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Message-ID: <c10e4aa381aea86bb51b005887533e28f9c7302b.camel@redhat.com> Date: Fri, 05 Aug 2022 18:06:36 -0400 From: Jeff Layton <jlayton@...hat.com> To: Dave Chinner <david@...morbit.com> Cc: linux-fsdevel@...r.kernel.org, dhowells@...hat.com, lczerner@...hat.com, bxue@...hat.com, ceph-devel@...r.kernel.org, linux-nfs@...r.kernel.org, linux-afs@...ts.infradead.org, linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org, linux-btrfs@...r.kernel.org Subject: Re: [RFC PATCH 1/4] vfs: report change attribute in statx for IS_I_VERSION inodes On Sat, 2022-08-06 at 08:01 +1000, Dave Chinner wrote: > On Fri, Aug 05, 2022 at 02:35:40PM -0400, Jeff Layton wrote: > > From: Jeff Layton <jlayton@...hat.com> > > > > Claim one of the spare fields in struct statx to hold a 64-bit change > > attribute. When statx requests this attribute, do an > > inode_query_iversion and fill the result in the field. > > > > Also update the test-statx.c program to fetch the change attribute as > > well. > > > > Signed-off-by: Jeff Layton <jlayton@...nel.org> > > --- > > fs/stat.c | 7 +++++++ > > include/linux/stat.h | 1 + > > include/uapi/linux/stat.h | 3 ++- > > samples/vfs/test-statx.c | 4 +++- > > 4 files changed, 13 insertions(+), 2 deletions(-) > > > > diff --git a/fs/stat.c b/fs/stat.c > > index 9ced8860e0f3..976e0a59ab23 100644 > > --- a/fs/stat.c > > +++ b/fs/stat.c > > @@ -17,6 +17,7 @@ > > #include <linux/syscalls.h> > > #include <linux/pagemap.h> > > #include <linux/compat.h> > > +#include <linux/iversion.h> > > > > #include <linux/uaccess.h> > > #include <asm/unistd.h> > > @@ -118,6 +119,11 @@ int vfs_getattr_nosec(const struct path *path, struct kstat *stat, > > stat->attributes_mask |= (STATX_ATTR_AUTOMOUNT | > > STATX_ATTR_DAX); > > > > + if ((request_mask & STATX_CHGATTR) && IS_I_VERSION(inode)) { > > + stat->result_mask |= STATX_CHGATTR; > > + stat->chgattr = inode_query_iversion(inode); > > + } > > If you're going to add generic support for it, shouldn't there be a > generic test in fstests that ensures that filesystems that advertise > STATX_CHGATTR support actually behave correctly? Including across > mounts, and most importantly, that it is made properly stable by > fsync? > > i.e. what good is this if different filesystems have random quirks > that mean it can't be relied on by userspace to tell it changes have > occurred? Absolutely. Being able to better test the i_version field for consistent behavior is a primary goal. I haven't yet written any yet, but we'd definitely want something in xfstests if we decide this is worthwhile. -- Jeff Layton <jlayton@...hat.com>
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