From: "J. Bruce Fields" <[email protected]> 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 <[email protected]> Signed-off-by: J. Bruce Fields <[email protected]> --- 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 -- Linux-cachefs mailing list [email protected] https://www.redhat.com/mailman/listinfo/linux-cachefs
