[PATCH v2 0/6] Patches to support NFS re-exporting

[PATCH v2 0/6] Patches to support NFS re-exporting

[trondmy]

From: Trond Myklebust <trond.myklebust@hammerspace.com>

These patches fix a number of issues that Hammerspace has hit when doing
re-exporting of NFS.

- v2: Rebased on top of cel-next.

Jeff Layton (3):
  nfsd: add a new EXPORT_OP_NOWCC flag to struct export_operations
  nfsd: allow filesystems to opt out of subtree checking
  nfsd: close cached files prior to a REMOVE or RENAME that would
    replace target

Trond Myklebust (3):
  exportfs: Add a function to return the raw output from fh_to_dentry()
  nfsd: Fix up nfsd to ensure that timeout errors don't result in ESTALE
  nfsd: Set PF_LOCAL_THROTTLE on local filesystems only

 Documentation/filesystems/nfs/exporting.rst | 52 +++++++++++++++++++++
 fs/exportfs/expfs.c                         | 32 +++++++++----
 fs/nfs/export.c                             |  2 +
 fs/nfsd/export.c                            |  6 +++
 fs/nfsd/nfs3xdr.c                           |  7 ++-
 fs/nfsd/nfsfh.c                             | 30 ++++++++++--
 fs/nfsd/nfsfh.h                             |  2 +-
 fs/nfsd/vfs.c                               | 29 ++++++++----
 include/linux/exportfs.h                    | 10 ++++
 9 files changed, 146 insertions(+), 24 deletions(-)

-- 
2.28.0

[PATCH v2 1/6] nfsd: add a new EXPORT_OP_NOWCC flag to struct export_operations

[trondmy]

From: Jeff Layton <jeff.layton@primarydata.com>

With NFSv3 nfsd will always attempt to send along WCC data to the
client. This generally involves saving off the in-core inode information
prior to doing the operation on the given filehandle, and then issuing a
vfs_getattr to it after the op.

Some filesystems (particularly clustered or networked ones) have an
expensive ->getattr inode operation. Atomicitiy is also often difficult
or impossible to guarantee on such filesystems. For those, we're best
off not trying to provide WCC information to the client at all, and to
simply allow it to poll for that information as needed with a GETATTR
RPC.

This patch adds a new flags field to struct export_operations, and
defines a new EXPORT_OP_NOWCC flag that filesystems can use to indicate
that nfsd should not attempt to provide WCC info in NFSv3 replies. It
also adds a blurb about the new flags field and flag to the exporting
documentation.

The server will also now skip collecting this information for NFSv2 as
well, since that info is never used there anyway.

Note that this patch does not add this flag to any filesystem
export_operations structures. This was originally developed to allow
reexporting nfs via nfsd. That code is not (and may never be) suitable
for merging into mainline.

Other filesystems may want to consider enabling this flag too. It's hard
to tell however which ones have export operations to enable export via
knfsd and which ones mostly rely on them for open-by-filehandle support,
so I'm leaving that up to the individual maintainers to decide. I am
cc'ing the relevant lists for those filesystems that I think may want to
consider adding this though.

Cc: HPDD-discuss@lists.01.org
Cc: ceph-devel@vger.kernel.org
Cc: cluster-devel@redhat.com
Cc: fuse-devel@lists.sourceforge.net
Cc: ocfs2-devel@oss.oracle.com
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: Lance Shelton <lance.shelton@hammerspace.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 Documentation/filesystems/nfs/exporting.rst | 27 +++++++++++++++++++++
 fs/nfs/export.c                             |  1 +
 fs/nfsd/nfs3xdr.c                           |  7 ++++--
 fs/nfsd/nfsfh.c                             | 14 +++++++++++
 fs/nfsd/nfsfh.h                             |  2 +-
 include/linux/exportfs.h                    |  2 ++
 6 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/Documentation/filesystems/nfs/exporting.rst b/Documentation/filesystems/nfs/exporting.rst
index 33d588a01ace..cbe542ad5233 100644
--- a/Documentation/filesystems/nfs/exporting.rst
+++ b/Documentation/filesystems/nfs/exporting.rst
@@ -154,6 +154,11 @@ struct which has the following members:
     to find potential names, and matches inode numbers to find the correct
     match.
 
+  flags
+    Some filesystems may need to be handled differently than others. The
+    export_operations struct also includes a flags field that allows the
+    filesystem to communicate such information to nfsd. See the Export
+    Operations Flags section below for more explanation.
 
 A filehandle fragment consists of an array of 1 or more 4byte words,
 together with a one byte "type".
@@ -163,3 +168,25 @@ generated by encode_fh, in which case it will have been padded with
 nuls.  Rather, the encode_fh routine should choose a "type" which
 indicates the decode_fh how much of the filehandle is valid, and how
 it should be interpreted.
+
+Export Operations Flags
+-----------------------
+In addition to the operation vector pointers, struct export_operations also
+contains a "flags" field that allows the filesystem to communicate to nfsd
+that it may want to do things differently when dealing with it. The
+following flags are defined:
+
+  EXPORT_OP_NOWCC - disable NFSv3 WCC attributes on this filesystem
+    RFC 1813 recommends that servers always send weak cache consistency
+    (WCC) data to the client after each operation. The server should
+    atomically collect attributes about the inode, do an operation on it,
+    and then collect the attributes afterward. This allows the client to
+    skip issuing GETATTRs in some situations but means that the server
+    is calling vfs_getattr for almost all RPCs. On some filesystems
+    (particularly those that are clustered or networked) this is expensive
+    and atomicity is difficult to guarantee. This flag indicates to nfsd
+    that it should skip providing WCC attributes to the client in NFSv3
+    replies when doing operations on this filesystem. Consider enabling
+    this on filesystems that have an expensive ->getattr inode operation,
+    or when atomicity between pre and post operation attribute collection
+    is impossible to guarantee.
diff --git a/fs/nfs/export.c b/fs/nfs/export.c
index 3430d6891e89..8f4c528865c5 100644
--- a/fs/nfs/export.c
+++ b/fs/nfs/export.c
@@ -171,4 +171,5 @@ const struct export_operations nfs_export_ops = {
 	.encode_fh = nfs_encode_fh,
 	.fh_to_dentry = nfs_fh_to_dentry,
 	.get_parent = nfs_get_parent,
+	.flags = EXPORT_OP_NOWCC,
 };
diff --git a/fs/nfsd/nfs3xdr.c b/fs/nfsd/nfs3xdr.c
index b0a53c857706..821db21ba072 100644
--- a/fs/nfsd/nfs3xdr.c
+++ b/fs/nfsd/nfs3xdr.c
@@ -206,7 +206,7 @@ static __be32 *
 encode_post_op_attr(struct svc_rqst *rqstp, __be32 *p, struct svc_fh *fhp)
 {
 	struct dentry *dentry = fhp->fh_dentry;
-	if (dentry && d_really_is_positive(dentry)) {
+	if (!fhp->fh_no_wcc && dentry && d_really_is_positive(dentry)) {
 	        __be32 err;
 		struct kstat stat;
 
@@ -262,7 +262,7 @@ void fill_pre_wcc(struct svc_fh *fhp)
 	bool v4 = (fhp->fh_maxsize == NFS4_FHSIZE);
 	__be32 err;
 
-	if (fhp->fh_pre_saved)
+	if (fhp->fh_no_wcc || fhp->fh_pre_saved)
 		return;
 	inode = d_inode(fhp->fh_dentry);
 	err = fh_getattr(fhp, &stat);
@@ -290,6 +290,9 @@ void fill_post_wcc(struct svc_fh *fhp)
 	struct inode *inode = d_inode(fhp->fh_dentry);
 	__be32 err;
 
+	if (fhp->fh_no_wcc)
+		return;
+
 	if (fhp->fh_post_saved)
 		printk("nfsd: inode locked twice during operation.\n");
 
diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
index c81dbbad8792..0c2ee65e46f3 100644
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -291,6 +291,16 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp)
 
 	fhp->fh_dentry = dentry;
 	fhp->fh_export = exp;
+
+	switch (rqstp->rq_vers) {
+	case 3:
+		if (!(dentry->d_sb->s_export_op->flags & EXPORT_OP_NOWCC))
+			break;
+		/* Fallthrough */
+	case 2:
+		fhp->fh_no_wcc = true;
+	}
+
 	return 0;
 out:
 	exp_put(exp);
@@ -559,6 +569,9 @@ fh_compose(struct svc_fh *fhp, struct svc_export *exp, struct dentry *dentry,
 	 */
 	set_version_and_fsid_type(fhp, exp, ref_fh);
 
+	/* If we have a ref_fh, then copy the fh_no_wcc setting from it. */
+	fhp->fh_no_wcc = ref_fh ? ref_fh->fh_no_wcc : false;
+
 	if (ref_fh == fhp)
 		fh_put(ref_fh);
 
@@ -662,6 +675,7 @@ fh_put(struct svc_fh *fhp)
 		exp_put(exp);
 		fhp->fh_export = NULL;
 	}
+	fhp->fh_no_wcc = false;
 	return;
 }
 
diff --git a/fs/nfsd/nfsfh.h b/fs/nfsd/nfsfh.h
index 45bd776290d5..347d10aa6265 100644
--- a/fs/nfsd/nfsfh.h
+++ b/fs/nfsd/nfsfh.h
@@ -35,6 +35,7 @@ typedef struct svc_fh {
 
 	bool			fh_locked;	/* inode locked by us */
 	bool			fh_want_write;	/* remount protection taken */
+	bool			fh_no_wcc;	/* no wcc data needed */
 	int			fh_flags;	/* FH flags */
 #ifdef CONFIG_NFSD_V3
 	bool			fh_post_saved;	/* post-op attrs saved */
@@ -54,7 +55,6 @@ typedef struct svc_fh {
 	struct kstat		fh_post_attr;	/* full attrs after operation */
 	u64			fh_post_change; /* nfsv4 change; see above */
 #endif /* CONFIG_NFSD_V3 */
-
 } svc_fh;
 #define NFSD4_FH_FOREIGN (1<<0)
 #define SET_FH_FLAG(c, f) ((c)->fh_flags |= (f))
diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
index 3ceb72b67a7a..e7de0103a32e 100644
--- a/include/linux/exportfs.h
+++ b/include/linux/exportfs.h
@@ -213,6 +213,8 @@ struct export_operations {
 			  bool write, u32 *device_generation);
 	int (*commit_blocks)(struct inode *inode, struct iomap *iomaps,
 			     int nr_iomaps, struct iattr *iattr);
+#define	EXPORT_OP_NOWCC		(0x1)	/* Don't collect wcc data for NFSv3 replies */
+	unsigned long	flags;
 };
 
 extern int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
-- 
2.28.0

[PATCH v2 2/6] nfsd: allow filesystems to opt out of subtree checking

[trondmy]

From: Jeff Layton <jeff.layton@primarydata.com>

When we start allowing NFS to be reexported, then we have some problems
when it comes to subtree checking. In principle, we could allow it, but
it would mean encoding parent info in the filehandles and there may not
be enough space for that in a NFSv3 filehandle.

To enforce this at export upcall time, we add a new export_ops flag
that declares the filesystem ineligible for subtree checking.

Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: Lance Shelton <lance.shelton@hammerspace.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 Documentation/filesystems/nfs/exporting.rst | 12 ++++++++++++
 fs/nfs/export.c                             |  2 +-
 fs/nfsd/export.c                            |  6 ++++++
 include/linux/exportfs.h                    |  1 +
 4 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/Documentation/filesystems/nfs/exporting.rst b/Documentation/filesystems/nfs/exporting.rst
index cbe542ad5233..960be64446cb 100644
--- a/Documentation/filesystems/nfs/exporting.rst
+++ b/Documentation/filesystems/nfs/exporting.rst
@@ -190,3 +190,15 @@ following flags are defined:
     this on filesystems that have an expensive ->getattr inode operation,
     or when atomicity between pre and post operation attribute collection
     is impossible to guarantee.
+
+  EXPORT_OP_NOSUBTREECHK - disallow subtree checking on this fs
+    Many NFS operations deal with filehandles, which the server must then
+    vet to ensure that they live inside of an exported tree. When the
+    export consists of an entire filesystem, this is trivial. nfsd can just
+    ensure that the filehandle live on the filesystem. When only part of a
+    filesystem is exported however, then nfsd must walk the ancestors of the
+    inode to ensure that it's within an exported subtree. This is an
+    expensive operation and not all filesystems can support it properly.
+    This flag exempts the filesystem from subtree checking and causes
+    exportfs to get back an error if it tries to enable subtree checking
+    on it.
diff --git a/fs/nfs/export.c b/fs/nfs/export.c
index 8f4c528865c5..b9ba306bf912 100644
--- a/fs/nfs/export.c
+++ b/fs/nfs/export.c
@@ -171,5 +171,5 @@ const struct export_operations nfs_export_ops = {
 	.encode_fh = nfs_encode_fh,
 	.fh_to_dentry = nfs_fh_to_dentry,
 	.get_parent = nfs_get_parent,
-	.flags = EXPORT_OP_NOWCC,
+	.flags = EXPORT_OP_NOWCC|EXPORT_OP_NOSUBTREECHK,
 };
diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
index 21e404e7cb68..81e7bb12aca6 100644
--- a/fs/nfsd/export.c
+++ b/fs/nfsd/export.c
@@ -408,6 +408,12 @@ static int check_export(struct inode *inode, int *flags, unsigned char *uuid)
 		return -EINVAL;
 	}
 
+	if (inode->i_sb->s_export_op->flags & EXPORT_OP_NOSUBTREECHK &&
+	    !(*flags & NFSEXP_NOSUBTREECHECK)) {
+		dprintk("%s: %s does not support subtree checking!\n",
+			__func__, inode->i_sb->s_type->name);
+		return -EINVAL;
+	}
 	return 0;
 
 }
diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
index e7de0103a32e..2fcbab0f6b61 100644
--- a/include/linux/exportfs.h
+++ b/include/linux/exportfs.h
@@ -214,6 +214,7 @@ struct export_operations {
 	int (*commit_blocks)(struct inode *inode, struct iomap *iomaps,
 			     int nr_iomaps, struct iattr *iattr);
 #define	EXPORT_OP_NOWCC		(0x1)	/* Don't collect wcc data for NFSv3 replies */
+#define	EXPORT_OP_NOSUBTREECHK	(0x2)	/* Subtree checking is not supported! */
 	unsigned long	flags;
 };
 
-- 
2.28.0

[PATCH v2 3/6] nfsd: close cached files prior to a REMOVE or RENAME that would replace target

[trondmy]

From: Jeff Layton <jeff.layton@primarydata.com>

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.

None of this is really necessary for "typical" filesystems though. It's
mostly of use for NFS, so declare a new export op flag and use that to
determine whether to close the files beforehand.

Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Signed-off-by: Lance Shelton <lance.shelton@hammerspace.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 Documentation/filesystems/nfs/exporting.rst | 13 +++++++++++++
 fs/nfs/export.c                             |  2 +-
 fs/nfsd/vfs.c                               | 16 +++++++++-------
 include/linux/exportfs.h                    |  5 +++--
 4 files changed, 26 insertions(+), 10 deletions(-)

diff --git a/Documentation/filesystems/nfs/exporting.rst b/Documentation/filesystems/nfs/exporting.rst
index 960be64446cb..0e98edd353b5 100644
--- a/Documentation/filesystems/nfs/exporting.rst
+++ b/Documentation/filesystems/nfs/exporting.rst
@@ -202,3 +202,16 @@ following flags are defined:
     This flag exempts the filesystem from subtree checking and causes
     exportfs to get back an error if it tries to enable subtree checking
     on it.
+
+  EXPORT_OP_CLOSE_BEFORE_UNLINK - always close cached files before unlinking
+    On some exportable filesystems (such as NFS) unlinking a file that
+    is still open can cause a fair bit of extra work. For instance,
+    the NFS client will do a "sillyrename" to ensure that the file
+    sticks around while it's still open. When reexporting, that open
+    file is held by nfsd so we usually end up doing a sillyrename, and
+    then immediately deleting the sillyrenamed file just afterward when
+    the link count actually goes to zero. Sometimes this delete can race
+    with other operations (for instance an rmdir of the parent directory).
+    This flag causes nfsd to close any open files for this inode _before_
+    calling into the vfs to do an unlink or a rename that would replace
+    an existing file.
diff --git a/fs/nfs/export.c b/fs/nfs/export.c
index b9ba306bf912..5428713af5fe 100644
--- a/fs/nfs/export.c
+++ b/fs/nfs/export.c
@@ -171,5 +171,5 @@ const struct export_operations nfs_export_ops = {
 	.encode_fh = nfs_encode_fh,
 	.fh_to_dentry = nfs_fh_to_dentry,
 	.get_parent = nfs_get_parent,
-	.flags = EXPORT_OP_NOWCC|EXPORT_OP_NOSUBTREECHK,
+	.flags = EXPORT_OP_NOWCC|EXPORT_OP_NOSUBTREECHK|EXPORT_OP_CLOSE_BEFORE_UNLINK,
 };
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 1ecaceebee13..79cba942087e 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1724,7 +1724,7 @@ 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;
+	bool		close_cached = false;
 
 	err = fh_verify(rqstp, ffhp, S_IFDIR, NFSD_MAY_REMOVE);
 	if (err)
@@ -1783,8 +1783,9 @@ 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;
 
-	if (nfsd_has_cached_files(ndentry)) {
-		has_cached = true;
+	if ((ndentry->d_sb->s_export_op->flags & EXPORT_OP_CLOSE_BEFORE_UNLINK) &&
+	    nfsd_has_cached_files(ndentry)) {
+		close_cached = true;
 		goto out_dput_old;
 	} else {
 		host_err = vfs_rename(fdir, odentry, tdir, ndentry, NULL, 0);
@@ -1805,7 +1806,7 @@ 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.
 	 */
-	if (!has_cached) {
+	if (!close_cached) {
 		fill_post_wcc(ffhp);
 		fill_post_wcc(tfhp);
 	}
@@ -1819,8 +1820,8 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
 	 * 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;
+	if (close_cached) {
+		close_cached = false;
 		nfsd_close_cached_files(ndentry);
 		dput(ndentry);
 		goto retry;
@@ -1872,7 +1873,8 @@ nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
 		type = d_inode(rdentry)->i_mode & S_IFMT;
 
 	if (type != S_IFDIR) {
-		nfsd_close_cached_files(rdentry);
+		if (rdentry->d_sb->s_export_op->flags & EXPORT_OP_CLOSE_BEFORE_UNLINK)
+			nfsd_close_cached_files(rdentry);
 		host_err = vfs_unlink(dirp, rdentry, NULL);
 	} else {
 		host_err = vfs_rmdir(dirp, rdentry);
diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
index 2fcbab0f6b61..d829403ffd3b 100644
--- a/include/linux/exportfs.h
+++ b/include/linux/exportfs.h
@@ -213,8 +213,9 @@ struct export_operations {
 			  bool write, u32 *device_generation);
 	int (*commit_blocks)(struct inode *inode, struct iomap *iomaps,
 			     int nr_iomaps, struct iattr *iattr);
-#define	EXPORT_OP_NOWCC		(0x1)	/* Don't collect wcc data for NFSv3 replies */
-#define	EXPORT_OP_NOSUBTREECHK	(0x2)	/* Subtree checking is not supported! */
+#define	EXPORT_OP_NOWCC			(0x1) /* don't collect v3 wcc data */
+#define	EXPORT_OP_NOSUBTREECHK		(0x2) /* no subtree checking */
+#define	EXPORT_OP_CLOSE_BEFORE_UNLINK	(0x4) /* close files before unlink */
 	unsigned long	flags;
 };
 
-- 
2.28.0

[PATCH v2 4/6] exportfs: Add a function to return the raw output from fh_to_dentry()

[trondmy]

From: Trond Myklebust <trond.myklebust@hammerspace.com>

In order to allow nfsd to accept return values that are not
acceptable to overlayfs and others, add a new function.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/exportfs/expfs.c      | 32 ++++++++++++++++++++++++--------
 include/linux/exportfs.h |  5 +++++
 2 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
index 2dd55b172d57..0106eba46d5a 100644
--- a/fs/exportfs/expfs.c
+++ b/fs/exportfs/expfs.c
@@ -417,9 +417,11 @@ int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len,
 }
 EXPORT_SYMBOL_GPL(exportfs_encode_fh);
 
-struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
-		int fh_len, int fileid_type,
-		int (*acceptable)(void *, struct dentry *), void *context)
+struct dentry *
+exportfs_decode_fh_raw(struct vfsmount *mnt, struct fid *fid, int fh_len,
+		       int fileid_type,
+		       int (*acceptable)(void *, struct dentry *),
+		       void *context)
 {
 	const struct export_operations *nop = mnt->mnt_sb->s_export_op;
 	struct dentry *result, *alias;
@@ -432,10 +434,8 @@ struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
 	if (!nop || !nop->fh_to_dentry)
 		return ERR_PTR(-ESTALE);
 	result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);
-	if (PTR_ERR(result) == -ENOMEM)
-		return ERR_CAST(result);
 	if (IS_ERR_OR_NULL(result))
-		return ERR_PTR(-ESTALE);
+		return result;
 
 	/*
 	 * If no acceptance criteria was specified by caller, a disconnected
@@ -561,10 +561,26 @@ struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
 
  err_result:
 	dput(result);
-	if (err != -ENOMEM)
-		err = -ESTALE;
 	return ERR_PTR(err);
 }
+EXPORT_SYMBOL_GPL(exportfs_decode_fh_raw);
+
+struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
+				  int fh_len, int fileid_type,
+				  int (*acceptable)(void *, struct dentry *),
+				  void *context)
+{
+	struct dentry *ret;
+
+	ret = exportfs_decode_fh_raw(mnt, fid, fh_len, fileid_type,
+				     acceptable, context);
+	if (IS_ERR_OR_NULL(ret)) {
+		if (ret == ERR_PTR(-ENOMEM))
+			return ret;
+		return ERR_PTR(-ESTALE);
+	}
+	return ret;
+}
 EXPORT_SYMBOL_GPL(exportfs_decode_fh);
 
 MODULE_LICENSE("GPL");
diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
index d829403ffd3b..846df3c96730 100644
--- a/include/linux/exportfs.h
+++ b/include/linux/exportfs.h
@@ -223,6 +223,11 @@ extern int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid,
 				    int *max_len, struct inode *parent);
 extern int exportfs_encode_fh(struct dentry *dentry, struct fid *fid,
 	int *max_len, int connectable);
+extern struct dentry *exportfs_decode_fh_raw(struct vfsmount *mnt,
+					     struct fid *fid, int fh_len,
+					     int fileid_type,
+					     int (*acceptable)(void *, struct dentry *),
+					     void *context);
 extern struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid,
 	int fh_len, int fileid_type, int (*acceptable)(void *, struct dentry *),
 	void *context);
-- 
2.28.0

[PATCH v2 5/6] nfsd: Fix up nfsd to ensure that timeout errors don't result in ESTALE

[trondmy]

From: Trond Myklebust <trond.myklebust@hammerspace.com>

If the underlying filesystem times out, then we want knfsd to return
NFSERR_JUKEBOX/DELAY rather than NFSERR_STALE.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfsd/nfsfh.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
index 0c2ee65e46f3..46c86f7bc429 100644
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -268,12 +268,20 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp)
 	if (fileid_type == FILEID_ROOT)
 		dentry = dget(exp->ex_path.dentry);
 	else {
-		dentry = exportfs_decode_fh(exp->ex_path.mnt, fid,
-				data_left, fileid_type,
-				nfsd_acceptable, exp);
-		if (IS_ERR_OR_NULL(dentry))
+		dentry = exportfs_decode_fh_raw(exp->ex_path.mnt, fid,
+						data_left, fileid_type,
+						nfsd_acceptable, exp);
+		if (IS_ERR_OR_NULL(dentry)) {
 			trace_nfsd_set_fh_dentry_badhandle(rqstp, fhp,
 					dentry ?  PTR_ERR(dentry) : -ESTALE);
+			switch (PTR_ERR(dentry)) {
+			case -ENOMEM:
+			case -ETIMEDOUT:
+				break;
+			default:
+				dentry = ERR_PTR(-ESTALE);
+			}
+		}
 	}
 	if (dentry == NULL)
 		goto out;
-- 
2.28.0

[PATCH v2 6/6] nfsd: Set PF_LOCAL_THROTTLE on local filesystems only

[trondmy]

From: Trond Myklebust <trond.myklebust@hammerspace.com>

Don't set PF_LOCAL_THROTTLE on remote filesystems like NFS, since they
aren't expected to ever be subject to double buffering.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfs/export.c          |  3 ++-
 fs/nfsd/vfs.c            | 13 +++++++++++--
 include/linux/exportfs.h |  1 +
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/export.c b/fs/nfs/export.c
index 5428713af5fe..48b879cfe6e3 100644
--- a/fs/nfs/export.c
+++ b/fs/nfs/export.c
@@ -171,5 +171,6 @@ const struct export_operations nfs_export_ops = {
 	.encode_fh = nfs_encode_fh,
 	.fh_to_dentry = nfs_fh_to_dentry,
 	.get_parent = nfs_get_parent,
-	.flags = EXPORT_OP_NOWCC|EXPORT_OP_NOSUBTREECHK|EXPORT_OP_CLOSE_BEFORE_UNLINK,
+	.flags = EXPORT_OP_NOWCC|EXPORT_OP_NOSUBTREECHK|
+		EXPORT_OP_CLOSE_BEFORE_UNLINK|EXPORT_OP_REMOTE_FS,
 };
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 79cba942087e..04937e51de56 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -978,18 +978,25 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
 				__be32 *verf)
 {
 	struct file		*file = nf->nf_file;
+	struct super_block	*sb = file_inode(file)->i_sb;
 	struct svc_export	*exp;
 	struct iov_iter		iter;
 	__be32			nfserr;
 	int			host_err;
 	int			use_wgather;
 	loff_t			pos = offset;
+	unsigned long		exp_op_flags = 0;
 	unsigned int		pflags = current->flags;
 	rwf_t			flags = 0;
+	bool			restore_flags = false;
 
 	trace_nfsd_write_opened(rqstp, fhp, offset, *cnt);
 
-	if (test_bit(RQ_LOCAL, &rqstp->rq_flags))
+	if (sb->s_export_op)
+		exp_op_flags = sb->s_export_op->flags;
+
+	if (test_bit(RQ_LOCAL, &rqstp->rq_flags) &&
+	    !(exp_op_flags & EXPORT_OP_REMOTE_FS)) {
 		/*
 		 * We want throttling in balance_dirty_pages()
 		 * and shrink_inactive_list() to only consider
@@ -998,6 +1005,8 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
 		 * the client's dirty pages or its congested queue.
 		 */
 		current->flags |= PF_LOCAL_THROTTLE;
+		restore_flags = true;
+	}
 
 	exp = fhp->fh_export;
 	use_wgather = (rqstp->rq_vers == 2) && EX_WGATHER(exp);
@@ -1049,7 +1058,7 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
 		trace_nfsd_write_err(rqstp, fhp, offset, host_err);
 		nfserr = nfserrno(host_err);
 	}
-	if (test_bit(RQ_LOCAL, &rqstp->rq_flags))
+	if (restore_flags)
 		current_restore_flags(pflags, PF_LOCAL_THROTTLE);
 	return nfserr;
 }
diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
index 846df3c96730..d93e8a6737bb 100644
--- a/include/linux/exportfs.h
+++ b/include/linux/exportfs.h
@@ -216,6 +216,7 @@ struct export_operations {
 #define	EXPORT_OP_NOWCC			(0x1) /* don't collect v3 wcc data */
 #define	EXPORT_OP_NOSUBTREECHK		(0x2) /* no subtree checking */
 #define	EXPORT_OP_CLOSE_BEFORE_UNLINK	(0x4) /* close files before unlink */
+#define EXPORT_OP_REMOTE_FS		(0x8) /* Filesystem is remote */
 	unsigned long	flags;
 };
 
-- 
2.28.0