2023-07-16 19:11:23

by Christophe JAILLET

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 <[email protected]>
---
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

2023-07-17 02:31:55

by Joseph Qi

Subject: Re: [PATCH 1/2] ocfs2: Use flexible array in 'struct ocfs2_recovery_map'

On 7/17/23 2:48 AM, Christophe JAILLET wrote:
> 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 <[email protected]>

Looks fine.
Reviewed-by: Joseph Qi <[email protected]>


> ---
> 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[];
> };
>
>