From: "J. Bruce Fields" <bfields@xxxxxxxxxx>
inode_query_iversion() can modify i_version. Depending on the exported
filesystem, that may not be safe. For example, if you're re-exporting
NFS, NFS stores the server's change attribute in i_version and does not
expect it to be modified locally. This has been observed causing
unnecssary cache invalidations.
The way a filesystem indicates that it's OK to call
inode_query_iverson() is by setting SB_I_VERSION.
(This may look like a no-op--in the encode_change() case it's just
rearranging some code--but note nfsd4_change_attribute() is also called
from fill_pre_wcc() and fill_post_wcc().)
(Note we could also pull the NFSEXP_V4ROOT case into
nfsd4_change_attribute as well. That would actually be a no-op, since
pre/post attrs are only used for metadata-modifying operations, and
V4ROOT exports are read-only. But we might make the change in the
future just for simplicity.)
Reported-by: Daire Byrne <daire@xxxxxxxx>
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
---
fs/nfsd/nfs4xdr.c | 6 +-----
fs/nfsd/nfsfh.h | 14 ++++++++++----
2 files changed, 11 insertions(+), 9 deletions(-)
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 833a2c64dfe8..56fd5f6d5c44 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -2298,12 +2298,8 @@ static __be32 *encode_change(__be32 *p, struct kstat *stat, struct inode *inode,
if (exp->ex_flags & NFSEXP_V4ROOT) {
*p++ = cpu_to_be32(convert_to_wallclock(exp->cd->flush_time));
*p++ = 0;
- } else if (IS_I_VERSION(inode)) {
+ } else
p = xdr_encode_hyper(p, nfsd4_change_attribute(stat, inode));
- } else {
- *p++ = cpu_to_be32(stat->ctime.tv_sec);
- *p++ = cpu_to_be32(stat->ctime.tv_nsec);
- }
return p;
}
diff --git a/fs/nfsd/nfsfh.h b/fs/nfsd/nfsfh.h
index 56cfbc361561..3faf5974fa4e 100644
--- a/fs/nfsd/nfsfh.h
+++ b/fs/nfsd/nfsfh.h
@@ -261,10 +261,16 @@ static inline u64 nfsd4_change_attribute(struct kstat *stat,
{
u64 chattr;
- chattr = stat->ctime.tv_sec;
- chattr <<= 30;
- chattr += stat->ctime.tv_nsec;
- chattr += inode_query_iversion(inode);
+ if (IS_I_VERSION(inode)) {
+ chattr = stat->ctime.tv_sec;
+ chattr <<= 30;
+ chattr += stat->ctime.tv_nsec;
+ chattr += inode_query_iversion(inode);
+ } else {
+ chattr = cpu_to_be32(stat->ctime.tv_sec);
+ chattr <<= 32;
+ chattr += cpu_to_be32(stat->ctime.tv_nsec);
+ }
return chattr;
}
--
2.28.0
--
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