Re: [PATCH] efivarfs: expose used and total size
From: Anisse Astier
Date: Mon May 15 2023 - 10:08:44 EST
Hi Christian,
On Mon, May 15, 2023 at 10:59:49AM +0200, Christian Brauner wrote:
> On Wed, May 10, 2023 at 05:13:36PM +0200, Ard Biesheuvel wrote:
> > On Wed, 26 Apr 2023 at 21:59, Anisse Astier <anisse@xxxxxxxxx> wrote:
> > >
> > > From: Anisse Astier <an.astier@xxxxxxxxxx>
> > >
> > > When writing variables, one might get errors with no other message on
> > > why it fails.
> > >
> > > Being able to see how much is used by EFI variables helps analyzing such
> > > issues.
> > >
> > > Since this is not a conventionnal filesystem, block size is
> > > intentionnally set to 1 instead of PAGE_SIZE.
> > >
> > > x86 quirks of reserved size are taken into account and available and
> > > free size can be different, further helping debugging space issues.
> > >
> >
> > I have no objections to this, but I'm not much of a user space/ VFS
> > person, so adding some other folks that can chime in if they want.
> >
> > The point of this patch is that user space can query this information
> > using statvfs(), right?
>
> Seems ok to me.
>
> >
> >
> >
> > > Signed-off-by: Anisse Astier <an.astier@xxxxxxxxxx>
> > > ---
> > > Notes:
> > > Patch isn't split per subsystem intentionally, for better understanding
> > > of intent; split could be trivial in a later version.
> > >
> > > I'm not sure whether statfs(2) should return an error if the efi request
> > > fails; I think it could be ignored with maybe a WARN_ONCE; which would
> > > be close to the current behaviour.
>
> Not sure. If you're not returning an error you would have to report made
> up/magic values that could end up confusing userspace. So better to be
> honest and report an error.
Ack.
>
> > >
> > > Regards,
> > >
> > > Anisse
> > >
> > > ---
> > > arch/x86/platform/efi/quirks.c | 8 ++++++++
> > > drivers/firmware/efi/efi.c | 1 +
> > > drivers/firmware/efi/vars.c | 12 ++++++++++++
> > > fs/efivarfs/super.c | 26 +++++++++++++++++++++++++-
> > > include/linux/efi.h | 10 ++++++++++
> > > 5 files changed, 56 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
> > > index b0b848d6933a..587fa51230e2 100644
> > > --- a/arch/x86/platform/efi/quirks.c
> > > +++ b/arch/x86/platform/efi/quirks.c
> > > @@ -114,6 +114,14 @@ void efi_delete_dummy_variable(void)
> > > EFI_VARIABLE_RUNTIME_ACCESS, 0, NULL);
> > > }
> > >
> > > +u64 efi_reserved_space(void)
> > > +{
> > > + if (efi_no_storage_paranoia)
> > > + return 0;
> > > + return EFI_MIN_RESERVE;
> > > +}
> > > +EXPORT_SYMBOL_GPL(efi_reserved_space);
> > > +
> > > /*
> > > * In the nonblocking case we do not attempt to perform garbage
> > > * collection if we do not have enough free space. Rather, we do the
> > > diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> > > index abeff7dc0b58..d0dfa007bffc 100644
> > > --- a/drivers/firmware/efi/efi.c
> > > +++ b/drivers/firmware/efi/efi.c
> > > @@ -211,6 +211,7 @@ static int generic_ops_register(void)
> > > generic_ops.get_variable = efi.get_variable;
> > > generic_ops.get_next_variable = efi.get_next_variable;
> > > generic_ops.query_variable_store = efi_query_variable_store;
> > > + generic_ops.query_variable_info = efi.query_variable_info;
> > >
> > > if (efi_rt_services_supported(EFI_RT_SUPPORTED_SET_VARIABLE)) {
> > > generic_ops.set_variable = efi.set_variable;
> > > diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
> > > index bd75b87f5fc1..c5382d5c3073 100644
> > > --- a/drivers/firmware/efi/vars.c
> > > +++ b/drivers/firmware/efi/vars.c
> > > @@ -245,3 +245,15 @@ efi_status_t efivar_set_variable(efi_char16_t *name, efi_guid_t *vendor,
> > > return status;
> > > }
> > > EXPORT_SYMBOL_NS_GPL(efivar_set_variable, EFIVAR);
> > > +
> > > +efi_status_t efivar_query_variable_info(u32 attr,
> > > + u64 *storage_space,
> > > + u64 *remaining_space,
> > > + u64 *max_variable_size)
> > > +{
> > > + if (!__efivars->ops->query_variable_info)
> > > + return EFI_UNSUPPORTED;
> > > + return __efivars->ops->query_variable_info(attr, storage_space,
> > > + remaining_space, max_variable_size);
> > > +}
> > > +EXPORT_SYMBOL_NS_GPL(efivar_query_variable_info, EFIVAR);
> > > diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c
> > > index 482d612b716b..064bfc0243c9 100644
> > > --- a/fs/efivarfs/super.c
> > > +++ b/fs/efivarfs/super.c
> > > @@ -13,6 +13,7 @@
> > > #include <linux/ucs2_string.h>
> > > #include <linux/slab.h>
> > > #include <linux/magic.h>
> > > +#include <linux/statfs.h>
> > >
> > > #include "internal.h"
> > >
> > > @@ -23,8 +24,31 @@ static void efivarfs_evict_inode(struct inode *inode)
> > > clear_inode(inode);
> > > }
> > >
> > > +static int efivarfs_statfs(struct dentry *dentry, struct kstatfs *buf)
> > > +{
> > > + u64 storage_space, remaining_space, max_variable_size;
> > > + efi_status_t status;
> > > + const u32 attr = (EFI_VARIABLE_NON_VOLATILE | EFI_VARIABLE_BOOTSERVICE_ACCESS |
> > > + EFI_VARIABLE_RUNTIME_ACCESS);
> > > +
> > > + buf->f_type = dentry->d_sb->s_magic;
> > > + buf->f_bsize = 1;
> > > + buf->f_namelen = NAME_MAX;
> > > +
> > > + status = efivar_query_variable_info(attr, &storage_space, &remaining_space,
> > > + &max_variable_size);
> > > + if (status != EFI_SUCCESS)
> > > + return efi_status_to_err(status);
> > > + buf->f_blocks = storage_space;
>
> I have no idea about efivarfs specifically but I would add comments
> why f_bsize is set to what it is and clarify the relationship between
> f_bsize and f_blocks. Even if just for the sake of userspace to be able
> to interpret this.
Ack.
Thanks for taking the time to review this patch, I'll send a new version
soon.
Regards,
Anisse