On Mon, Oct 12, 2015 at 6:05 AM, Dave Chinner <david@xxxxxxxxxxxxx> wrote: > On Mon, Oct 12, 2015 at 03:51:15AM +0200, Andreas Grünbacher wrote: >> 2015-10-12 2:10 GMT+02:00 Dave Chinner <david@xxxxxxxxxxxxx>: >> > On Mon, Oct 12, 2015 at 12:58:35AM +0200, Andreas Gruenbacher wrote: >> >> diff --git a/fs/xfs/Kconfig b/fs/xfs/Kconfig >> >> index 5d47b4d..05dd312 100644 >> >> --- a/fs/xfs/Kconfig >> >> +++ b/fs/xfs/Kconfig >> >> @@ -52,6 +52,17 @@ config XFS_POSIX_ACL >> >> >> >> If you don't know what Access Control Lists are, say N. >> >> >> >> +config XFS_RICHACL >> >> + bool "XFS Rich Access Control Lists (EXPERIMENTAL)" >> >> + depends on XFS_FS >> >> + select FS_RICHACL >> >> + help >> >> + Richacls are an implementation of NFSv4 ACLs, extended by file masks >> >> + to cleanly integrate into the POSIX file permission model. To learn >> >> + more about them, see http://www.bestbits.at/richacl/. >> >> + >> >> + If you don't know what Richacls are, say N. >> >> + >> > >> > So now we have multiple compile time ACL configs that we have to >> > test. Personally, I see no reason for making either posix or rich >> > acls compile time dependent. How about we just change CONFIG_FS_XFS >> > to have "select FS_POSIX_ACL" and "select FS_RICHACL" >> > unconditionally, and then we can get rid of all the conditional >> > code? >> >> I'm sure neither kind of ACLs makes sense on many tiny systems, it >> should be possible to disable them. XFS may not make sense on those >> kinds of systems either, that is not my call to make though. > > Well, the smallest systems that use XFS are typically 1-2 disk NAS > boxes, and I can see them wanting richacls. As it is, the xfs kernel > module is almost 1MB of object code, so it you have a small embedded > box you don't want XFS. Almost all distros turn on ACL support I'm > not sure that it makes sense to have these config options in XFS > anymore.... You have me convinced about removing CONFIG_XFS_RICHACL. >> >> diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h >> >> index 9590a06..8c6da45 100644 >> >> --- a/fs/xfs/libxfs/xfs_format.h >> >> +++ b/fs/xfs/libxfs/xfs_format.h >> >> @@ -461,10 +461,18 @@ xfs_sb_has_ro_compat_feature( >> >> #define XFS_SB_FEAT_INCOMPAT_FTYPE (1 << 0) /* filetype in dirent */ >> >> #define XFS_SB_FEAT_INCOMPAT_SPINODES (1 << 1) /* sparse inode chunks */ >> >> #define XFS_SB_FEAT_INCOMPAT_META_UUID (1 << 2) /* metadata UUID */ >> >> + >> >> +#ifdef CONFIG_XFS_RICHACL >> >> +#define XFS_SB_FEAT_INCOMPAT_RICHACL (1 << 3) /* richacls */ >> >> +#else >> >> +#define XFS_SB_FEAT_INCOMPAT_RICHACL 0 >> >> +#endif >> >> + >> > >> > Regardless of whether we build in richacl support, this is wrong. >> > Feature bits are on-disk format definitions, so it will always have >> > this value whether or not the kernel supports the feature. >> >> This is so that xfs_mount_validate_sb() will complain when mounting a >> richacl filesystem on a kernel which doesn't have richacl suport >> compiled in. The same effect can be had with extra code there of >> course. > > If the kernel doesn't know about a feature, then it will report > "unknown feature". However, as of this patch set, the kernel will > know about the richacl feature, and so the correct error message > is to say "Rich ACLs not supported by this kernel". > > Also, from a disk format perspective, this is a this is a read-only > compat feature, as kernels that don't have richacl support are still > able to mount and walk the filesystem without errors occurring. It's > only when allowing modifications are made that problems will arise, > so why did you make it an incompat feature? As a read-only compat flag, kernels that cannot enforce richacls would still be able to mount richacl file systems read-only. That's a problem when acls are used to forbid read/execute access. >> >> +int >> >> +xfs_set_richacl(struct inode *inode, struct richacl *acl) >> >> +{ >> >> + struct xfs_inode *ip = XFS_I(inode); >> >> + umode_t mode = inode->i_mode; >> >> + int error; >> >> + >> >> + if (acl) { >> >> + /* Don't allow acls with unmapped identifiers. */ >> >> + if (richacl_has_unmapped_identifiers(acl)) >> >> + return -EINVAL; >> >> + >> >> + if (richacl_equiv_mode(acl, &mode) == 0) { >> >> + xfs_set_mode(inode, mode); >> >> + acl = NULL; >> >> + } >> > >> > Comment needed here - why does this now seem to accidentally fall >> > through to removing the ACL? >> >> Setting an ACL that is equivalent to a file mode is the same as >> removing any existing ACLs and doing a chmod to that equivalent file >> mode. It's the sams as with POSIX ACLs, and the code is the same as >> well. I'll add a comment though. >> >> > Also, why is this in the XFS specific >> > code when it's generic richacl functionality that is being checked? >> >> This turns into two non-atomic operations if we move it into generic code. > > I don't follow you - this isn't an atomic operation to begin with... Right, I shouldn't have used the term atomic. It's one inode operation under i_mutex, and the filesystem can pack it into one transaction. Thanks, Andreas -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
