On Thu, 30 Oct 2025 20:33:21 +0800
Li Chen <[email protected]> wrote:
> From: Li Chen <[email protected]>
>
> Before this change pcache_meta_find_latest() was copying each
> slot directly into meta_ret while scanning. If no valid slot
> was found and the function returned NULL, meta_ret still held
> whatever was last copied (possibly CRC-bad). Later users
> (e.g. cache_segs_init) could mistakenly trust that data.
>
> Allocate a temporary buffer instead and only populate meta_ret after a
> valid/latest header is found. If no valid header exists we return NULL
> without touching meta_ret.
>
> Also add __free(kvfree) so the temporary buffer is always freed, and
> include the needed headers.
>
> Signed-off-by: Li Chen <[email protected]>
> ---
> drivers/md/dm-pcache/pcache_internal.h | 13 +++++++++----
> 1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/md/dm-pcache/pcache_internal.h
> b/drivers/md/dm-pcache/pcache_internal.h
> index b7a3319d2bd3e..ac28f9dd2986f 100644
> --- a/drivers/md/dm-pcache/pcache_internal.h
> +++ b/drivers/md/dm-pcache/pcache_internal.h
> @@ -4,6 +4,8 @@
>
> #include <linux/delay.h>
> #include <linux/crc32c.h>
> +#include <linux/slab.h>
> +#include <linux/cleanup.h>
>
> #define pcache_err(fmt, ...)
> \
> pr_err("dm-pcache: %s:%u " fmt, __func__, __LINE__, ##__VA_ARGS__)
> @@ -79,14 +81,17 @@ static inline void __must_check
> *pcache_meta_find_latest(struct pcache_meta_head
> u32 meta_size, u32 meta_max_size,
> void *meta_ret)
> {
> - struct pcache_meta_header *meta, *latest = NULL;
> + struct pcache_meta_header *latest = NULL;
> + struct pcache_meta_header *meta __free(kvfree);
> u32 i, seq_latest = 0;
> - void *meta_addr;
>
> - meta = meta_ret;
> + meta = kvzalloc(meta_size, GFP_KERNEL);
See the guidance notes in cleanup.h THis hsould be
struct pcache_meta_header *meta __free(kvfree) =
kvzalloc(meta_size, GFP_KERNEL);
That is the constructor and destructor must be together. Inline variable
declarations are fine for this one type of use.
> + if (!meta)
> + return ERR_PTR(-ENOMEM);
>
> for (i = 0; i < PCACHE_META_INDEX_MAX; i++) {
> - meta_addr = (void *)header + (i * meta_max_size);
> + void *meta_addr = (void *)header + (i * meta_max_size);
> +
> if (copy_mc_to_kernel(meta, meta_addr, meta_size)) {
> pcache_err("hardware memory error when copy meta");
> return ERR_PTR(-EIO);
