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Subject[34-longterm 163/209] nfsd: Fix possible BUG_ON firing in set_change_info
Date
From: Neil Brown <neilb@suse.de>

=====================================================================
| This is a commit scheduled for the next v2.6.34 longterm release. |
| If you see a problem with using this for longterm, please comment.|
=====================================================================

commit c1ac3ffcd0bc7e9617f62be8c7043d53ab84deac upstream.

If vfs_getattr in fill_post_wcc returns an error, we don't
set fh_post_change.
For NFSv4, this can result in set_change_info triggering a BUG_ON.
i.e. fh_post_saved being zero isn't really a bug.

So:
- instead of BUGging when fh_post_saved is zero, just clear ->atomic.
- if vfs_getattr fails in fill_post_wcc, take a copy of i_ctime anyway.
This will be used i seg_change_info, but not overly trusted.
- While we are there, remove the pointless 'if' statements in set_change_info.
There is no harm setting all the values.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
fs/nfsd/nfs3xdr.c | 6 ++++--
fs/nfsd/xdr4.h | 21 ++++++++++-----------
2 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index 2a533a0..7e84a85 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -260,9 +260,11 @@ void fill_post_wcc(struct svc_fh *fhp)
err = vfs_getattr(fhp->fh_export->ex_path.mnt, fhp->fh_dentry,
&fhp->fh_post_attr);
fhp->fh_post_change = fhp->fh_dentry->d_inode->i_version;
- if (err)
+ if (err) {
fhp->fh_post_saved = 0;
- else
+ /* Grab the ctime anyway - set_change_info might use it */
+ fhp->fh_post_attr.ctime = fhp->fh_dentry->d_inode->i_ctime;
+ } else
fhp->fh_post_saved = 1;
}

diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
index efa3377..c1aed78 100644
--- a/fs/nfsd/xdr4.h
+++ b/fs/nfsd/xdr4.h
@@ -479,18 +479,17 @@ static inline bool nfsd4_not_cached(struct nfsd4_compoundres *resp)
static inline void
set_change_info(struct nfsd4_change_info *cinfo, struct svc_fh *fhp)
{
- BUG_ON(!fhp->fh_pre_saved || !fhp->fh_post_saved);
- cinfo->atomic = 1;
+ BUG_ON(!fhp->fh_pre_saved);
+ cinfo->atomic = fhp->fh_post_saved;
cinfo->change_supported = IS_I_VERSION(fhp->fh_dentry->d_inode);
- if (cinfo->change_supported) {
- cinfo->before_change = fhp->fh_pre_change;
- cinfo->after_change = fhp->fh_post_change;
- } else {
- cinfo->before_ctime_sec = fhp->fh_pre_ctime.tv_sec;
- cinfo->before_ctime_nsec = fhp->fh_pre_ctime.tv_nsec;
- cinfo->after_ctime_sec = fhp->fh_post_attr.ctime.tv_sec;
- cinfo->after_ctime_nsec = fhp->fh_post_attr.ctime.tv_nsec;
- }
+
+ cinfo->before_change = fhp->fh_pre_change;
+ cinfo->after_change = fhp->fh_post_change;
+ cinfo->before_ctime_sec = fhp->fh_pre_ctime.tv_sec;
+ cinfo->before_ctime_nsec = fhp->fh_pre_ctime.tv_nsec;
+ cinfo->after_ctime_sec = fhp->fh_post_attr.ctime.tv_sec;
+ cinfo->after_ctime_nsec = fhp->fh_post_attr.ctime.tv_nsec;
+
}

int nfs4svc_encode_voidres(struct svc_rqst *, __be32 *, void *);
--
1.7.4.4


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