linux-kernel - [PATCH 5.17 141/146] ext4: update the cached overhead value in the superblock

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Date:   Tue, 26 Apr 2022 10:22:16 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Theodore Tso <tytso@....edu>,
        stable@...nel.org
Subject: [PATCH 5.17 141/146] ext4: update the cached overhead value in the superblock

From: Theodore Ts'o <tytso@....edu>

commit eb7054212eac8b451d727bf079eae3db8c88f9d3 upstream.

If we (re-)calculate the file system overhead amount and it's
different from the on-disk s_overhead_clusters value, update the
on-disk version since this can take potentially quite a while on
bigalloc file systems.

Signed-off-by: Theodore Ts'o <tytso@....edu>
Cc: stable@...nel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 fs/ext4/ext4.h  |    1 +
 fs/ext4/ioctl.c |   16 ++++++++++++++++
 fs/ext4/super.c |    2 ++
 3 files changed, 19 insertions(+)

--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -3066,6 +3066,7 @@ int ext4_fileattr_set(struct user_namesp
 		      struct dentry *dentry, struct fileattr *fa);
 int ext4_fileattr_get(struct dentry *dentry, struct fileattr *fa);
 extern void ext4_reset_inode_seed(struct inode *inode);
+int ext4_update_overhead(struct super_block *sb);
 
 /* migrate.c */
 extern int ext4_ext_migrate(struct inode *);
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -1652,3 +1652,19 @@ long ext4_compat_ioctl(struct file *file
 	return ext4_ioctl(file, cmd, (unsigned long) compat_ptr(arg));
 }
 #endif
+
+static void set_overhead(struct ext4_super_block *es, const void *arg)
+{
+	es->s_overhead_clusters = cpu_to_le32(*((unsigned long *) arg));
+}
+
+int ext4_update_overhead(struct super_block *sb)
+{
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+
+	if (sb_rdonly(sb) || sbi->s_overhead == 0 ||
+	    sbi->s_overhead == le32_to_cpu(sbi->s_es->s_overhead_clusters))
+		return 0;
+
+	return ext4_update_superblocks_fn(sb, set_overhead, &sbi->s_overhead);
+}
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5597,6 +5597,8 @@ static int ext4_fill_super(struct super_
 		ext4_msg(sb, KERN_INFO, "mounted filesystem with%s. "
 			 "Quota mode: %s.", descr, ext4_quota_mode(sb));
 
+	/* Update the s_overhead_clusters if necessary */
+	ext4_update_overhead(sb);
 	return 0;
 
 free_sbi: