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Subject[PATCH 1/2] ext4: Make mb_optimize_scan option work with set/unset mount cmd
Date
After moving to the new mount API, mb_optimize_scan mount option
handling was not working as expected due to the parsed value always
being overwritten by default. Refactor and fix this to the expected
behavior described below:

* mb_optimize_scan=1 - On
* mb_optimize_scan=0 - Off
* mb_optimize_scan not passed - On if no. of BGs > threshold else off
* Remounts retain previous value unless we explicitly pass the option
with a new value

Reported-by: Ritesh Harjani <riteshh@linux.ibm.com>
Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
---
fs/ext4/super.c | 24 ++++++++++++++----------
1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index c5021ca0a28a..cd0547fabd79 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2021,12 +2021,12 @@ static int ext4_set_test_dummy_encryption(struct super_block *sb, char *arg)
#define EXT4_SPEC_s_commit_interval (1 << 16)
#define EXT4_SPEC_s_fc_debug_max_replay (1 << 17)
#define EXT4_SPEC_s_sb_block (1 << 18)
+#define EXT4_SPEC_mb_optimize_scan (1 << 19)

struct ext4_fs_context {
char *s_qf_names[EXT4_MAXQUOTAS];
char *test_dummy_enc_arg;
int s_jquota_fmt; /* Format of quota to use */
- int mb_optimize_scan;
#ifdef CONFIG_EXT4_DEBUG
int s_fc_debug_max_replay;
#endif
@@ -2451,12 +2451,17 @@ static int ext4_parse_param(struct fs_context *fc, struct fs_parameter *param)
ctx_clear_mount_opt(ctx, m->mount_opt);
return 0;
case Opt_mb_optimize_scan:
- if (result.int_32 != 0 && result.int_32 != 1) {
+ if (result.int_32 == 1) {
+ ctx_set_mount_opt2(ctx, EXT4_MOUNT2_MB_OPTIMIZE_SCAN);
+ ctx->spec |= EXT4_SPEC_mb_optimize_scan;
+ } else if (result.int_32 == 0) {
+ ctx_clear_mount_opt2(ctx, EXT4_MOUNT2_MB_OPTIMIZE_SCAN);
+ ctx->spec |= EXT4_SPEC_mb_optimize_scan;
+ } else {
ext4_msg(NULL, KERN_WARNING,
"mb_optimize_scan should be set to 0 or 1.");
return -EINVAL;
}
- ctx->mb_optimize_scan = result.int_32;
return 0;
}

@@ -4369,7 +4374,6 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)

/* Set defaults for the variables that will be set during parsing */
ctx->journal_ioprio = DEFAULT_JOURNAL_IOPRIO;
- ctx->mb_optimize_scan = DEFAULT_MB_OPTIMIZE_SCAN;

sbi->s_inode_readahead_blks = EXT4_DEF_INODE_READAHEAD_BLKS;
sbi->s_sectors_written_start =
@@ -5320,12 +5324,12 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
* turned off by passing "mb_optimize_scan=0". This can also be
* turned on forcefully by passing "mb_optimize_scan=1".
*/
- if (ctx->mb_optimize_scan == 1)
- set_opt2(sb, MB_OPTIMIZE_SCAN);
- else if (ctx->mb_optimize_scan == 0)
- clear_opt2(sb, MB_OPTIMIZE_SCAN);
- else if (sbi->s_groups_count >= MB_DEFAULT_LINEAR_SCAN_THRESHOLD)
- set_opt2(sb, MB_OPTIMIZE_SCAN);
+ if (!(ctx->spec & EXT4_SPEC_mb_optimize_scan)) {
+ if (sbi->s_groups_count >= MB_DEFAULT_LINEAR_SCAN_THRESHOLD)
+ set_opt2(sb, MB_OPTIMIZE_SCAN);
+ else
+ clear_opt2(sb, MB_OPTIMIZE_SCAN);
+ }

err = ext4_mb_init(sb);
if (err) {
--
2.27.0
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