[{"id":3679068,"web_url":"http://patchwork.ozlabs.org/comment/3679068/","msgid":"<17C103A5-EE44-4762-AE7C-BA5E84F83D58@dilger.ca>","list_archive_url":null,"date":"2026-04-19T09:23:28","subject":"Re: [PATCH v2 v2 2/2] ext4: allow clearing mballoc stats through\n mb_stats","submitter":{"id":4514,"url":"http://patchwork.ozlabs.org/api/people/4514/","name":"Andreas Dilger","email":"adilger@dilger.ca"},"content":"On Apr 19, 2026, at 00:34, Baolin Liu <liubaolin12138@163.com> wrote:\n> \n> From: Baolin Liu <liubaolin@kylinos.cn>\n> \n> Make /proc/fs/ext4/<dev>/mb_stats writable and clear the runtime\n> mballoc statistics when 0 is written.\n> \n> Signed-off-by: Baolin Liu <liubaolin@kylinos.cn>\n\nReviewed-by: Andreas Dilger <adilger@dilger.ca <mailto:adilger@dilger.ca>>\n\n> ---\n> fs/ext4/ext4.h    |  1 +\n> fs/ext4/mballoc.c | 29 +++++++++++++++++++++++++++++\n> fs/ext4/sysfs.c   | 40 ++++++++++++++++++++++++++++++++++++++--\n> 3 files changed, 68 insertions(+), 2 deletions(-)\n> \n> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h\n> index 293f698b7042..3223e73612ae 100644\n> --- a/fs/ext4/ext4.h\n> +++ b/fs/ext4/ext4.h\n> @@ -2994,6 +2994,7 @@ int ext4_fc_record_regions(struct super_block *sb, int ino,\n> extern const struct seq_operations ext4_mb_seq_groups_ops;\n> extern const struct seq_operations ext4_mb_seq_structs_summary_ops;\n> extern int ext4_seq_mb_stats_show(struct seq_file *seq, void *offset);\n> +extern void ext4_mb_stats_clear(struct ext4_sb_info *sbi);\n> extern int ext4_mb_init(struct super_block *);\n> extern void ext4_mb_release(struct super_block *);\n> extern ext4_fsblk_t ext4_mb_new_blocks(handle_t *,\n> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c\n> index 1e13ef62cb9d..79ddfa935813 100644\n> --- a/fs/ext4/mballoc.c\n> +++ b/fs/ext4/mballoc.c\n> @@ -4723,6 +4723,35 @@ static void ext4_mb_collect_stats(struct ext4_allocation_context *ac)\n> trace_ext4_mballoc_prealloc(ac);\n> }\n> \n> +void ext4_mb_stats_clear(struct ext4_sb_info *sbi)\n> +{\n> +\tint i;\n> +\n> +\tatomic_set(&sbi->s_bal_reqs, 0);\n> +\tatomic_set(&sbi->s_bal_success, 0);\n> +\tatomic_set(&sbi->s_bal_allocated, 0);\n> +\tatomic_set(&sbi->s_bal_groups_scanned, 0);\n> +\n> +\tfor (i = 0; i < EXT4_MB_NUM_CRS; i++) {\n> +\t\tatomic64_set(&sbi->s_bal_cX_hits[i], 0);\n> +\t\tatomic64_set(&sbi->s_bal_cX_groups_considered[i], 0);\n> +\t\tatomic_set(&sbi->s_bal_cX_ex_scanned[i], 0);\n> +\t\tatomic64_set(&sbi->s_bal_cX_failed[i], 0);\n> +\t}\n> +\n> +\tatomic_set(&sbi->s_bal_ex_scanned, 0);\n> +\tatomic_set(&sbi->s_bal_goals, 0);\n> +\tatomic_set(&sbi->s_bal_stream_goals, 0);\n> +\tatomic_set(&sbi->s_bal_len_goals, 0);\n> +\tatomic_set(&sbi->s_bal_2orders, 0);\n> +\tatomic_set(&sbi->s_bal_breaks, 0);\n> +\tatomic_set(&sbi->s_mb_lost_chunks, 0);\n> +\tatomic_set(&sbi->s_mb_buddies_generated, 0);\n> +\tatomic64_set(&sbi->s_mb_generation_time, 0);\n> +\tatomic_set(&sbi->s_mb_preallocated, 0);\n> +\tatomic_set(&sbi->s_mb_discarded, 0);\n> +}\n> +\n> /*\n>  * Called on failure; free up any blocks from the inode PA for this\n>  * context.  We don't need this for MB_GROUP_PA because we only change\n> diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c\n> index b87d7bdab06a..e90885d470ab 100644\n> --- a/fs/ext4/sysfs.c\n> +++ b/fs/ext4/sysfs.c\n> @@ -52,6 +52,42 @@ typedef enum {\n> static const char proc_dirname[] = \"fs/ext4\";\n> static struct proc_dir_entry *ext4_proc_root;\n> \n> +static int ext4_mb_stats_open(struct inode *inode, struct file *file)\n> +{\n> +\treturn single_open(file, ext4_seq_mb_stats_show, pde_data(inode));\n> +}\n> +\n> +static ssize_t ext4_mb_stats_write(struct file *file, const char __user *buf,\n> +\t\t\t\t   size_t count, loff_t *ppos)\n> +{\n> +\tstruct super_block *sb = pde_data(file_inode(file));\n> +\tchar kbuf[2];\n> +\n> +\tif (count == 0 || count > sizeof(kbuf))\n> +\t\treturn -EINVAL;\n> +\n> +\tif (copy_from_user(kbuf, buf, count))\n> +\t\treturn -EFAULT;\n> +\n> +\tif (count == 2) {\n> +\t\tif (kbuf[0] != '0' || kbuf[1] != '\\n')\n> +\t\t\treturn -EINVAL;\n> +\t} else if (kbuf[0] != '0') {\n> +\t\treturn -EINVAL;\n> +\t}\n> +\n> +\text4_mb_stats_clear(EXT4_SB(sb));\n> +\treturn count;\n> +}\n> +\n> +static const struct proc_ops ext4_mb_stats_proc_ops = {\n> +\t.proc_open\t= ext4_mb_stats_open,\n> +\t.proc_read\t= seq_read,\n> +\t.proc_lseek\t= seq_lseek,\n> +\t.proc_release\t= single_release,\n> +\t.proc_write\t= ext4_mb_stats_write,\n> +};\n> +\n>  struct ext4_attr {\n>  \tstruct attribute attr;\n>  \tshort attr_id;\n> @@ -630,8 +666,8 @@ int ext4_register_sysfs(struct super_block *sb)\n>  \t\t\t\t\text4_fc_info_show, sb);\n>  \t\tproc_create_seq_data(\"mb_groups\", S_IRUGO, sbi->s_proc,\n>  \t\t\t\t&ext4_mb_seq_groups_ops, sb);\n> -\t\tproc_create_single_data(\"mb_stats\", 0444, sbi->s_proc,\n> -\t\t\t\text4_seq_mb_stats_show, sb);\n> +\t\tproc_create_data(\"mb_stats\", 0644, sbi->s_proc,\n> +\t\t\t\t &ext4_mb_stats_proc_ops, sb);\n>  \t\tproc_create_seq_data(\"mb_structs_summary\", 0444, sbi->s_proc,\n>  \t\t\t\t&ext4_mb_seq_structs_summary_ops, sb);\n> }\n> -- \n> 2.51.0\n> \n\n\nCheers, Andreas","headers":{"Return-Path":"\n <SRS0=XkdN=CS=vger.kernel.org=linux-ext4+bounces-15906-patchwork-incoming=ozlabs.org@ozlabs.org>","X-Original-To":["incoming@patchwork.ozlabs.org","linux-ext4@vger.kernel.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","patchwork-incoming@ozlabs.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=dilger-ca.20251104.gappssmtp.com\n header.i=@dilger-ca.20251104.gappssmtp.com header.a=rsa-sha256\n header.s=20251104 header.b=S0PgM7wO;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=ozlabs.org\n (client-ip=150.107.74.76; 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Well, I guess if you are looking at this file you are\nanyways debugging kernel code so that should be fine\n\nFeel free to add:\n\nOjaswin Mujoo <ojaswin@linux.ibm.com>\n\nRegards,\nojaswin\n\n\n>  fs/ext4/ext4.h    |  1 +\n>  fs/ext4/mballoc.c | 29 +++++++++++++++++++++++++++++\n>  fs/ext4/sysfs.c   | 40 ++++++++++++++++++++++++++++++++++++++--\n>  3 files changed, 68 insertions(+), 2 deletions(-)\n>","headers":{"Return-Path":"\n <SRS0=Wt16=CT=vger.kernel.org=linux-ext4+bounces-15910-patchwork-incoming=ozlabs.org@ozlabs.org>","X-Original-To":["incoming@patchwork.ozlabs.org","linux-ext4@vger.kernel.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","patchwork-incoming@ozlabs.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256\n header.s=pp1 header.b=OOCt5gjr;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=ozlabs.org\n (client-ip=150.107.74.76; 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