libzfs.h: Set ZFS_MAXPROPLEN and ZPOOL_MAXPROPLEN to ZAP_MAXVALUELEN

So far, the values of ZFS_MAXPROPLEN and ZPOOL_MAXPROPLEN were equal to
MAXPATHLEN, which is 1024 on FreeBSD and 4096 on Linux. This wasn't
ideal. Some of the surprising outcomes of this implementation are:

1. When creating a pool user property with zpool-set(8), libzfs makes
   sure that the length of the property's value is less than
   ZFS_MAXPROPLEN. However, the ZFS kernel module does not do that.
   Instead, it checks the length against ZAP_MAXVALUELEN. As a result,
   it is possible to create a property the length of which is going to
   be larger than zpool(8) is ready to read.
2. A pool user property created on Linux is too big to be read on
   FreeBSD.

This change sets both ZFS_MAXPROPLEN and ZPOOL_MAXPROPLEN to
ZAP_MAXVALUELEN, which is 8192 at the moment.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Tino Reichardt <milky-zfs@mcmilk.de>
Reviewed-by: Allan Jude <allan@klarasystems.com>
Signed-off-by: Mateusz Piotrowski <0mp@FreeBSD.org>
Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Closes #16248

include/libzfs.h

@@ -51,8 +51,8 @@ extern "C" {
 /*
  * Miscellaneous ZFS constants
  */
-#define	ZFS_MAXPROPLEN		MAXPATHLEN
+#define	ZFS_MAXPROPLEN		ZAP_MAXVALUELEN
-#define	ZPOOL_MAXPROPLEN	MAXPATHLEN
+#define	ZPOOL_MAXPROPLEN	ZAP_MAXVALUELEN
 
 /*
  * libzfs errors

tests/zfs-tests/tests/functional/cli_root/zfs_clone/zfs_clone_010_pos.ksh

@@ -210,19 +210,15 @@ log_must local_cleanup
 log_note "verify clone list truncated correctly"
 fs=$TESTPOOL/$TESTFS1
 xs=""; for i in {1..200}; do xs+="x"; done
-if is_linux; then
+maxproplen=8192
-	ZFS_MAXPROPLEN=4096
-else
-	ZFS_MAXPROPLEN=1024
-fi
 log_must zfs create $fs
 log_must zfs snapshot $fs@snap
-for (( i = 1; i <= (ZFS_MAXPROPLEN / 200 + 1); i++ )); do
+for (( i = 1; i <= (maxproplen / 200 + 1); i++ )); do
 	log_must zfs clone ${fs}@snap ${fs}/${TESTCLONE}${xs}.${i}
 done
 clone_list=$(zfs list -o clones $fs@snap)
 char_count=$(echo "$clone_list" | tail -1 | wc -c)
-[[ $char_count -eq $ZFS_MAXPROPLEN ]] || \
+[[ $char_count -eq $maxproplen ]] || \
     log_fail "Clone list not truncated correctly. Unexpected character count" \
         "$char_count"
 

tests/zfs-tests/tests/functional/cli_root/zpool_set/user_property_001_pos.ksh

@@ -56,16 +56,10 @@ typeset -a values=()
 # for the null byte)
 names+=("$(awk 'BEGIN { printf "x:"; while (c++ < (256 - 2 - 1)) printf "a" }')")
 values+=("long-property-name")
-# Longest property value (the limits are 1024 on FreeBSD and 4096 on Linux, so
+# Longest property value (8191 bytes, which is the 8192-byte limit minus 1 byte
-# pick the right one; the longest value can use limit minus 1 bytes for the
+# for the null byte).
-# null byte)
-if is_linux; then
-	typeset ZFS_MAXPROPLEN=4096
-else
-	typeset ZFS_MAXPROPLEN=1024
-fi
 names+=("long:property:value")
-values+=("$(awk -v max="$ZFS_MAXPROPLEN" 'BEGIN { while (c++ < (max - 1)) printf "A" }')")
+values+=("$(awk 'BEGIN { while (c++ < (8192 - 1)) printf "A" }')")
 # Valid property names
 for i in {1..10}; do
 	typeset -i len

tests/zfs-tests/tests/functional/cli_root/zpool_set/user_property_002_neg.ksh

@@ -64,17 +64,11 @@ names+=("$(awk '
 	}'
 )")
 values+=("too-long-property-name")
-# A property value that is too long consists of at least 1024 bytes on FreeBSD
+# A property value that is too long consists of at least 8192 bytes.
-# and 4096 bytes on Linux.
 # The smallest too-long value is (1) the limit (2) minus 1 byte for the null
 # byte (2) plus 1 byte to reach back over the limit).
-if is_linux; then
-	typeset ZFS_MAXPROPLEN=4096
-else
-	typeset ZFS_MAXPROPLEN=1024
-fi
 names+=("too:long:property:value")
-values+=("$(awk -v max="$ZFS_MAXPROPLEN" 'BEGIN { while (c++ < (max - 1 + 1)) printf "A" }')")
+values+=("$(awk 'BEGIN { while (c++ < (8192 - 1 + 1)) printf "A" }')")
 # Invalid property names
 for i in {1..10}; do
 	typeset -i len