nfs: fix incorrect error handling in LOCALIO

nfs4_stat_to_errno() expects a NFSv4 error code as an argument and
returns a POSIX errno.

The problem is LOCALIO is passing nfs4_stat_to_errno() the POSIX errno
return values from filp->f_op->read_iter(), filp->f_op->write_iter()
and vfs_fsync_range().

So the POSIX errno that nfs_local_pgio_done() and
nfs_local_commit_done() are passing to nfs4_stat_to_errno() are
failing to match any NFSv4 error code, which results in
nfs4_stat_to_errno() defaulting to returning -EREMOTEIO. This causes
assertions in upper layers due to -EREMOTEIO not being a valid NFSv4
error code.

Fix this by updating nfs_local_pgio_done() and nfs_local_commit_done()
to use the new nfs_localio_errno_to_nfs4_stat() to map a POSIX errno
to an NFSv4 error code.

Care was taken to factor out nfs4_errtbl_common[] to avoid duplicating
the same NFS error to errno table. nfs4_errtbl_common[] is checked
first by both nfs4_stat_to_errno and nfs_localio_errno_to_nfs4_stat
before they check their own more specialized tables (nfs4_errtbl[] and
nfs4_errtbl_localio[] respectively).

While auditing the associated error mapping tables, the (ab)use of -1
for the last table entry was removed in favor of using ARRAY_SIZE to
iterate the nfs_errtbl[] and nfs4_errtbl[]. And 'errno_NFSERR_IO' was
removed because it caused needless obfuscation.

Fixes: 70ba381 ("nfs: add LOCALIO support")
Reported-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>

Author: Mike Snitzer

fs/nfs/localio.c

@@ -388,7 +388,7 @@ nfs_local_pgio_done(struct nfs_pgio_header *hdr, long status)
 		hdr->res.op_status = NFS4_OK;
 		hdr->task.tk_status = 0;
 	} else {
-		hdr->res.op_status = nfs4_stat_to_errno(status);
+		hdr->res.op_status = nfs_localio_errno_to_nfs4_stat(status);
 		hdr->task.tk_status = status;
 	}
 }
@@ -786,7 +786,7 @@ nfs_local_commit_done(struct nfs_commit_data *data, int status)
 		data->task.tk_status = 0;
 	} else {
 		nfs_reset_boot_verifier(data->inode);
-		data->res.op_status = nfs4_stat_to_errno(status);
+		data->res.op_status = nfs_localio_errno_to_nfs4_stat(status);
 		data->task.tk_status = status;
 	}
 }

fs/nfs_common/common.c

@@ -15,7 +15,7 @@ static const struct {
 	{ NFS_OK,		0		},
 	{ NFSERR_PERM,		-EPERM		},
 	{ NFSERR_NOENT,		-ENOENT		},
-	{ NFSERR_IO,		-errno_NFSERR_IO},
+	{ NFSERR_IO,		-EIO		},
 	{ NFSERR_NXIO,		-ENXIO		},
 /*	{ NFSERR_EAGAIN,	-EAGAIN		}, */
 	{ NFSERR_ACCES,		-EACCES		},
@@ -45,7 +45,6 @@ static const struct {
 	{ NFSERR_SERVERFAULT,	-EREMOTEIO	},
 	{ NFSERR_BADTYPE,	-EBADTYPE	},
 	{ NFSERR_JUKEBOX,	-EJUKEBOX	},
-	{ -1,			-EIO		}
 };
 
 /**
@@ -59,26 +58,29 @@ int nfs_stat_to_errno(enum nfs_stat status)
 {
 	int i;
 
-	for (i = 0; nfs_errtbl[i].stat != -1; i++) {
+	for (i = 0; i < ARRAY_SIZE(nfs_errtbl); i++) {
 		if (nfs_errtbl[i].stat == (int)status)
 			return nfs_errtbl[i].errno;
 	}
-	return nfs_errtbl[i].errno;
+	return -EIO;
 }
 EXPORT_SYMBOL_GPL(nfs_stat_to_errno);
 
 /*
  * We need to translate between nfs v4 status return values and
  * the local errno values which may not be the same.
+ *
+ * nfs4_errtbl_common[] is used before more specialized mappings
+ * available in nfs4_errtbl[] or nfs4_errtbl_localio[].
  */
 static const struct {
 	int stat;
 	int errno;
-} nfs4_errtbl[] = {
+} nfs4_errtbl_common[] = {
 	{ NFS4_OK,		0		},
 	{ NFS4ERR_PERM,		-EPERM		},
 	{ NFS4ERR_NOENT,	-ENOENT		},
-	{ NFS4ERR_IO,		-errno_NFSERR_IO},
+	{ NFS4ERR_IO,		-EIO		},
 	{ NFS4ERR_NXIO,		-ENXIO		},
 	{ NFS4ERR_ACCESS,	-EACCES		},
 	{ NFS4ERR_EXIST,	-EEXIST		},
@@ -98,15 +100,20 @@ static const struct {
 	{ NFS4ERR_BAD_COOKIE,	-EBADCOOKIE	},
 	{ NFS4ERR_NOTSUPP,	-ENOTSUPP	},
 	{ NFS4ERR_TOOSMALL,	-ETOOSMALL	},
-	{ NFS4ERR_SERVERFAULT,	-EREMOTEIO	},
 	{ NFS4ERR_BADTYPE,	-EBADTYPE	},
-	{ NFS4ERR_LOCKED,	-EAGAIN		},
 	{ NFS4ERR_SYMLINK,	-ELOOP		},
-	{ NFS4ERR_OP_ILLEGAL,	-EOPNOTSUPP	},
 	{ NFS4ERR_DEADLOCK,	-EDEADLK	},
+};
+
+static const struct {
+	int stat;
+	int errno;
+} nfs4_errtbl[] = {
+	{ NFS4ERR_SERVERFAULT,	-EREMOTEIO	},
+	{ NFS4ERR_LOCKED,	-EAGAIN		},
+	{ NFS4ERR_OP_ILLEGAL,	-EOPNOTSUPP	},
 	{ NFS4ERR_NOXATTR,	-ENODATA	},
 	{ NFS4ERR_XATTR2BIG,	-E2BIG		},
-	{ -1,			-EIO		}
 };
 
 /*
@@ -116,7 +123,14 @@ static const struct {
 int nfs4_stat_to_errno(int stat)
 {
 	int i;
-	for (i = 0; nfs4_errtbl[i].stat != -1; i++) {
+
+	/* First check nfs4_errtbl_common */
+	for (i = 0; i < ARRAY_SIZE(nfs4_errtbl_common); i++) {
+		if (nfs4_errtbl_common[i].stat == stat)
+			return nfs4_errtbl_common[i].errno;
+	}
+	/* Then check nfs4_errtbl */
+	for (i = 0; i < ARRAY_SIZE(nfs4_errtbl); i++) {
 		if (nfs4_errtbl[i].stat == stat)
 			return nfs4_errtbl[i].errno;
 	}
@@ -132,3 +146,56 @@ int nfs4_stat_to_errno(int stat)
 	return -stat;
 }
 EXPORT_SYMBOL_GPL(nfs4_stat_to_errno);
+
+/*
+ * This table is useful for conversion from local errno to NFS error.
+ * It provides more logically correct mappings for use with LOCALIO
+ * (which is focused on converting from errno to NFS status).
+ */
+static const struct {
+	int stat;
+	int errno;
+} nfs4_errtbl_localio[] = {
+	/* Map errors differently than nfs4_errtbl */
+	{ NFS4ERR_IO,		-EREMOTEIO	},
+	{ NFS4ERR_DELAY,	-EAGAIN		},
+	{ NFS4ERR_FBIG,		-E2BIG		},
+	/* Map errors not handled by nfs4_errtbl */
+	{ NFS4ERR_STALE,	-EBADF		},
+	{ NFS4ERR_STALE,	-EOPENSTALE	},
+	{ NFS4ERR_DELAY,	-ETIMEDOUT	},
+	{ NFS4ERR_DELAY,	-ERESTARTSYS	},
+	{ NFS4ERR_DELAY,	-ENOMEM		},
+	{ NFS4ERR_IO,		-ETXTBSY	},
+	{ NFS4ERR_IO,		-EBUSY		},
+	{ NFS4ERR_SERVERFAULT,	-ESERVERFAULT	},
+	{ NFS4ERR_SERVERFAULT,	-ENFILE		},
+	{ NFS4ERR_IO,		-EUCLEAN	},
+	{ NFS4ERR_PERM,		-ENOKEY		},
+};
+
+/*
+ * Convert an errno to an NFS error code for LOCALIO.
+ */
+__u32 nfs_localio_errno_to_nfs4_stat(int errno)
+{
+	int i;
+
+	/* First check nfs4_errtbl_common */
+	for (i = 0; i < ARRAY_SIZE(nfs4_errtbl_common); i++) {
+		if (nfs4_errtbl_common[i].errno == errno)
+			return nfs4_errtbl_common[i].stat;
+	}
+	/* Then check nfs4_errtbl_localio */
+	for (i = 0; i < ARRAY_SIZE(nfs4_errtbl_localio); i++) {
+		if (nfs4_errtbl_localio[i].errno == errno)
+			return nfs4_errtbl_localio[i].stat;
+	}
+	/* If we cannot translate the error, the recovery routines should
+	 * handle it.
+	 * Note: remaining NFSv4 error codes have values > 10000, so should
+	 * not conflict with native Linux error codes.
+	 */
+	return NFS4ERR_SERVERFAULT;
+}
+EXPORT_SYMBOL_GPL(nfs_localio_errno_to_nfs4_stat);

include/linux/nfs_common.h

@@ -9,9 +9,10 @@
 #include <uapi/linux/nfs.h>
 
 /* Mapping from NFS error code to "errno" error code. */
-#define errno_NFSERR_IO EIO
 
 int nfs_stat_to_errno(enum nfs_stat status);
 int nfs4_stat_to_errno(int stat);
 
+__u32 nfs_localio_errno_to_nfs4_stat(int errno);
+
 #endif /* _LINUX_NFS_COMMON_H */