* [PATCH] fs: Create anon_inode_getfile_fmode()
@ 2024-04-24 23:38 Dawid Osuchowski
2024-04-25 9:57 ` Christian Brauner
0 siblings, 1 reply; 6+ messages in thread
From: Dawid Osuchowski @ 2024-04-24 23:38 UTC (permalink / raw)
To: linux-fsdevel; +Cc: viro, brauner, jack, Dawid Osuchowski
Creates an anon_inode_getfile_fmode() function that works similarly to
anon_inode_getfile() with the addition of being able to set the fmode
member.
Signed-off-by: Dawid Osuchowski <linux@osuchow.ski>
---
fs/anon_inodes.c | 48 +++++++++++++++++++++++++++++++++++++
include/linux/anon_inodes.h | 3 +++
2 files changed, 51 insertions(+)
diff --git a/fs/anon_inodes.c b/fs/anon_inodes.c
index 0496cb5b6eab..6d61d7d1669a 100644
--- a/fs/anon_inodes.c
+++ b/fs/anon_inodes.c
@@ -148,6 +148,53 @@ struct file *anon_inode_getfile(const char *name,
}
EXPORT_SYMBOL_GPL(anon_inode_getfile);
+
+static struct file *__anon_inode_getfile_fmode(const char *name,
+ const struct file_operations *fops,
+ void *priv, int flags, fmode_t f_mode)
+{
+
+ struct file *file;
+
+ file = __anon_inode_getfile(name, fops, priv, flags, NULL, false);
+ if (IS_ERR(file))
+ goto err;
+
+ file->f_mode |= f_mode;
+
+ return file;
+
+err:
+ return file;
+}
+
+/**
+ * anon_inode_getfile_fmode - creates a new file instance by hooking it up to an
+ * anonymous inode, and a dentry that describe the "class"
+ * of the file
+ *
+ * @name: [in] name of the "class" of the new file
+ * @fops: [in] file operations for the new file
+ * @priv: [in] private data for the new file (will be file's private_data)
+ * @flags: [in] flags
+ * @f_mode: [in] fmode
+ *
+ * Creates a new file by hooking it on a single inode. This is useful for files
+ * that do not need to have a full-fledged inode in order to operate correctly.
+ * All the files created with anon_inode_getfile() will share a single inode,
+ * hence saving memory and avoiding code duplication for the file/inode/dentry
+ * setup. Allows setting the fmode. Returns the newly created file* or an error
+ * pointer.
+ */
+struct file *anon_inode_getfile_fmode(const char *name,
+ const struct file_operations *fops,
+ void *priv, int flags, fmode_t f_mode)
+{
+ return __anon_inode_getfile_fmode(name, fops, priv,
+ flags, f_mode);
+}
+EXPORT_SYMBOL_GPL(anon_inode_getfile_fmode);
+
/**
* anon_inode_create_getfile - Like anon_inode_getfile(), but creates a new
* !S_PRIVATE anon inode rather than reuse the
@@ -271,6 +318,7 @@ int anon_inode_create_getfd(const char *name, const struct file_operations *fops
return __anon_inode_getfd(name, fops, priv, flags, context_inode, true);
}
+
static int __init anon_inode_init(void)
{
anon_inode_mnt = kern_mount(&anon_inode_fs_type);
diff --git a/include/linux/anon_inodes.h b/include/linux/anon_inodes.h
index 93a5f16d03f3..ee55f9c11a16 100644
--- a/include/linux/anon_inodes.h
+++ b/include/linux/anon_inodes.h
@@ -15,6 +15,9 @@ struct inode;
struct file *anon_inode_getfile(const char *name,
const struct file_operations *fops,
void *priv, int flags);
+struct file *anon_inode_getfile_fmode(const char *name,
+ const struct file_operations *fops,
+ void *priv, int flags, unsigned int f_mode);
struct file *anon_inode_create_getfile(const char *name,
const struct file_operations *fops,
void *priv, int flags,
--
2.44.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] fs: Create anon_inode_getfile_fmode()
2024-04-24 23:38 [PATCH] fs: Create anon_inode_getfile_fmode() Dawid Osuchowski
@ 2024-04-25 9:57 ` Christian Brauner
2024-04-25 10:13 ` Dawid Osuchowski
2024-04-25 20:25 ` Al Viro
0 siblings, 2 replies; 6+ messages in thread
From: Christian Brauner @ 2024-04-25 9:57 UTC (permalink / raw)
To: Dawid Osuchowski; +Cc: linux-fsdevel, viro, jack
On Thu, Apr 25, 2024 at 01:38:59AM +0200, Dawid Osuchowski wrote:
> Creates an anon_inode_getfile_fmode() function that works similarly to
> anon_inode_getfile() with the addition of being able to set the fmode
> member.
And for what use-case exactly?
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] fs: Create anon_inode_getfile_fmode()
2024-04-25 9:57 ` Christian Brauner
@ 2024-04-25 10:13 ` Dawid Osuchowski
2024-04-25 20:25 ` Al Viro
1 sibling, 0 replies; 6+ messages in thread
From: Dawid Osuchowski @ 2024-04-25 10:13 UTC (permalink / raw)
To: Christian Brauner; +Cc: linux-fsdevel, viro, jack
On 4/25/24 11:57, Christian Brauner wrote:
> On Thu, Apr 25, 2024 at 01:38:59AM +0200, Dawid Osuchowski wrote:
>> Creates an anon_inode_getfile_fmode() function that works similarly to
>> anon_inode_getfile() with the addition of being able to set the fmode
>> member.
>
> And for what use-case exactly?
There was a TODO in the vfio driver [1] to create an interface here that
would also allow to set fmode, hence this change.
-- Dawid
[1] https://lore.kernel.org/kvm/20240424234147.7840-1-linux@osuchow.ski/T/#u
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] fs: Create anon_inode_getfile_fmode()
2024-04-25 9:57 ` Christian Brauner
2024-04-25 10:13 ` Dawid Osuchowski
@ 2024-04-25 20:25 ` Al Viro
2024-04-25 21:45 ` Dawid Osuchowski
2024-04-26 8:58 ` Christian Brauner
1 sibling, 2 replies; 6+ messages in thread
From: Al Viro @ 2024-04-25 20:25 UTC (permalink / raw)
To: Christian Brauner; +Cc: Dawid Osuchowski, linux-fsdevel, jack
On Thu, Apr 25, 2024 at 11:57:12AM +0200, Christian Brauner wrote:
> On Thu, Apr 25, 2024 at 01:38:59AM +0200, Dawid Osuchowski wrote:
> > Creates an anon_inode_getfile_fmode() function that works similarly to
> > anon_inode_getfile() with the addition of being able to set the fmode
> > member.
>
> And for what use-case exactly?
There are several places where we might want that -
arch/powerpc/platforms/pseries/papr-vpd.c:488: file = anon_inode_getfile("[papr-vpd]", &papr_vpd_handle_ops,
fs/cachefiles/ondemand.c:233: file = anon_inode_getfile("[cachefiles]", &cachefiles_ondemand_fd_fops,
fs/eventfd.c:412: file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx, flags);
in addition to vfio example Dawid mentions, as well as a couple of
borderline cases in
virt/kvm/kvm_main.c:4404: file = anon_inode_getfile(name, &kvm_vcpu_stats_fops, vcpu, O_RDONLY);
virt/kvm/kvm_main.c:5092: file = anon_inode_getfile("kvm-vm-stats",
So something of that sort is probably a good idea. Said that,
what the hell is __anon_inode_getfile_fmode() for? It's identical
to exported variant, AFAICS. And then there's this:
if (IS_ERR(file))
goto err;
file->f_mode |= f_mode;
return file;
err:
return file;
a really odd way to spell
if (!IS_ERR(file))
file->f_mode |= f_mode;
return file;
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] fs: Create anon_inode_getfile_fmode()
2024-04-25 20:25 ` Al Viro
@ 2024-04-25 21:45 ` Dawid Osuchowski
2024-04-26 8:58 ` Christian Brauner
1 sibling, 0 replies; 6+ messages in thread
From: Dawid Osuchowski @ 2024-04-25 21:45 UTC (permalink / raw)
To: Al Viro, Christian Brauner; +Cc: linux-fsdevel, jack
On 4/25/24 22:25, Al Viro wrote:
> On Thu, Apr 25, 2024 at 11:57:12AM +0200, Christian Brauner wrote:
>> On Thu, Apr 25, 2024 at 01:38:59AM +0200, Dawid Osuchowski wrote:
>>> Creates an anon_inode_getfile_fmode() function that works similarly to
>>> anon_inode_getfile() with the addition of being able to set the fmode
>>> member.
>>
>> And for what use-case exactly?
>
> There are several places where we might want that -
> arch/powerpc/platforms/pseries/papr-vpd.c:488: file = anon_inode_getfile("[papr-vpd]", &papr_vpd_handle_ops,
> fs/cachefiles/ondemand.c:233: file = anon_inode_getfile("[cachefiles]", &cachefiles_ondemand_fd_fops,
> fs/eventfd.c:412: file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx, flags);
> in addition to vfio example Dawid mentions, as well as a couple of
> borderline cases in
> virt/kvm/kvm_main.c:4404: file = anon_inode_getfile(name, &kvm_vcpu_stats_fops, vcpu, O_RDONLY);
> virt/kvm/kvm_main.c:5092: file = anon_inode_getfile("kvm-vm-stats",
>
> So something of that sort is probably a good idea. Said that,
> what the hell is __anon_inode_getfile_fmode() for? It's identical
> to exported variant, AFAICS.
Thank you for the feedback. I tried emulating what I saw in the other
functions (which was clearly wrong). Will address this is in next revision.
And then there's this:
>
> if (IS_ERR(file))
> goto err;
>
> file->f_mode |= f_mode;
>
> return file;
>
> err:
> return file;
>
> a really odd way to spell
>
> if (!IS_ERR(file))
> file->f_mode |= f_mode;
> return file;
Same for this, will rewrite it based on your suggestion.
-- Dawid
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] fs: Create anon_inode_getfile_fmode()
2024-04-25 20:25 ` Al Viro
2024-04-25 21:45 ` Dawid Osuchowski
@ 2024-04-26 8:58 ` Christian Brauner
1 sibling, 0 replies; 6+ messages in thread
From: Christian Brauner @ 2024-04-26 8:58 UTC (permalink / raw)
To: Al Viro; +Cc: Dawid Osuchowski, linux-fsdevel, jack
On Thu, Apr 25, 2024 at 09:25:50PM +0100, Al Viro wrote:
> On Thu, Apr 25, 2024 at 11:57:12AM +0200, Christian Brauner wrote:
> > On Thu, Apr 25, 2024 at 01:38:59AM +0200, Dawid Osuchowski wrote:
> > > Creates an anon_inode_getfile_fmode() function that works similarly to
> > > anon_inode_getfile() with the addition of being able to set the fmode
> > > member.
> >
> > And for what use-case exactly?
>
> There are several places where we might want that -
> arch/powerpc/platforms/pseries/papr-vpd.c:488: file = anon_inode_getfile("[papr-vpd]", &papr_vpd_handle_ops,
> fs/cachefiles/ondemand.c:233: file = anon_inode_getfile("[cachefiles]", &cachefiles_ondemand_fd_fops,
> fs/eventfd.c:412: file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx, flags);
> in addition to vfio example Dawid mentions, as well as a couple of
> borderline cases in
> virt/kvm/kvm_main.c:4404: file = anon_inode_getfile(name, &kvm_vcpu_stats_fops, vcpu, O_RDONLY);
> virt/kvm/kvm_main.c:5092: file = anon_inode_getfile("kvm-vm-stats",
>
> So something of that sort is probably a good idea. Said that,
Ok. It wouldn't be the worst if @Dawid would also sent a follow-patch
converting the obvious cases over to the new helper then.
> what the hell is __anon_inode_getfile_fmode() for? It's identical
Unrelated to this patch but the other really unpleasant part is that
"make_secure" boolean argument to __anon_inode_getfile() to indicate
allocation of a new inode. That "context_inode" argument is also really
unused for the normal case where the same anon_inode_inode is reused...
IMHO, that should just be split apart. A little more code but it would
make things easier to understand imho...
> to exported variant, AFAICS. And then there's this:
>
> if (IS_ERR(file))
> goto err;
>
> file->f_mode |= f_mode;
>
> return file;
>
> err:
> return file;
>
> a really odd way to spell
>
> if (!IS_ERR(file))
> file->f_mode |= f_mode;
> return file;
Yeah.
^ permalink raw reply [flat|nested] 6+ messages in thread
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2024-04-24 23:38 [PATCH] fs: Create anon_inode_getfile_fmode() Dawid Osuchowski
2024-04-25 9:57 ` Christian Brauner
2024-04-25 10:13 ` Dawid Osuchowski
2024-04-25 20:25 ` Al Viro
2024-04-25 21:45 ` Dawid Osuchowski
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