[Devel] [PATCH RHEL7 COMMIT] ext4: Module parameter to disable discard mount param on ploop

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-957.12.1.vz7.95.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-957.12.1.vz7.95.1
------>
commit 5263b9c619bd9f5b191b0bc1ab2ec734de17a4c5
Author: Kirill Tkhai <ktkhai at virtuozzo.com>
Date:   Sun Apr 28 23:49:41 2019 +0300

    ext4: Module parameter to disable discard mount param on ploop
    
    This is needed to measure performance in a standard way.
    
    https://jira.sw.ru/browse/PSBM-94181
    
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
---
 fs/ext4/super.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 623540274705..7f00f804cdba 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -117,6 +117,9 @@ MODULE_ALIAS("ext3");
 #define IS_EXT3_SB(sb) (0)
 #endif
 
+ushort ext4_force_discard_on_ploop = 1;
+module_param_named(force_discard_on_ploop, ext4_force_discard_on_ploop, ushort, 0644);
+
 static int ext4_verify_csum_type(struct super_block *sb,
 				 struct ext4_super_block *es)
 {
@@ -3974,7 +3977,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 		set_opt(sb, ERRORS_RO);
 	if (def_mount_opts & EXT4_DEFM_BLOCK_VALIDITY)
 		set_opt(sb, BLOCK_VALIDITY);
-	if (def_mount_opts & EXT4_DEFM_DISCARD || is_ploop(sb))
+	if (def_mount_opts & EXT4_DEFM_DISCARD || (is_ploop(sb) && ext4_force_discard_on_ploop))
 		set_opt(sb, DISCARD);
 
 	sbi->s_resuid = make_kuid(&init_user_ns, le16_to_cpu(es->s_def_resuid));