From 010df42bf56ec012dfcdf9ff984efc4843796b44 Mon Sep 17 00:00:00 2001
From: Mauricio Faria de Oliveira <mfo@canonical.com>
Date: Tue, 19 Nov 2019 20:05:54 +0000
Subject: [PATCH] Check for unlinked znodes after igrab()

The changes in commit 41e1aa2a / PR#9583 introduced a regression on
tmpfile_001_pos: fsetxattr() on a O_TMPFILE file descriptor started
to fail with errno ENODATA:

    openat(AT_FDCWD, "/test", O_RDWR|O_TMPFILE, 0666) = 3
    <...>
    fsetxattr(3, "user.test", <...>, 64, 0) = -1 ENODATA

The originally proposed change on PR#9583 is not susceptible to it,
so just move the code/if-checks around back in that way, to fix it.

    $ export TESTDIR="/test"  # zfs mountpoint

Before that commit:

    $ cat /sys/module/zfs/version
    0.8.0-401_gcc1a1e17

    $ /usr/share/zfs/zfs-tests/tests/functional/tmpfile/tmpfile_001_pos
    Verify O_TMPFILE is working properly.

    $ echo $?
    0

After that commit:

    $ cat /sys/module/zfs/version
    0.8.0-402_g41e1aa2a

    $ /usr/share/zfs/zfs-tests/tests/functional/tmpfile/tmpfile_001_pos
    Verify O_TMPFILE is working properly.
    fsetxattr: No data available

    $ echo $?
    6

With this commit:

    $ cat /sys/module/zfs/version
    0.8.0-405_g...

    $ /usr/share/zfs/zfs-tests/tests/functional/tmpfile/tmpfile_001_pos
    Verify O_TMPFILE is working properly.

    $ echo $?
    0

Original-patch-by: Heitor Alves de Siqueira <halves@canonical.com>
Signed-off-by: Mauricio Faria de Oliveira <mfo@canonical.com>
---
 module/os/linux/zfs/zfs_znode.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/module/os/linux/zfs/zfs_znode.c b/module/os/linux/zfs/zfs_znode.c
index c623d61f7066..30ceccc2b57b 100644
--- a/module/os/linux/zfs/zfs_znode.c
+++ b/module/os/linux/zfs/zfs_znode.c
@@ -1095,7 +1095,8 @@ zfs_zget(zfsvfs_t *zfsvfs, uint64_t obj_num, znode_t **zpp)
 		ASSERT3U(zp->z_id, ==, obj_num);
 		/*
 		 * If zp->z_unlinked is set, the znode is already marked
-		 * for deletion and should not be discovered.
+		 * for deletion and should not be discovered. Check this
+		 * after checking igrab() due to fsetxattr() & O_TMPFILE.
 		 *
 		 * If igrab() returns NULL the VFS has independently
 		 * determined the inode should be evicted and has
@@ -1110,10 +1111,11 @@ zfs_zget(zfsvfs_t *zfsvfs, uint64_t obj_num, znode_t **zpp)
 		 * need to detect the active SA hold thereby informing
 		 * the VFS that this inode should not be evicted.
 		 */
-		if (zp->z_unlinked) {
-			err = SET_ERROR(ENOENT);
-		} else if (igrab(ZTOI(zp)) == NULL) {
-			err = SET_ERROR(EAGAIN);
+		if (igrab(ZTOI(zp)) == NULL) {
+			if (zp->z_unlinked)
+				err = SET_ERROR(ENOENT);
+			else
+				err = SET_ERROR(EAGAIN);
 		} else {
 			*zpp = zp;
 			err = 0;