linux-kernel - [PATCH 1/2] ocfs2: Use flexible array in 'struct ocfs2_recovery

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Message-Id: <c645911ffd2720fce5e344c17de642518cd0db52.1689533270.git.christophe.jaillet@wanadoo.fr>
Date:   Sun, 16 Jul 2023 20:48:56 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Mark Fasheh <mark@...heh.com>, Joel Becker <jlbec@...lplan.org>,
        Joseph Qi <joseph.qi@...ux.alibaba.com>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        ocfs2-devel@...ts.linux.dev
Subject: [PATCH 1/2] ocfs2: Use flexible array in 'struct ocfs2_recovery_map'

Turn 'rm_entries' in 'struct ocfs2_recovery_map' into a flexible array.

The advantages are:
   - save the size of a pointer when the new undo structure is allocated
   - avoid some always ugly pointer arithmetic to get the address of
    'rm_entries'
   - avoid an indirection when the array is accessed

While at it, use struct_size() to compute the size of the new undo
structure.

Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
---
 fs/ocfs2/journal.c | 5 +----
 fs/ocfs2/journal.h | 2 +-
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/fs/ocfs2/journal.c b/fs/ocfs2/journal.c
index 25d8072ccfce..2f7e70109020 100644
--- a/fs/ocfs2/journal.c
+++ b/fs/ocfs2/journal.c
@@ -178,16 +178,13 @@ int ocfs2_recovery_init(struct ocfs2_super *osb)
 	osb->recovery_thread_task = NULL;
 	init_waitqueue_head(&osb->recovery_event);
 
-	rm = kzalloc(sizeof(struct ocfs2_recovery_map) +
-		     osb->max_slots * sizeof(unsigned int),
+	rm = kzalloc(struct_size(rm, rm_entries, osb->max_slots),
 		     GFP_KERNEL);
 	if (!rm) {
 		mlog_errno(-ENOMEM);
 		return -ENOMEM;
 	}
 
-	rm->rm_entries = (unsigned int *)((char *)rm +
-					  sizeof(struct ocfs2_recovery_map));
 	osb->recovery_map = rm;
 
 	return 0;
diff --git a/fs/ocfs2/journal.h b/fs/ocfs2/journal.h
index 41c382f68529..41c9fe7e62f9 100644
--- a/fs/ocfs2/journal.h
+++ b/fs/ocfs2/journal.h
@@ -29,7 +29,7 @@ struct ocfs2_dinode;
 
 struct ocfs2_recovery_map {
 	unsigned int rm_used;
-	unsigned int *rm_entries;
+	unsigned int rm_entries[];
 };
 
 
-- 
2.34.1