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/* SPDX-License-Identifier: GPL-2.0-or-later */
#ifndef _PCACHE_INTERNAL_H
#define _PCACHE_INTERNAL_H
#include <linux/delay.h>
#include <linux/crc32c.h>
#define pcache_err(fmt, ...) \
pr_err("dm-pcache: %s:%u " fmt, __func__, __LINE__, ##__VA_ARGS__)
#define pcache_info(fmt, ...) \
pr_info("dm-pcache: %s:%u " fmt, __func__, __LINE__, ##__VA_ARGS__)
#define pcache_debug(fmt, ...) \
pr_debug("dm-pcache: %s:%u " fmt, __func__, __LINE__, ##__VA_ARGS__)
#define PCACHE_KB (1024ULL)
#define PCACHE_MB (1024 * PCACHE_KB)
/* Maximum number of metadata indices */
#define PCACHE_META_INDEX_MAX 2
#define PCACHE_CRC_SEED 0x3B15A
/*
* struct pcache_meta_header - PCACHE metadata header structure
* @crc: CRC checksum for validating metadata integrity.
* @seq: Sequence number to track metadata updates.
* @version: Metadata version.
* @res: Reserved space for future use.
*/
struct pcache_meta_header {
__u32 crc;
__u8 seq;
__u8 version;
__u16 res;
};
/*
* pcache_meta_crc - Calculate CRC for the given metadata header.
* @header: Pointer to the metadata header.
* @meta_size: Size of the metadata structure.
*
* Returns the CRC checksum calculated by excluding the CRC field itself.
*/
static inline u32 pcache_meta_crc(struct pcache_meta_header *header, u32 meta_size)
{
return crc32c(PCACHE_CRC_SEED, (void *)header + 4, meta_size - 4);
}
/*
* pcache_meta_seq_after - Check if a sequence number is more recent, accounting for overflow.
* @seq1: First sequence number.
* @seq2: Second sequence number.
*
* Determines if @seq1 is more recent than @seq2 by calculating the signed
* difference between them. This approach allows handling sequence number
* overflow correctly because the difference wraps naturally, and any value
* greater than zero indicates that @seq1 is "after" @seq2. This method
* assumes 8-bit unsigned sequence numbers, where the difference wraps
* around if seq1 overflows past seq2.
*
* Returns:
* - true if @seq1 is more recent than @seq2, indicating it comes "after"
* - false otherwise.
*/
static inline bool pcache_meta_seq_after(u8 seq1, u8 seq2)
{
return (s8)(seq1 - seq2) > 0;
}
/*
* pcache_meta_find_latest - Find the latest valid metadata.
* @header: Pointer to the metadata header.
* @meta_size: Size of each metadata block.
*
* Finds the latest valid metadata by checking sequence numbers. If a
* valid entry with the highest sequence number is found, its pointer
* is returned. Returns NULL if no valid metadata is found.
*/
static inline void __must_check *pcache_meta_find_latest(struct pcache_meta_header *header,
u32 meta_size, u32 meta_max_size,
void *meta_ret)
{
struct pcache_meta_header *meta, *latest = NULL;
u32 i, seq_latest = 0;
void *meta_addr;
meta = meta_ret;
for (i = 0; i < PCACHE_META_INDEX_MAX; i++) {
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);
}
/* Skip if CRC check fails, which means corrupted */
if (meta->crc != pcache_meta_crc(meta, meta_size))
continue;
/* Update latest if a more recent sequence is found */
if (!latest || pcache_meta_seq_after(meta->seq, seq_latest)) {
seq_latest = meta->seq;
latest = (void *)header + (i * meta_max_size);
}
}
if (!latest)
return NULL;
if (copy_mc_to_kernel(meta_ret, latest, meta_size)) {
pcache_err("hardware memory error");
return ERR_PTR(-EIO);
}
return latest;
}
#endif /* _PCACHE_INTERNAL_H */
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