count) {
+ v9fs_readdir_unlock(&fidp->fs.dir);
+
/* Ran out of buffer. Set dir back to old position and return */
v9fs_co_seekdir(pdu, fidp, saved_dir_pos);
v9fs_string_free(&name);
@@ -1847,6 +1862,9 @@ static int v9fs_do_readdir(V9fsPDU *pdu,
len = pdu_marshal(pdu, 11 + count, "Qqbs",
&qid, dent->d_off,
dent->d_type, &name);
+
+ v9fs_readdir_unlock(&fidp->fs.dir);
+
if (len < 0) {
v9fs_co_seekdir(pdu, fidp, saved_dir_pos);
v9fs_string_free(&name);
@@ -1857,6 +1875,9 @@ static int v9fs_do_readdir(V9fsPDU *pdu,
v9fs_string_free(&name);
saved_dir_pos = dent->d_off;
}
+
+ v9fs_readdir_unlock(&fidp->fs.dir);
+
g_free(dent);
if (err < 0) {
return err;
diff --git a/hw/9pfs/9p.h b/hw/9pfs/9p.h
index 92ee309ef4ba..46d787627a4c 100644
--- a/hw/9pfs/9p.h
+++ b/hw/9pfs/9p.h
@@ -169,8 +169,24 @@ typedef struct V9fsXattr
typedef struct V9fsDir {
DIR *stream;
+ QemuMutex readdir_mutex;
} V9fsDir;
+static inline void v9fs_readdir_lock(V9fsDir *dir)
+{
+ qemu_mutex_lock(&dir->readdir_mutex);
+}
+
+static inline void v9fs_readdir_unlock(V9fsDir *dir)
+{
+ qemu_mutex_unlock(&dir->readdir_mutex);
+}
+
+static inline void v9fs_readdir_init(V9fsDir *dir)
+{
+ qemu_mutex_init(&dir->readdir_mutex);
+}
+
/*
* Filled by fs driver on open and other
* calls.
^ permalink raw reply related [flat|nested] 15+ messages in thread* [Qemu-devel] [PATCH 4/4] 9p: switch back to readdir()
2016-06-02 8:51 [Qemu-devel] [PATCH 0/4] 9p: get rid of readdir_r() Greg Kurz
` (2 preceding siblings ...)
2016-06-02 8:52 ` [Qemu-devel] [PATCH 3/4] 9p: add locking to V9fsDir Greg Kurz
@ 2016-06-02 8:52 ` Greg Kurz
2016-06-02 21:00 ` Eric Blake
2016-06-02 9:33 ` [Qemu-devel] [PATCH 0/4] 9p: get rid of readdir_r() Peter Maydell
4 siblings, 1 reply; 15+ messages in thread
From: Greg Kurz @ 2016-06-02 8:52 UTC (permalink / raw)
To: Greg Kurz; +Cc: Aneesh Kumar K.V, qemu-devel
This patch changes the 9p code to use readdir() again instead of
readdir_r(), which is deprecated in glibc 2.24.
All the locking was put in place by a previous patch.
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
---
fsdev/file-op-9p.h | 3 +--
hw/9pfs/9p-handle.c | 8 +++-----
hw/9pfs/9p-local.c | 20 +++++++++++---------
hw/9pfs/9p-proxy.c | 8 +++-----
hw/9pfs/9p-synth.c | 23 ++++++++++-------------
hw/9pfs/9p-synth.h | 1 +
hw/9pfs/9p.c | 21 ++++++---------------
hw/9pfs/codir.c | 12 +++++++-----
hw/9pfs/coth.h | 3 +--
9 files changed, 43 insertions(+), 56 deletions(-)
diff --git a/fsdev/file-op-9p.h b/fsdev/file-op-9p.h
index 1095fcc95757..55614949740d 100644
--- a/fsdev/file-op-9p.h
+++ b/fsdev/file-op-9p.h
@@ -118,8 +118,7 @@ struct FileOperations
int, FsCred *, V9fsFidOpenState *);
void (*rewinddir)(FsContext *, V9fsFidOpenState *);
off_t (*telldir)(FsContext *, V9fsFidOpenState *);
- int (*readdir_r)(FsContext *, V9fsFidOpenState *,
- struct dirent *, struct dirent **);
+ struct dirent * (*readdir)(FsContext *, V9fsFidOpenState *);
void (*seekdir)(FsContext *, V9fsFidOpenState *, off_t);
ssize_t (*preadv)(FsContext *, V9fsFidOpenState *,
const struct iovec *, int, off_t);
diff --git a/hw/9pfs/9p-handle.c b/hw/9pfs/9p-handle.c
index c5df05300700..3d77594f9245 100644
--- a/hw/9pfs/9p-handle.c
+++ b/hw/9pfs/9p-handle.c
@@ -149,11 +149,9 @@ static off_t handle_telldir(FsContext *ctx, V9fsFidOpenState *fs)
return telldir(fs->dir.stream);
}
-static int handle_readdir_r(FsContext *ctx, V9fsFidOpenState *fs,
- struct dirent *entry,
- struct dirent **result)
+static struct dirent *handle_readdir(FsContext *ctx, V9fsFidOpenState *fs)
{
- return readdir_r(fs->dir.stream, entry, result);
+ return readdir(fs->dir.stream);
}
static void handle_seekdir(FsContext *ctx, V9fsFidOpenState *fs, off_t off)
@@ -681,7 +679,7 @@ FileOperations handle_ops = {
.opendir = handle_opendir,
.rewinddir = handle_rewinddir,
.telldir = handle_telldir,
- .readdir_r = handle_readdir_r,
+ .readdir = handle_readdir,
.seekdir = handle_seekdir,
.preadv = handle_preadv,
.pwritev = handle_pwritev,
diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
index 3281acdef164..3f271fcbd2c5 100644
--- a/hw/9pfs/9p-local.c
+++ b/hw/9pfs/9p-local.c
@@ -388,25 +388,27 @@ static off_t local_telldir(FsContext *ctx, V9fsFidOpenState *fs)
return telldir(fs->dir.stream);
}
-static int local_readdir_r(FsContext *ctx, V9fsFidOpenState *fs,
- struct dirent *entry,
- struct dirent **result)
+static struct dirent *local_readdir(FsContext *ctx, V9fsFidOpenState *fs)
{
- int ret;
+ struct dirent *entry;
again:
- ret = readdir_r(fs->dir.stream, entry, result);
+ entry = readdir(fs->dir.stream);
+ if (!entry) {
+ return NULL;
+ }
+
if (ctx->export_flags & V9FS_SM_MAPPED) {
entry->d_type = DT_UNKNOWN;
} else if (ctx->export_flags & V9FS_SM_MAPPED_FILE) {
- if (!ret && *result != NULL &&
- !strcmp(entry->d_name, VIRTFS_META_DIR)) {
+ if (!strcmp(entry->d_name, VIRTFS_META_DIR)) {
/* skp the meta data directory */
goto again;
}
entry->d_type = DT_UNKNOWN;
}
- return ret;
+
+ return entry;
}
static void local_seekdir(FsContext *ctx, V9fsFidOpenState *fs, off_t off)
@@ -1254,7 +1256,7 @@ FileOperations local_ops = {
.opendir = local_opendir,
.rewinddir = local_rewinddir,
.telldir = local_telldir,
- .readdir_r = local_readdir_r,
+ .readdir = local_readdir,
.seekdir = local_seekdir,
.preadv = local_preadv,
.pwritev = local_pwritev,
diff --git a/hw/9pfs/9p-proxy.c b/hw/9pfs/9p-proxy.c
index 63b074781589..f265501eac1d 100644
--- a/hw/9pfs/9p-proxy.c
+++ b/hw/9pfs/9p-proxy.c
@@ -678,11 +678,9 @@ static off_t proxy_telldir(FsContext *ctx, V9fsFidOpenState *fs)
return telldir(fs->dir.stream);
}
-static int proxy_readdir_r(FsContext *ctx, V9fsFidOpenState *fs,
- struct dirent *entry,
- struct dirent **result)
+static struct dirent *proxy_readdir(FsContext *ctx, V9fsFidOpenState *fs)
{
- return readdir_r(fs->dir.stream, entry, result);
+ return readdir(fs->dir.stream);
}
static void proxy_seekdir(FsContext *ctx, V9fsFidOpenState *fs, off_t off)
@@ -1192,7 +1190,7 @@ FileOperations proxy_ops = {
.opendir = proxy_opendir,
.rewinddir = proxy_rewinddir,
.telldir = proxy_telldir,
- .readdir_r = proxy_readdir_r,
+ .readdir = proxy_readdir,
.seekdir = proxy_seekdir,
.preadv = proxy_preadv,
.pwritev = proxy_pwritev,
diff --git a/hw/9pfs/9p-synth.c b/hw/9pfs/9p-synth.c
index 8e504130d94b..73c8be816bbb 100644
--- a/hw/9pfs/9p-synth.c
+++ b/hw/9pfs/9p-synth.c
@@ -223,8 +223,8 @@ static void v9fs_synth_direntry(V9fsSynthNode *node,
entry->d_off = off + 1;
}
-static int v9fs_synth_get_dentry(V9fsSynthNode *dir, struct dirent *entry,
- struct dirent **result, off_t off)
+static struct dirent *v9fs_synth_get_dentry(V9fsSynthNode *dir,
+ struct dirent *entry, off_t off)
{
int i = 0;
V9fsSynthNode *node;
@@ -240,25 +240,22 @@ static int v9fs_synth_get_dentry(V9fsSynthNode *dir, struct dirent *entry,
rcu_read_unlock();
if (!node) {
/* end of directory */
- *result = NULL;
- return 0;
+ return NULL;
}
v9fs_synth_direntry(node, entry, off);
- *result = entry;
- return 0;
+ return entry;
}
-static int v9fs_synth_readdir_r(FsContext *ctx, V9fsFidOpenState *fs,
- struct dirent *entry, struct dirent **result)
+static struct dirent *v9fs_synth_readdir(FsContext *ctx, V9fsFidOpenState *fs)
{
- int ret;
+ struct dirent *entry;
V9fsSynthOpenState *synth_open = fs->private;
V9fsSynthNode *node = synth_open->node;
- ret = v9fs_synth_get_dentry(node, entry, result, synth_open->offset);
- if (!ret && *result != NULL) {
+ entry = v9fs_synth_get_dentry(node, &synth_open->dent, synth_open->offset);
+ if (entry) {
synth_open->offset++;
}
- return ret;
+ return entry;
}
static int v9fs_synth_open(FsContext *ctx, V9fsPath *fs_path,
@@ -544,7 +541,7 @@ FileOperations synth_ops = {
.opendir = v9fs_synth_opendir,
.rewinddir = v9fs_synth_rewinddir,
.telldir = v9fs_synth_telldir,
- .readdir_r = v9fs_synth_readdir_r,
+ .readdir = v9fs_synth_readdir,
.seekdir = v9fs_synth_seekdir,
.preadv = v9fs_synth_preadv,
.pwritev = v9fs_synth_pwritev,
diff --git a/hw/9pfs/9p-synth.h b/hw/9pfs/9p-synth.h
index 82962512a199..7c8441bd6cf9 100644
--- a/hw/9pfs/9p-synth.h
+++ b/hw/9pfs/9p-synth.h
@@ -40,6 +40,7 @@ struct V9fsSynthNode {
typedef struct V9fsSynthOpenState {
off_t offset;
V9fsSynthNode *node;
+ struct dirent dent;
} V9fsSynthOpenState;
extern int qemu_v9fs_synth_mkdir(V9fsSynthNode *parent, int mode,
diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index 3ed077b25b98..ef7ef3f64ca7 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -1631,7 +1631,7 @@ static int v9fs_do_readdir_with_stat(V9fsPDU *pdu,
int32_t count = 0;
struct stat stbuf;
off_t saved_dir_pos;
- struct dirent *dent, *result;
+ struct dirent *dent;
/* save the directory position */
saved_dir_pos = v9fs_co_telldir(pdu, fidp);
@@ -1639,15 +1639,13 @@ static int v9fs_do_readdir_with_stat(V9fsPDU *pdu,
return saved_dir_pos;
}
- dent = g_malloc(sizeof(struct dirent));
-
while (1) {
v9fs_path_init(&path);
v9fs_readdir_lock(&fidp->fs.dir);
- err = v9fs_co_readdir_r(pdu, fidp, dent, &result);
- if (err || !result) {
+ err = v9fs_co_readdir(pdu, fidp, &dent);
+ if (err || !dent) {
break;
}
err = v9fs_co_name_to_path(pdu, &fidp->path, dent->d_name, &path);
@@ -1672,7 +1670,6 @@ static int v9fs_do_readdir_with_stat(V9fsPDU *pdu,
v9fs_co_seekdir(pdu, fidp, saved_dir_pos);
v9fs_stat_free(&v9stat);
v9fs_path_free(&path);
- g_free(dent);
return count;
}
count += len;
@@ -1683,7 +1680,6 @@ static int v9fs_do_readdir_with_stat(V9fsPDU *pdu,
v9fs_readdir_unlock(&fidp->fs.dir);
- g_free(dent);
v9fs_path_free(&path);
if (err < 0) {
return err;
@@ -1819,7 +1815,7 @@ static int v9fs_do_readdir(V9fsPDU *pdu,
int len, err = 0;
int32_t count = 0;
off_t saved_dir_pos;
- struct dirent *dent, *result;
+ struct dirent *dent;
/* save the directory position */
saved_dir_pos = v9fs_co_telldir(pdu, fidp);
@@ -1827,13 +1823,11 @@ static int v9fs_do_readdir(V9fsPDU *pdu,
return saved_dir_pos;
}
- dent = g_malloc(sizeof(struct dirent));
-
while (1) {
v9fs_readdir_lock(&fidp->fs.dir);
- err = v9fs_co_readdir_r(pdu, fidp, dent, &result);
- if (err || !result) {
+ err = v9fs_co_readdir(pdu, fidp, &dent);
+ if (err || !dent) {
break;
}
v9fs_string_init(&name);
@@ -1844,7 +1838,6 @@ static int v9fs_do_readdir(V9fsPDU *pdu,
/* Ran out of buffer. Set dir back to old position and return */
v9fs_co_seekdir(pdu, fidp, saved_dir_pos);
v9fs_string_free(&name);
- g_free(dent);
return count;
}
/*
@@ -1868,7 +1861,6 @@ static int v9fs_do_readdir(V9fsPDU *pdu,
if (len < 0) {
v9fs_co_seekdir(pdu, fidp, saved_dir_pos);
v9fs_string_free(&name);
- g_free(dent);
return len;
}
count += len;
@@ -1878,7 +1870,6 @@ static int v9fs_do_readdir(V9fsPDU *pdu,
v9fs_readdir_unlock(&fidp->fs.dir);
- g_free(dent);
if (err < 0) {
return err;
}
diff --git a/hw/9pfs/codir.c b/hw/9pfs/codir.c
index 8e3ba17baeed..80373dce5261 100644
--- a/hw/9pfs/codir.c
+++ b/hw/9pfs/codir.c
@@ -17,8 +17,7 @@
#include "qemu/coroutine.h"
#include "coth.h"
-int v9fs_co_readdir_r(V9fsPDU *pdu, V9fsFidState *fidp, struct dirent *dent,
- struct dirent **result)
+int v9fs_co_readdir(V9fsPDU *pdu, V9fsFidState *fidp, struct dirent **dent)
{
int err;
V9fsState *s = pdu->s;
@@ -28,11 +27,14 @@ int v9fs_co_readdir_r(V9fsPDU *pdu, V9fsFidState *fidp, struct dirent *dent,
}
v9fs_co_run_in_worker(
{
- errno = 0;
- err = s->ops->readdir_r(&s->ctx, &fidp->fs, dent, result);
- if (!*result && errno) {
+ struct dirent *entry;
+ int old_errno = errno;
+
+ entry = s->ops->readdir(&s->ctx, &fidp->fs);
+ if (!entry && errno != old_errno) {
err = -errno;
} else {
+ *dent = entry;
err = 0;
}
});
diff --git a/hw/9pfs/coth.h b/hw/9pfs/coth.h
index 6adc773d4664..5b02a63ad9fd 100644
--- a/hw/9pfs/coth.h
+++ b/hw/9pfs/coth.h
@@ -49,8 +49,7 @@
extern void co_run_in_worker_bh(void *);
extern int v9fs_co_readlink(V9fsPDU *, V9fsPath *, V9fsString *);
-extern int v9fs_co_readdir_r(V9fsPDU *, V9fsFidState *,
- struct dirent *, struct dirent **result);
+extern int v9fs_co_readdir(V9fsPDU *, V9fsFidState *, struct dirent **);
extern off_t v9fs_co_telldir(V9fsPDU *, V9fsFidState *);
extern void v9fs_co_seekdir(V9fsPDU *, V9fsFidState *, off_t);
extern void v9fs_co_rewinddir(V9fsPDU *, V9fsFidState *);
^ permalink raw reply related [flat|nested] 15+ messages in thread* Re: [Qemu-devel] [PATCH 4/4] 9p: switch back to readdir()
2016-06-02 8:52 ` [Qemu-devel] [PATCH 4/4] 9p: switch back to readdir() Greg Kurz
@ 2016-06-02 21:00 ` Eric Blake
2016-06-03 6:29 ` Greg Kurz
0 siblings, 1 reply; 15+ messages in thread
From: Eric Blake @ 2016-06-02 21:00 UTC (permalink / raw)
To: Greg Kurz; +Cc: Aneesh Kumar K.V, qemu-devel
[-- Attachment #1: Type: text/plain, Size: 1529 bytes --]
On 06/02/2016 02:52 AM, Greg Kurz wrote:
> This patch changes the 9p code to use readdir() again instead of
> readdir_r(), which is deprecated in glibc 2.24.
>
> All the locking was put in place by a previous patch.
>
> Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
> ---
> +++ b/hw/9pfs/codir.c
> @@ -17,8 +17,7 @@
> #include "qemu/coroutine.h"
> #include "coth.h"
>
> -int v9fs_co_readdir_r(V9fsPDU *pdu, V9fsFidState *fidp, struct dirent *dent,
> - struct dirent **result)
> +int v9fs_co_readdir(V9fsPDU *pdu, V9fsFidState *fidp, struct dirent **dent)
> {
> int err;
> V9fsState *s = pdu->s;
> @@ -28,11 +27,14 @@ int v9fs_co_readdir_r(V9fsPDU *pdu, V9fsFidState *fidp, struct dirent *dent,
> }
> v9fs_co_run_in_worker(
> {
> - errno = 0;
> - err = s->ops->readdir_r(&s->ctx, &fidp->fs, dent, result);
> - if (!*result && errno) {
> + struct dirent *entry;
> + int old_errno = errno;
> +
> + entry = s->ops->readdir(&s->ctx, &fidp->fs);
> + if (!entry && errno != old_errno) {
> err = -errno;
Not safe. The only safe way to check errno after readdir() is to assign
it to 0 before readdir().
> } else {
> + *dent = entry;
> err = 0;
> }
> });
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 604 bytes --]
^ permalink raw reply [flat|nested] 15+ messages in thread* Re: [Qemu-devel] [PATCH 4/4] 9p: switch back to readdir()
2016-06-02 21:00 ` Eric Blake
@ 2016-06-03 6:29 ` Greg Kurz
0 siblings, 0 replies; 15+ messages in thread
From: Greg Kurz @ 2016-06-03 6:29 UTC (permalink / raw)
To: Eric Blake; +Cc: Aneesh Kumar K.V, qemu-devel
On Thu, 2 Jun 2016 15:00:26 -0600
Eric Blake <eblake@redhat.com> wrote:
> On 06/02/2016 02:52 AM, Greg Kurz wrote:
> > This patch changes the 9p code to use readdir() again instead of
> > readdir_r(), which is deprecated in glibc 2.24.
> >
> > All the locking was put in place by a previous patch.
> >
> > Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
> > ---
>
>
> > +++ b/hw/9pfs/codir.c
> > @@ -17,8 +17,7 @@
> > #include "qemu/coroutine.h"
> > #include "coth.h"
> >
> > -int v9fs_co_readdir_r(V9fsPDU *pdu, V9fsFidState *fidp, struct dirent *dent,
> > - struct dirent **result)
> > +int v9fs_co_readdir(V9fsPDU *pdu, V9fsFidState *fidp, struct dirent **dent)
> > {
> > int err;
> > V9fsState *s = pdu->s;
> > @@ -28,11 +27,14 @@ int v9fs_co_readdir_r(V9fsPDU *pdu, V9fsFidState *fidp, struct dirent *dent,
> > }
> > v9fs_co_run_in_worker(
> > {
> > - errno = 0;
> > - err = s->ops->readdir_r(&s->ctx, &fidp->fs, dent, result);
> > - if (!*result && errno) {
> > + struct dirent *entry;
> > + int old_errno = errno;
> > +
> > + entry = s->ops->readdir(&s->ctx, &fidp->fs);
> > + if (!entry && errno != old_errno) {
> > err = -errno;
>
> Not safe. The only safe way to check errno after readdir() is to assign
> it to 0 before readdir().
>
Yeah, you're right, errno could already be set to one of the values
returned by readdir() in case of error...
> > } else {
> > + *dent = entry;
> > err = 0;
> > }
> > });
>
>
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [Qemu-devel] [PATCH 0/4] 9p: get rid of readdir_r()
2016-06-02 8:51 [Qemu-devel] [PATCH 0/4] 9p: get rid of readdir_r() Greg Kurz
` (3 preceding siblings ...)
2016-06-02 8:52 ` [Qemu-devel] [PATCH 4/4] 9p: switch back to readdir() Greg Kurz
@ 2016-06-02 9:33 ` Peter Maydell
2016-06-02 9:42 ` Greg Kurz
4 siblings, 1 reply; 15+ messages in thread
From: Peter Maydell @ 2016-06-02 9:33 UTC (permalink / raw)
To: Greg Kurz; +Cc: Aneesh Kumar K.V, QEMU Developers
On 2 June 2016 at 09:51, Greg Kurz <gkurz@linux.vnet.ibm.com> wrote:
> The readdir_r() function has a broken design and should not be used anymore.
> It is expected to be obsoleted in a future version of POSIX.1:
>
> http://austingroupbugs.net/view.php?id=696#c2857
>
> Glibc has already announced that 2.24 (scheduled for August 2016) will
> deprecates readdir_r() and encourages people to use readdir() with
> external synchronization instead.
> Since POSIX.1 will require readdir() to be thread-safe when employed on
> different directory streams, and glibc already does that, the choice
> was made to have per-directory locking.
AIUI the argument is that all sensible implementations of readdir()
already provide the thread-safety guarantees POSIX is going to
specify, but have you tested this on one of the BSDs or OSX?
(and/or checked their current readdir implementation...)
thanks
-- PMM
^ permalink raw reply [flat|nested] 15+ messages in thread* Re: [Qemu-devel] [PATCH 0/4] 9p: get rid of readdir_r()
2016-06-02 9:33 ` [Qemu-devel] [PATCH 0/4] 9p: get rid of readdir_r() Peter Maydell
@ 2016-06-02 9:42 ` Greg Kurz
2016-06-02 12:05 ` Peter Maydell
2016-06-02 13:59 ` Michael Fritscher
0 siblings, 2 replies; 15+ messages in thread
From: Greg Kurz @ 2016-06-02 9:42 UTC (permalink / raw)
To: Peter Maydell; +Cc: Aneesh Kumar K.V, QEMU Developers, Michael Fritscher
On Thu, 2 Jun 2016 10:33:06 +0100
Peter Maydell <peter.maydell@linaro.org> wrote:
> On 2 June 2016 at 09:51, Greg Kurz <gkurz@linux.vnet.ibm.com> wrote:
> > The readdir_r() function has a broken design and should not be used anymore.
> > It is expected to be obsoleted in a future version of POSIX.1:
> >
> > http://austingroupbugs.net/view.php?id=696#c2857
> >
> > Glibc has already announced that 2.24 (scheduled for August 2016) will
> > deprecates readdir_r() and encourages people to use readdir() with
> > external synchronization instead.
>
> > Since POSIX.1 will require readdir() to be thread-safe when employed on
> > different directory streams, and glibc already does that, the choice
> > was made to have per-directory locking.
>
> AIUI the argument is that all sensible implementations of readdir()
> already provide the thread-safety guarantees POSIX is going to
> specify, but have you tested this on one of the BSDs or OSX?
> (and/or checked their current readdir implementation...)
>
No I haven't because "VirtFS is supported only on Linux" at the moment.
But thanks for raising the flag: it reminds me that there's ongoing
work to support VirtFS on win32 hosts and I should also Cc Michael
Fritscher.
Thanks !
--
Greg
> thanks
> -- PMM
>
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [Qemu-devel] [PATCH 0/4] 9p: get rid of readdir_r()
2016-06-02 9:42 ` Greg Kurz
@ 2016-06-02 12:05 ` Peter Maydell
2016-06-02 13:59 ` Michael Fritscher
1 sibling, 0 replies; 15+ messages in thread
From: Peter Maydell @ 2016-06-02 12:05 UTC (permalink / raw)
To: Greg Kurz; +Cc: Aneesh Kumar K.V, QEMU Developers, Michael Fritscher
On 2 June 2016 at 10:42, Greg Kurz <gkurz@linux.vnet.ibm.com> wrote:
> On Thu, 2 Jun 2016 10:33:06 +0100
> Peter Maydell <peter.maydell@linaro.org> wrote:
>> AIUI the argument is that all sensible implementations of readdir()
>> already provide the thread-safety guarantees POSIX is going to
>> specify, but have you tested this on one of the BSDs or OSX?
>> (and/or checked their current readdir implementation...)
> No I haven't because "VirtFS is supported only on Linux" at the moment.
Ah, so it is, I hadn't noticed we disabled it in configure for
non-Linux hosts.
thanks
-- PMM
^ permalink raw reply [flat|nested] 15+ messages in thread
* Re: [Qemu-devel] [PATCH 0/4] 9p: get rid of readdir_r()
2016-06-02 9:42 ` Greg Kurz
2016-06-02 12:05 ` Peter Maydell
@ 2016-06-02 13:59 ` Michael Fritscher
2016-06-02 15:47 ` Greg Kurz
1 sibling, 1 reply; 15+ messages in thread
From: Michael Fritscher @ 2016-06-02 13:59 UTC (permalink / raw)
To: Greg Kurz, Peter Maydell; +Cc: Aneesh Kumar K.V, QEMU Developers
[-- Attachment #1.1: Type: text/plain, Size: 4655 bytes --]
Am 02.06.2016 um 11:42 schrieb Greg Kurz:
> On Thu, 2 Jun 2016 10:33:06 +0100
> Peter Maydell <peter.maydell@linaro.org> wrote:
>
>> On 2 June 2016 at 09:51, Greg Kurz <gkurz@linux.vnet.ibm.com> wrote:
>>> The readdir_r() function has a broken design and should not be used anymore.
>>> It is expected to be obsoleted in a future version of POSIX.1:
>>>
>>> http://austingroupbugs.net/view.php?id=696#c2857
>>>
>>> Glibc has already announced that 2.24 (scheduled for August 2016) will
>>> deprecates readdir_r() and encourages people to use readdir() with
>>> external synchronization instead.
>>
>>> Since POSIX.1 will require readdir() to be thread-safe when employed on
>>> different directory streams, and glibc already does that, the choice
>>> was made to have per-directory locking.
>>
>> AIUI the argument is that all sensible implementations of readdir()
>> already provide the thread-safety guarantees POSIX is going to
>> specify, but have you tested this on one of the BSDs or OSX?
>> (and/or checked their current readdir implementation...)
>>
>
> No I haven't because "VirtFS is supported only on Linux" at the moment.
>
> But thanks for raising the flag: it reminds me that there's ongoing
> work to support VirtFS on win32 hosts and I should also Cc Michael
> Fritscher.
Hi,
thanks for CCing me!
I've digged a bit about the readdir<89 problem.
Following question: So we should relay on the thread safeness on
readdir() in the case of different directory streams?
I looked into the MingW implementation of it (see below). If I see it
correctly it seems to be threadsafe on the case of different directory
streams as well. But I didn't found any info about whether findfirst is
- but no warning regarding it on the MSDN
(https://msdn.microsoft.com/en-us/library/6tkkkc1y.aspx)
It is clearly NOT threadsafe using it on the same dir stream.
I think we need to lock based on the pointer saved in V9fsFidOpenState
fs->dir . Do we have a way to archive something like this:
lock(fs->dir); //if there is already a lock named the address stored in
fs->dir then wait
readdir(fs_dir,...);
unlock(fs->dir);
? Else we would have to track all the fs->dir, which is a bit of work
I'm afraid (some kind of hashset or similiar would be usefull then)...
Best regards,
Michael Fritscher
/*
* readdir
*
* Return a pointer to a dirent structure filled with the information
on the
* next entry in the directory.
*/
struct _tdirent *
_treaddir (_TDIR * dirp)
{
errno = 0;
/* Check for valid DIR struct. */
if (!dirp)
{
errno = EFAULT;
return (struct _tdirent *) 0;
}
if (dirp->dd_stat < 0)
{
/* We have already returned all files in the directory
* (or the structure has an invalid dd_stat). */
return (struct _tdirent *) 0;
}
else if (dirp->dd_stat == 0)
{
/* We haven't started the search yet. */
/* Start the search */
dirp->dd_handle = _tfindfirst (dirp->dd_name, &(dirp->dd_dta));
if (dirp->dd_handle == -1)
{
/* Whoops! Seems there are no files in that
* directory. */
dirp->dd_stat = -1;
}
else
{
dirp->dd_stat = 1;
}
}
else
{
/* Get the next search entry. */
if (_tfindnext (dirp->dd_handle, &(dirp->dd_dta)))
{
/* We are off the end or otherwise error.
_findnext sets errno to ENOENT if no more file
Undo this. */
DWORD winerr = GetLastError ();
if (winerr == ERROR_NO_MORE_FILES)
errno = 0;
_findclose (dirp->dd_handle);
dirp->dd_handle = -1;
dirp->dd_stat = -1;
}
else
{
/* Update the status to indicate the correct
* number. */
dirp->dd_stat++;
}
}
if (dirp->dd_stat > 0)
{
/* Successfully got an entry. Everything about the file is
* already appropriately filled in except the length of the
* file name. */
dirp->dd_dir.d_namlen = _tcslen (dirp->dd_dta.name);
_tcscpy (dirp->dd_dir.d_name, dirp->dd_dta.name);
return &dirp->dd_dir;
}
return (struct _tdirent *) 0;
}
--
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email;internet:michael.fritscher@telematik-zentrum.de
tel;work:+49 (931) 3 29 29 54 - 21
tel;fax:+49 (931) 3 29 29 54 - 11
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^ permalink raw reply [flat|nested] 15+ messages in thread* Re: [Qemu-devel] [PATCH 0/4] 9p: get rid of readdir_r()
2016-06-02 13:59 ` Michael Fritscher
@ 2016-06-02 15:47 ` Greg Kurz
0 siblings, 0 replies; 15+ messages in thread
From: Greg Kurz @ 2016-06-02 15:47 UTC (permalink / raw)
To: Michael Fritscher; +Cc: Peter Maydell, Aneesh Kumar K.V, QEMU Developers
On Thu, 2 Jun 2016 15:59:29 +0200
Michael Fritscher <michael.fritscher@telematik-zentrum.de> wrote:
> Am 02.06.2016 um 11:42 schrieb Greg Kurz:
> > On Thu, 2 Jun 2016 10:33:06 +0100
> > Peter Maydell <peter.maydell@linaro.org> wrote:
> >
> >> On 2 June 2016 at 09:51, Greg Kurz <gkurz@linux.vnet.ibm.com> wrote:
> >>> The readdir_r() function has a broken design and should not be used anymore.
> >>> It is expected to be obsoleted in a future version of POSIX.1:
> >>>
> >>> http://austingroupbugs.net/view.php?id=696#c2857
> >>>
> >>> Glibc has already announced that 2.24 (scheduled for August 2016) will
> >>> deprecates readdir_r() and encourages people to use readdir() with
> >>> external synchronization instead.
> >>
> >>> Since POSIX.1 will require readdir() to be thread-safe when employed on
> >>> different directory streams, and glibc already does that, the choice
> >>> was made to have per-directory locking.
> >>
> >> AIUI the argument is that all sensible implementations of readdir()
> >> already provide the thread-safety guarantees POSIX is going to
> >> specify, but have you tested this on one of the BSDs or OSX?
> >> (and/or checked their current readdir implementation...)
> >>
> >
> > No I haven't because "VirtFS is supported only on Linux" at the moment.
> >
> > But thanks for raising the flag: it reminds me that there's ongoing
> > work to support VirtFS on win32 hosts and I should also Cc Michael
> > Fritscher.
>
> Hi,
> thanks for CCing me!
>
Hi Michael !
> I've digged a bit about the readdir<89 problem.
> Following question: So we should relay on the thread safeness on
> readdir() in the case of different directory streams?
>
> I looked into the MingW implementation of it (see below). If I see it
> correctly it seems to be threadsafe on the case of different directory
> streams as well.
Cool.
> But I didn't found any info about whether findfirst is
> - but no warning regarding it on the MSDN
> (https://msdn.microsoft.com/en-us/library/6tkkkc1y.aspx)
>
Heh the windows API is a bit similar to readdir_r(): the caller
has a handle to pass to all find* calls. So it is likely to
be reentrant, but we would need to see the source to be sure ;)
> It is clearly NOT threadsafe using it on the same dir stream.
>
> I think we need to lock based on the pointer saved in V9fsFidOpenState
> fs->dir . Do we have a way to archive something like this:
>
> lock(fs->dir); //if there is already a lock named the address stored in
> fs->dir then wait
> readdir(fs_dir,...);
> unlock(fs->dir);
>
> ? Else we would have to track all the fs->dir, which is a bit of work
> I'm afraid (some kind of hashset or similiar would be usefull then)...
>
This series gets rid of readdir_r() completely and already addresses all
the locking around critical sections. So you don't have to implement your
own version of readdir_r() anymore.
Maybe you can rebase your patchset against:
https://github.com/gkurz/qemu.git 9p-next
Cheers.
--
Greg
> Best regards,
> Michael Fritscher
>
> /*
> * readdir
> *
> * Return a pointer to a dirent structure filled with the information
> on the
> * next entry in the directory.
> */
> struct _tdirent *
> _treaddir (_TDIR * dirp)
> {
> errno = 0;
>
> /* Check for valid DIR struct. */
> if (!dirp)
> {
> errno = EFAULT;
> return (struct _tdirent *) 0;
> }
>
> if (dirp->dd_stat < 0)
> {
> /* We have already returned all files in the directory
> * (or the structure has an invalid dd_stat). */
> return (struct _tdirent *) 0;
> }
> else if (dirp->dd_stat == 0)
> {
> /* We haven't started the search yet. */
> /* Start the search */
> dirp->dd_handle = _tfindfirst (dirp->dd_name, &(dirp->dd_dta));
>
> if (dirp->dd_handle == -1)
> {
> /* Whoops! Seems there are no files in that
> * directory. */
> dirp->dd_stat = -1;
> }
> else
> {
> dirp->dd_stat = 1;
> }
> }
> else
> {
> /* Get the next search entry. */
> if (_tfindnext (dirp->dd_handle, &(dirp->dd_dta)))
> {
> /* We are off the end or otherwise error.
> _findnext sets errno to ENOENT if no more file
> Undo this. */
> DWORD winerr = GetLastError ();
> if (winerr == ERROR_NO_MORE_FILES)
> errno = 0;
> _findclose (dirp->dd_handle);
> dirp->dd_handle = -1;
> dirp->dd_stat = -1;
> }
> else
> {
> /* Update the status to indicate the correct
> * number. */
> dirp->dd_stat++;
> }
> }
>
> if (dirp->dd_stat > 0)
> {
> /* Successfully got an entry. Everything about the file is
> * already appropriately filled in except the length of the
> * file name. */
> dirp->dd_dir.d_namlen = _tcslen (dirp->dd_dta.name);
> _tcscpy (dirp->dd_dir.d_name, dirp->dd_dta.name);
> return &dirp->dd_dir;
> }
>
> return (struct _tdirent *) 0;
> }
>
^ permalink raw reply [flat|nested] 15+ messages in thread