From: Jeff Layton <jeff.layton@xxxxxxxxxxxxxxx>
It's not uncommon for some workloads to do a bunch of I/O to a file and
delete it just afterward. If knfsd has a cached open file however, then
the file may still be open when the dentry is unlinked. If the
underlying filesystem is nfs, then that could trigger it to do a
sillyrename.
On a REMOVE or RENAME scan the nfsd_file cache for open files that
correspond to the inode, and proactively unhash and put their
references. This should prevent any delete-on-last-close activity from
occurring, solely due to knfsd's open file cache.
This must be done synchronously though so we use the variants that call
flush_delayed_fput. There are deadlock possibilities if you call
flush_delayed_fput while holding locks, however. In the case of
nfsd_rename, we don't even do the lookups of the dentries to be renamed
until we've locked for rename.
Once we've figured out what the target dentry is for a rename, check to
see whether there are cached open files associated with it. If there
are, then unwind all of the locking, close them all, and then reattempt
the rename.
Signed-off-by: Jeff Layton <jeff.layton@xxxxxxxxxxxxxxx>
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
---
fs/nfsd/vfs.c | 62 +++++++++++++++++++++++++++++++++++++++++++--------
1 file changed, 53 insertions(+), 9 deletions(-)
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 58b6d8df95d4..f5cf64a40112 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1590,6 +1590,26 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
goto out_unlock;
}
+static void
+nfsd_close_cached_files(struct dentry *dentry)
+{
+ struct inode *inode = d_inode(dentry);
+
+ if (inode && S_ISREG(inode->i_mode))
+ nfsd_file_close_inode_sync(inode);
+}
+
+static bool
+nfsd_has_cached_files(struct dentry *dentry)
+{
+ bool ret = false;
+ struct inode *inode = d_inode(dentry);
+
+ if (inode && S_ISREG(inode->i_mode))
+ ret = nfsd_file_is_cached(inode);
+ return ret;
+}
+
/*
* Rename a file
* N.B. After this call _both_ ffhp and tfhp need an fh_put
@@ -1602,6 +1622,7 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
struct inode *fdir, *tdir;
__be32 err;
int host_err;
+ bool has_cached = false;
err = fh_verify(rqstp, ffhp, S_IFDIR, NFSD_MAY_REMOVE);
if (err)
@@ -1620,6 +1641,7 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
if (!flen || isdotent(fname, flen) || !tlen || isdotent(tname, tlen))
goto out;
+retry:
host_err = fh_want_write(ffhp);
if (host_err) {
err = nfserrno(host_err);
@@ -1659,11 +1681,16 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
if (ffhp->fh_export->ex_path.dentry != tfhp->fh_export->ex_path.dentry)
goto out_dput_new;
- host_err = vfs_rename(fdir, odentry, tdir, ndentry, NULL, 0);
- if (!host_err) {
- host_err = commit_metadata(tfhp);
- if (!host_err)
- host_err = commit_metadata(ffhp);
+ if (nfsd_has_cached_files(ndentry)) {
+ has_cached = true;
+ goto out_dput_old;
+ } else {
+ host_err = vfs_rename(fdir, odentry, tdir, ndentry, NULL, 0);
+ if (!host_err) {
+ host_err = commit_metadata(tfhp);
+ if (!host_err)
+ host_err = commit_metadata(ffhp);
+ }
}
out_dput_new:
dput(ndentry);
@@ -1676,12 +1703,26 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
* as that would do the wrong thing if the two directories
* were the same, so again we do it by hand.
*/
- fill_post_wcc(ffhp);
- fill_post_wcc(tfhp);
+ if (!has_cached) {
+ fill_post_wcc(ffhp);
+ fill_post_wcc(tfhp);
+ }
unlock_rename(tdentry, fdentry);
ffhp->fh_locked = tfhp->fh_locked = false;
fh_drop_write(ffhp);
+ /*
+ * If the target dentry has cached open files, then we need to try to
+ * close them prior to doing the rename. Flushing delayed fput
+ * shouldn't be done with locks held however, so we delay it until this
+ * point and then reattempt the whole shebang.
+ */
+ if (has_cached) {
+ has_cached = false;
+ nfsd_close_cached_files(ndentry);
+ dput(ndentry);
+ goto retry;
+ }
out:
return err;
}
@@ -1728,10 +1769,13 @@ nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
if (!type)
type = d_inode(rdentry)->i_mode & S_IFMT;
- if (type != S_IFDIR)
+ if (type != S_IFDIR) {
+ nfsd_close_cached_files(rdentry);
host_err = vfs_unlink(dirp, rdentry, NULL);
- else
+ } else {
host_err = vfs_rmdir(dirp, rdentry);
+ }
+
if (!host_err)
host_err = commit_metadata(fhp);
dput(rdentry);
--
2.21.0
