Add a getsize() function pointer to struct hypfs_funcs for being able
to have dynamically filled entries without the need to take the hypfs
lock each time the contents are being generated.
For directories add a findentry callback to the vector and modify
hypfs_get_entry_rel() to use it.
Signed-off-by: Juergen Gross <jgross@suse.com>
---
V2:
- add a dummy findentry function (Jan Beulich)
- add const to findentry dir parameter
- don't move DIRENTRY_SIZE() to hypfs.h (Jan Beulich)
- split dyndir support off into new patch
Signed-off-by: Juergen Gross <jgross@suse.com>
---
xen/common/hypfs.c | 100 ++++++++++++++++++++++++++--------------
xen/include/xen/hypfs.h | 25 +++++++++-
2 files changed, 89 insertions(+), 36 deletions(-)
diff --git a/xen/common/hypfs.c b/xen/common/hypfs.c
index fdfd0f764a..83c5cacdca 100644
--- a/xen/common/hypfs.c
+++ b/xen/common/hypfs.c
@@ -27,22 +27,32 @@ CHECK_hypfs_dirlistentry;
const struct hypfs_funcs hypfs_dir_funcs = {
.read = hypfs_read_dir,
.write = hypfs_write_deny,
+ .getsize = hypfs_getsize,
+ .findentry = hypfs_dir_findentry,
};
const struct hypfs_funcs hypfs_leaf_ro_funcs = {
.read = hypfs_read_leaf,
.write = hypfs_write_deny,
+ .getsize = hypfs_getsize,
+ .findentry = hypfs_leaf_findentry,
};
const struct hypfs_funcs hypfs_leaf_wr_funcs = {
.read = hypfs_read_leaf,
.write = hypfs_write_leaf,
+ .getsize = hypfs_getsize,
+ .findentry = hypfs_leaf_findentry,
};
const struct hypfs_funcs hypfs_bool_wr_funcs = {
.read = hypfs_read_leaf,
.write = hypfs_write_bool,
+ .getsize = hypfs_getsize,
+ .findentry = hypfs_leaf_findentry,
};
const struct hypfs_funcs hypfs_custom_wr_funcs = {
.read = hypfs_read_leaf,
.write = hypfs_write_custom,
+ .getsize = hypfs_getsize,
+ .findentry = hypfs_leaf_findentry,
};
static DEFINE_RWLOCK(hypfs_lock);
@@ -97,6 +107,8 @@ static int add_entry(struct hypfs_entry_dir *parent, struct hypfs_entry *new)
ASSERT(new->funcs->read);
ASSERT(new->funcs->write);
+ ASSERT(new->funcs->getsize);
+ ASSERT(new->funcs->findentry);
hypfs_write_lock();
@@ -176,15 +188,41 @@ static int hypfs_get_path_user(char *buf,
return 0;
}
+struct hypfs_entry *hypfs_leaf_findentry(const struct hypfs_entry_dir *dir,
+ const char *name,
+ unsigned int name_len)
+{
+ return ERR_PTR(-ENOENT);
+}
+
+struct hypfs_entry *hypfs_dir_findentry(const struct hypfs_entry_dir *dir,
+ const char *name,
+ unsigned int name_len)
+{
+ struct hypfs_entry *entry;
+
+ list_for_each_entry ( entry, &dir->dirlist, list )
+ {
+ int cmp = strncmp(name, entry->name, name_len);
+
+ if ( cmp < 0 )
+ return ERR_PTR(-ENOENT);
+
+ if ( !cmp && strlen(entry->name) == name_len )
+ return entry;
+ }
+
+ return ERR_PTR(-ENOENT);
+}
+
static struct hypfs_entry *hypfs_get_entry_rel(struct hypfs_entry_dir *dir,
const char *path)
{
const char *end;
struct hypfs_entry *entry;
unsigned int name_len;
- bool again = true;
- while ( again )
+ for ( ; ; )
{
if ( dir->e.type != XEN_HYPFS_TYPE_DIR )
return ERR_PTR(-ENOENT);
@@ -197,28 +235,12 @@ static struct hypfs_entry *hypfs_get_entry_rel(struct hypfs_entry_dir *dir,
end = strchr(path, '\0');
name_len = end - path;
- again = false;
+ entry = dir->e.funcs->findentry(dir, path, name_len);
+ if ( IS_ERR(entry) || !*end )
+ return entry;
- list_for_each_entry ( entry, &dir->dirlist, list )
- {
- int cmp = strncmp(path, entry->name, name_len);
- struct hypfs_entry_dir *d = container_of(entry,
- struct hypfs_entry_dir, e);
-
- if ( cmp < 0 )
- return ERR_PTR(-ENOENT);
- if ( !cmp && strlen(entry->name) == name_len )
- {
- if ( !*end )
- return entry;
-
- again = true;
- dir = d;
- path = end + 1;
-
- break;
- }
- }
+ path = end + 1;
+ dir = container_of(entry, struct hypfs_entry_dir, e);
}
return ERR_PTR(-ENOENT);
@@ -232,12 +254,17 @@ static struct hypfs_entry *hypfs_get_entry(const char *path)
return hypfs_get_entry_rel(&hypfs_root, path + 1);
}
+unsigned int hypfs_getsize(const struct hypfs_entry *entry)
+{
+ return entry->size;
+}
+
int hypfs_read_dir(const struct hypfs_entry *entry,
XEN_GUEST_HANDLE_PARAM(void) uaddr)
{
const struct hypfs_entry_dir *d;
const struct hypfs_entry *e;
- unsigned int size = entry->size;
+ unsigned int size = entry->funcs->getsize(entry);
ASSERT(this_cpu(hypfs_locked) != hypfs_unlocked);
@@ -252,7 +279,7 @@ int hypfs_read_dir(const struct hypfs_entry *entry,
direntry.e.pad = 0;
direntry.e.type = e->type;
direntry.e.encoding = e->encoding;
- direntry.e.content_len = e->size;
+ direntry.e.content_len = e->funcs->getsize(e);
direntry.e.max_write_len = e->max_size;
direntry.off_next = list_is_last(&e->list, &d->dirlist) ? 0 : e_len;
if ( copy_to_guest(uaddr, &direntry, 1) )
@@ -275,18 +302,20 @@ int hypfs_read_leaf(const struct hypfs_entry *entry,
XEN_GUEST_HANDLE_PARAM(void) uaddr)
{
const struct hypfs_entry_leaf *l;
+ unsigned int size = entry->funcs->getsize(entry);
ASSERT(this_cpu(hypfs_locked) != hypfs_unlocked);
l = container_of(entry, const struct hypfs_entry_leaf, e);
- return copy_to_guest(uaddr, l->u.content, entry->size) ? -EFAULT: 0;
+ return copy_to_guest(uaddr, l->u.content, size) ? -EFAULT : 0;
}
static int hypfs_read(const struct hypfs_entry *entry,
XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned long ulen)
{
struct xen_hypfs_direntry e;
+ unsigned int size = entry->funcs->getsize(entry);
long ret = -EINVAL;
if ( ulen < sizeof(e) )
@@ -295,7 +324,7 @@ static int hypfs_read(const struct hypfs_entry *entry,
e.pad = 0;
e.type = entry->type;
e.encoding = entry->encoding;
- e.content_len = entry->size;
+ e.content_len = size;
e.max_write_len = entry->max_size;
ret = -EFAULT;
@@ -303,7 +332,7 @@ static int hypfs_read(const struct hypfs_entry *entry,
goto out;
ret = -ENOBUFS;
- if ( ulen < entry->size + sizeof(e) )
+ if ( ulen < size + sizeof(e) )
goto out;
guest_handle_add_offset(uaddr, sizeof(e));
@@ -319,15 +348,16 @@ int hypfs_write_leaf(struct hypfs_entry_leaf *leaf,
{
char *buf;
int ret;
+ struct hypfs_entry *e = &leaf->e;
ASSERT(this_cpu(hypfs_locked) == hypfs_write_locked);
ASSERT(leaf->e.max_size);
- if ( ulen > leaf->e.max_size )
+ if ( ulen > e->max_size )
return -ENOSPC;
- if ( leaf->e.type != XEN_HYPFS_TYPE_STRING &&
- leaf->e.type != XEN_HYPFS_TYPE_BLOB && ulen != leaf->e.size )
+ if ( e->type != XEN_HYPFS_TYPE_STRING &&
+ e->type != XEN_HYPFS_TYPE_BLOB && ulen != e->funcs->getsize(e) )
return -EDOM;
buf = xmalloc_array(char, ulen);
@@ -339,14 +369,14 @@ int hypfs_write_leaf(struct hypfs_entry_leaf *leaf,
goto out;
ret = -EINVAL;
- if ( leaf->e.type == XEN_HYPFS_TYPE_STRING &&
- leaf->e.encoding == XEN_HYPFS_ENC_PLAIN &&
+ if ( e->type == XEN_HYPFS_TYPE_STRING &&
+ e->encoding == XEN_HYPFS_ENC_PLAIN &&
memchr(buf, 0, ulen) != (buf + ulen - 1) )
goto out;
ret = 0;
memcpy(leaf->u.write_ptr, buf, ulen);
- leaf->e.size = ulen;
+ e->size = ulen;
out:
xfree(buf);
@@ -360,7 +390,7 @@ int hypfs_write_bool(struct hypfs_entry_leaf *leaf,
ASSERT(this_cpu(hypfs_locked) == hypfs_write_locked);
ASSERT(leaf->e.type == XEN_HYPFS_TYPE_BOOL &&
- leaf->e.size == sizeof(bool) &&
+ leaf->e.funcs->getsize(&leaf->e) == sizeof(bool) &&
leaf->e.max_size == sizeof(bool) );
if ( ulen != leaf->e.max_size )
diff --git a/xen/include/xen/hypfs.h b/xen/include/xen/hypfs.h
index 25fdf3ead7..53f50772b4 100644
--- a/xen/include/xen/hypfs.h
+++ b/xen/include/xen/hypfs.h
@@ -2,17 +2,21 @@
#define __XEN_HYPFS_H__
#ifdef CONFIG_HYPFS
+#include <xen/lib.h>
#include <xen/list.h>
#include <xen/string.h>
#include <public/hypfs.h>
struct hypfs_entry_leaf;
+struct hypfs_entry_dir;
struct hypfs_entry;
/*
* Per-node callbacks:
*
- * The callbacks are always called with the hypfs lock held.
+ * The callbacks are always called with the hypfs lock held. In case multiple
+ * callbacks are called for a single operation the lock is held across all
+ * those callbacks.
*
* The read() callback is used to return the contents of a node (either
* directory or leaf). It is NOT used to get directory entries during traversal
@@ -20,12 +24,24 @@ struct hypfs_entry;
*
* The write() callback is used to modify the contents of a node. Writing
* directories is not supported (this means all nodes are added at boot time).
+ *
+ * getsize() is called in two cases:
+ * - when reading a node (directory or leaf) for filling in the size of the
+ * node into the returned direntry
+ * - when reading a directory for each node in this directory
+ *
+ * findentry() is called for traversing a path from the root node to a node
+ * for all nodes on that path excluding the final node (so for looking up
+ * "/a/b/c" findentry() will be called for "/", "/a", and "/a/b").
*/
struct hypfs_funcs {
int (*read)(const struct hypfs_entry *entry,
XEN_GUEST_HANDLE_PARAM(void) uaddr);
int (*write)(struct hypfs_entry_leaf *leaf,
XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned int ulen);
+ unsigned int (*getsize)(const struct hypfs_entry *entry);
+ struct hypfs_entry *(*findentry)(const struct hypfs_entry_dir *dir,
+ const char *name, unsigned int name_len);
};
extern const struct hypfs_funcs hypfs_dir_funcs;
@@ -145,6 +161,13 @@ int hypfs_write_bool(struct hypfs_entry_leaf *leaf,
XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned int ulen);
int hypfs_write_custom(struct hypfs_entry_leaf *leaf,
XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned int ulen);
+unsigned int hypfs_getsize(const struct hypfs_entry *entry);
+struct hypfs_entry *hypfs_leaf_findentry(const struct hypfs_entry_dir *dir,
+ const char *name,
+ unsigned int name_len);
+struct hypfs_entry *hypfs_dir_findentry(const struct hypfs_entry_dir *dir,
+ const char *name,
+ unsigned int name_len);
#endif
#endif /* __XEN_HYPFS_H__ */
--
2.26.2
On 01.12.2020 09:21, Juergen Gross wrote:
> Add a getsize() function pointer to struct hypfs_funcs for being able
> to have dynamically filled entries without the need to take the hypfs
> lock each time the contents are being generated.
>
> For directories add a findentry callback to the vector and modify
> hypfs_get_entry_rel() to use it.
>
> Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
with maybe one further small adjustment:
> @@ -176,15 +188,41 @@ static int hypfs_get_path_user(char *buf,
> return 0;
> }
>
> +struct hypfs_entry *hypfs_leaf_findentry(const struct hypfs_entry_dir *dir,
> + const char *name,
> + unsigned int name_len)
> +{
> + return ERR_PTR(-ENOENT);
> +}
ENOENT seems odd to me here. There looks to be no counterpart to
EISDIR, so maybe ENODATA, EACCES, or EPERM?
Jan
On 02.12.20 16:42, Jan Beulich wrote:
> On 01.12.2020 09:21, Juergen Gross wrote:
>> Add a getsize() function pointer to struct hypfs_funcs for being able
>> to have dynamically filled entries without the need to take the hypfs
>> lock each time the contents are being generated.
>>
>> For directories add a findentry callback to the vector and modify
>> hypfs_get_entry_rel() to use it.
>>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>
> Reviewed-by: Jan Beulich <jbeulich@suse.com>
> with maybe one further small adjustment:
>
>> @@ -176,15 +188,41 @@ static int hypfs_get_path_user(char *buf,
>> return 0;
>> }
>>
>> +struct hypfs_entry *hypfs_leaf_findentry(const struct hypfs_entry_dir *dir,
>> + const char *name,
>> + unsigned int name_len)
>> +{
>> + return ERR_PTR(-ENOENT);
>> +}
>
> ENOENT seems odd to me here. There looks to be no counterpart to
> EISDIR, so maybe ENODATA, EACCES, or EPERM?
Hmm, why?
In case I have /a/b and I'm looking for /a/b/c ENOENT seems to be just
fine?
Or I could add ENOTDIR.
Juergen
On 02.12.2020 16:51, Jürgen Groß wrote:
> On 02.12.20 16:42, Jan Beulich wrote:
>> On 01.12.2020 09:21, Juergen Gross wrote:
>>> Add a getsize() function pointer to struct hypfs_funcs for being able
>>> to have dynamically filled entries without the need to take the hypfs
>>> lock each time the contents are being generated.
>>>
>>> For directories add a findentry callback to the vector and modify
>>> hypfs_get_entry_rel() to use it.
>>>
>>> Signed-off-by: Juergen Gross <jgross@suse.com>
>>
>> Reviewed-by: Jan Beulich <jbeulich@suse.com>
>> with maybe one further small adjustment:
>>
>>> @@ -176,15 +188,41 @@ static int hypfs_get_path_user(char *buf,
>>> return 0;
>>> }
>>>
>>> +struct hypfs_entry *hypfs_leaf_findentry(const struct hypfs_entry_dir *dir,
>>> + const char *name,
>>> + unsigned int name_len)
>>> +{
>>> + return ERR_PTR(-ENOENT);
>>> +}
>>
>> ENOENT seems odd to me here. There looks to be no counterpart to
>> EISDIR, so maybe ENODATA, EACCES, or EPERM?
>
> Hmm, why?
>
> In case I have /a/b and I'm looking for /a/b/c ENOENT seems to be just
> fine?
>
> Or I could add ENOTDIR.
Oh, there actually is supposed to be such an entry, but public/errno.h
is simply missing it. Yes - ENOTDIR is what I was thinking of when
saying "there looks to be no counterpart to EISDIR".
Jan
On 03.12.20 09:12, Jan Beulich wrote:
> On 02.12.2020 16:51, Jürgen Groß wrote:
>> On 02.12.20 16:42, Jan Beulich wrote:
>>> On 01.12.2020 09:21, Juergen Gross wrote:
>>>> Add a getsize() function pointer to struct hypfs_funcs for being able
>>>> to have dynamically filled entries without the need to take the hypfs
>>>> lock each time the contents are being generated.
>>>>
>>>> For directories add a findentry callback to the vector and modify
>>>> hypfs_get_entry_rel() to use it.
>>>>
>>>> Signed-off-by: Juergen Gross <jgross@suse.com>
>>>
>>> Reviewed-by: Jan Beulich <jbeulich@suse.com>
>>> with maybe one further small adjustment:
>>>
>>>> @@ -176,15 +188,41 @@ static int hypfs_get_path_user(char *buf,
>>>> return 0;
>>>> }
>>>>
>>>> +struct hypfs_entry *hypfs_leaf_findentry(const struct hypfs_entry_dir *dir,
>>>> + const char *name,
>>>> + unsigned int name_len)
>>>> +{
>>>> + return ERR_PTR(-ENOENT);
>>>> +}
>>>
>>> ENOENT seems odd to me here. There looks to be no counterpart to
>>> EISDIR, so maybe ENODATA, EACCES, or EPERM?
>>
>> Hmm, why?
>>
>> In case I have /a/b and I'm looking for /a/b/c ENOENT seems to be just
>> fine?
>>
>> Or I could add ENOTDIR.
>
> Oh, there actually is supposed to be such an entry, but public/errno.h
> is simply missing it. Yes - ENOTDIR is what I was thinking of when
> saying "there looks to be no counterpart to EISDIR".
Okay, I'll add ENOTDIR and set it here.
Juergen
On 01.12.2020 09:21, Juergen Gross wrote:
> @@ -197,28 +235,12 @@ static struct hypfs_entry *hypfs_get_entry_rel(struct hypfs_entry_dir *dir,
> end = strchr(path, '\0');
> name_len = end - path;
>
> - again = false;
> + entry = dir->e.funcs->findentry(dir, path, name_len);
> + if ( IS_ERR(entry) || !*end )
> + return entry;
>
> - list_for_each_entry ( entry, &dir->dirlist, list )
> - {
> - int cmp = strncmp(path, entry->name, name_len);
> - struct hypfs_entry_dir *d = container_of(entry,
> - struct hypfs_entry_dir, e);
> -
> - if ( cmp < 0 )
> - return ERR_PTR(-ENOENT);
> - if ( !cmp && strlen(entry->name) == name_len )
> - {
> - if ( !*end )
> - return entry;
> -
> - again = true;
> - dir = d;
> - path = end + 1;
> -
> - break;
> - }
> - }
> + path = end + 1;
> + dir = container_of(entry, struct hypfs_entry_dir, e);
> }
Looking at patch 15 my understanding is that "dir" may get invalidated
by the call to the ->findentry() hook above. That is, use of dir has
to be avoided between the two calls. This isn't at all obvious, so I
wonder whether at least a comment wouldn't want adding to avoid future
mistakes.
And of course the same comment applies to the IS_ERR() use here vs NULL
coming back that I already gave for the ->enter() call site.
Jan
On 04.12.20 09:58, Jan Beulich wrote:
> On 01.12.2020 09:21, Juergen Gross wrote:
>> @@ -197,28 +235,12 @@ static struct hypfs_entry *hypfs_get_entry_rel(struct hypfs_entry_dir *dir,
>> end = strchr(path, '\0');
>> name_len = end - path;
>>
>> - again = false;
>> + entry = dir->e.funcs->findentry(dir, path, name_len);
>> + if ( IS_ERR(entry) || !*end )
>> + return entry;
>>
>> - list_for_each_entry ( entry, &dir->dirlist, list )
>> - {
>> - int cmp = strncmp(path, entry->name, name_len);
>> - struct hypfs_entry_dir *d = container_of(entry,
>> - struct hypfs_entry_dir, e);
>> -
>> - if ( cmp < 0 )
>> - return ERR_PTR(-ENOENT);
>> - if ( !cmp && strlen(entry->name) == name_len )
>> - {
>> - if ( !*end )
>> - return entry;
>> -
>> - again = true;
>> - dir = d;
>> - path = end + 1;
>> -
>> - break;
>> - }
>> - }
>> + path = end + 1;
>> + dir = container_of(entry, struct hypfs_entry_dir, e);
>> }
>
> Looking at patch 15 my understanding is that "dir" may get invalidated
> by the call to the ->findentry() hook above. That is, use of dir has
> to be avoided between the two calls. This isn't at all obvious, so I
> wonder whether at least a comment wouldn't want adding to avoid future
> mistakes.
Will add a comment.
>
> And of course the same comment applies to the IS_ERR() use here vs NULL
> coming back that I already gave for the ->enter() call site.
I'll add an ASSERT().
Juergen
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