[PATCH v2 2/3] part: efi: add GPT PTE cache used with part_get_info_cached() API
Heinrich Schuchardt
xypron.glpk at gmx.de
Tue Apr 8 12:57:50 CEST 2025
On 08.04.25 11:13, Neil Armstrong wrote:
> Implement a simple cache for part_efi to be used by the newly
> introduced part_get_info_cached() API.
>
> The cache simply stores a successfully scanned GPT PTE if called
> from the part_get_info_cached() ops, and will return the cached
> data if the blk_desc and lba offset matches, invalidating the
> cache if not.
>
> The cache will only operate if called from the part_get_info_cached()
> API, all the over calls will operate uncached, making sure we
> can still update & re-scan the GPT partitions like before.
>
> Signed-off-by: Neil Armstrong <neil.armstrong at linaro.org>
> ---
> disk/part_efi.c | 114 +++++++++++++++++++++++++++++++++++++++++++++++---------
> 1 file changed, 96 insertions(+), 18 deletions(-)
>
> diff --git a/disk/part_efi.c b/disk/part_efi.c
> index 932d058c184ce6946b7142e7c2d9637b28e4661e..949968fcd30fc18766a023e73f43ca1381dcef89 100644
> --- a/disk/part_efi.c
> +++ b/disk/part_efi.c
> @@ -55,12 +55,58 @@ static inline u32 efi_crc32(const void *buf, u32 len)
> static int pmbr_part_valid(struct partition *part);
> static int is_pmbr_valid(legacy_mbr * mbr);
> static int is_gpt_valid(struct blk_desc *desc, u64 lba, gpt_header *pgpt_head,
> - gpt_entry **pgpt_pte);
> + gpt_entry **pgpt_pte, bool cache);
> static gpt_entry *alloc_read_gpt_entries(struct blk_desc *desc,
> gpt_header *pgpt_head);
> static int is_pte_valid(gpt_entry * pte);
> static int find_valid_gpt(struct blk_desc *desc, gpt_header *gpt_head,
> - gpt_entry **pgpt_pte);
> + gpt_entry **pgpt_pte, bool cache);
> +
Please, describe the structure and its members.
https://docs.kernel.org/doc-guide/kernel-doc.html#structure-union-and-enumeration-documentation
> +static struct gpt_pte_cache_data {
> + struct blk_desc *desc;
> + u64 lba;
> + gpt_entry *gpt_pte;
> + gpt_header gpt_head;
> +} gpt_pte_cache;
> +
Please, describe all functions.
> +static void clear_gpt_pte_cache(void)
> +{
> + if (gpt_pte_cache.desc) {
> + if (gpt_pte_cache.gpt_pte)
> + free(gpt_pte_cache.gpt_pte);
> +
> + memset(&gpt_pte_cache, 0, sizeof(gpt_pte_cache));
> + }
> +}
> +
> +static void cache_gpt_pte(struct blk_desc *desc, u64 lba,
> + gpt_entry *gpt_pte, gpt_header *pgpt_head)
> +{
> + if (gpt_pte_cache.gpt_pte)
> + free(gpt_pte_cache.gpt_pte);
> +
> + gpt_pte_cache.desc = desc;
> + gpt_pte_cache.lba = lba;
> + gpt_pte_cache.gpt_pte = gpt_pte;
> + if (pgpt_head)
> + memcpy(&gpt_pte_cache.gpt_head, pgpt_head, sizeof(gpt_header));
> +}
> +
> +static gpt_entry *get_cached_gpt_pte(struct blk_desc *desc, u64 lba,
> + gpt_header *pgpt_head)
> +{
> + if (gpt_pte_cache.desc && gpt_pte_cache.gpt_pte) {
> + if (gpt_pte_cache.desc == desc &&
> + gpt_pte_cache.lba == lba) {
> + memcpy(pgpt_head, &gpt_pte_cache.gpt_head, sizeof(gpt_header));
> + return gpt_pte_cache.gpt_pte;
> + }
> +
> + clear_gpt_pte_cache();
> + }
> +
> + return NULL;
> +}
>
> static char *print_efiname(gpt_entry *pte)
> {
> @@ -205,7 +251,7 @@ int get_disk_guid(struct blk_desc *desc, char *guid)
> unsigned char *guid_bin;
>
> /* This function validates AND fills in the GPT header and PTE */
> - if (find_valid_gpt(desc, gpt_head, &gpt_pte) != 1)
> + if (find_valid_gpt(desc, gpt_head, &gpt_pte, false) != 1)
> return -EINVAL;
>
> guid_bin = gpt_head->disk_guid.b;
> @@ -224,7 +270,7 @@ static void __maybe_unused part_print_efi(struct blk_desc *desc)
> unsigned char *uuid;
>
> /* This function validates AND fills in the GPT header and PTE */
> - if (find_valid_gpt(desc, gpt_head, &gpt_pte) != 1)
> + if (find_valid_gpt(desc, gpt_head, &gpt_pte, false) != 1)
> return;
>
> debug("%s: gpt-entry at %p\n", __func__, gpt_pte);
> @@ -258,8 +304,13 @@ static void __maybe_unused part_print_efi(struct blk_desc *desc)
> return;
> }
>
> -static int __maybe_unused part_get_info_efi(struct blk_desc *desc, int part,
> - struct disk_partition *info)
> +static void __maybe_unused part_get_info_cache_free_efi(struct blk_desc *desc)
> +{
> + clear_gpt_pte_cache();
> +}
> +
> +static int _part_get_info_efi(struct blk_desc *desc, int part,
> + struct disk_partition *info, bool cache)
> {
> ALLOC_CACHE_ALIGN_BUFFER_PAD(gpt_header, gpt_head, 1, desc->blksz);
> gpt_entry *gpt_pte = NULL;
> @@ -271,13 +322,14 @@ static int __maybe_unused part_get_info_efi(struct blk_desc *desc, int part,
> }
>
> /* This function validates AND fills in the GPT header and PTE */
> - if (find_valid_gpt(desc, gpt_head, &gpt_pte) != 1)
> + if (find_valid_gpt(desc, gpt_head, &gpt_pte, cache) != 1)
> return -EINVAL;
>
> if (part > le32_to_cpu(gpt_head->num_partition_entries) ||
> !is_pte_valid(&gpt_pte[part - 1])) {
> log_debug("Invalid partition number %d\n", part);
> - free(gpt_pte);
> + if (!cache)
> + free(gpt_pte);
> return -EPERM;
> }
>
> @@ -307,11 +359,23 @@ static int __maybe_unused part_get_info_efi(struct blk_desc *desc, int part,
> log_debug("start 0x" LBAF ", size 0x" LBAF ", name %s\n", info->start,
> info->size, info->name);
>
> - /* Remember to free pte */
> - free(gpt_pte);
> + if (!cache)
> + free(gpt_pte);
> return 0;
> }
>
> +static int __maybe_unused part_get_info_cached_efi(struct blk_desc *desc, int part,
> + struct disk_partition *info)
> +{
> + return _part_get_info_efi(desc, part, info, true);
> +}
> +
> +static int __maybe_unused part_get_info_efi(struct blk_desc *desc, int part,
> + struct disk_partition *info)
> +{
> + return _part_get_info_efi(desc, part, info, false);
> +}
> +
> static int part_test_efi(struct blk_desc *desc)
> {
> ALLOC_CACHE_ALIGN_BUFFER_PAD(legacy_mbr, legacymbr, 1, desc->blksz);
> @@ -689,7 +753,7 @@ int gpt_verify_headers(struct blk_desc *desc, gpt_header *gpt_head,
> */
> if (is_gpt_valid(desc,
> GPT_PRIMARY_PARTITION_TABLE_LBA,
> - gpt_head, gpt_pte) != 1) {
> + gpt_head, gpt_pte, false) != 1) {
> log_debug("Invalid GPT\n");
> return -1;
> }
> @@ -706,7 +770,7 @@ int gpt_verify_headers(struct blk_desc *desc, gpt_header *gpt_head,
> }
>
> if (is_gpt_valid(desc, (desc->lba - 1),
> - gpt_head, gpt_pte) != 1) {
> + gpt_head, gpt_pte, false) != 1) {
> log_debug("Invalid Backup GPT\n");
> return -1;
> }
> @@ -765,9 +829,9 @@ int gpt_repair_headers(struct blk_desc *desc)
> int ret = -1;
>
> is_gpt1_valid = is_gpt_valid(desc, GPT_PRIMARY_PARTITION_TABLE_LBA,
> - gpt_h1, &gpt_e1);
> + gpt_h1, &gpt_e1, false);
> is_gpt2_valid = is_gpt_valid(desc, desc->lba - 1,
> - gpt_h2, &gpt_e2);
> + gpt_h2, &gpt_e2, false);
>
> if (is_gpt1_valid && is_gpt2_valid) {
> ret = 0;
> @@ -1023,12 +1087,13 @@ static int is_pmbr_valid(legacy_mbr *mbr)
> * lba is the logical block address of the GPT header to test
> * gpt is a GPT header ptr, filled on return.
> * ptes is a PTEs ptr, filled on return.
> + * cache is a bool, true to use the cached gpt_pte from previous call
"use the cache" or "use cached GPT if available"?
It remains unclear what will happen if cache=1 and no entry is found.
Best regards
Heinrich
> *
> * Description: returns 1 if valid, 0 on error, 2 if ignored header
> * If valid, returns pointers to PTEs.
> */
> static int is_gpt_valid(struct blk_desc *desc, u64 lba, gpt_header *pgpt_head,
> - gpt_entry **pgpt_pte)
> + gpt_entry **pgpt_pte, bool cache)
> {
> /* Confirm valid arguments prior to allocation. */
> if (!desc || !pgpt_head) {
> @@ -1036,6 +1101,12 @@ static int is_gpt_valid(struct blk_desc *desc, u64 lba, gpt_header *pgpt_head,
> return 0;
> }
>
> + if (cache) {
> + *pgpt_pte = get_cached_gpt_pte(desc, lba, pgpt_head);
> + if (*pgpt_pte)
> + return 1;
> + }
> +
> ALLOC_CACHE_ALIGN_BUFFER_PAD(legacy_mbr, mbr, 1, desc->blksz);
>
> /* Read MBR Header from device */
> @@ -1081,6 +1152,9 @@ static int is_gpt_valid(struct blk_desc *desc, u64 lba, gpt_header *pgpt_head,
> return 0;
> }
>
> + if (cache)
> + cache_gpt_pte(desc, lba, *pgpt_pte, pgpt_head);
> +
> /* We're done, all's well */
> return 1;
> }
> @@ -1090,23 +1164,25 @@ static int is_gpt_valid(struct blk_desc *desc, u64 lba, gpt_header *pgpt_head,
> *
> * gpt is a GPT header ptr, filled on return.
> * ptes is a PTEs ptr, filled on return.
> + * cache if a bool, use cached GPT if available
> *
> * Description: returns 1 if found a valid gpt, 0 on error.
> * If valid, returns pointers to PTEs.
> */
> static int find_valid_gpt(struct blk_desc *desc, gpt_header *gpt_head,
> - gpt_entry **pgpt_pte)
> + gpt_entry **pgpt_pte, bool cache)
> {
> int r;
>
> r = is_gpt_valid(desc, GPT_PRIMARY_PARTITION_TABLE_LBA, gpt_head,
> - pgpt_pte);
> + pgpt_pte, cache);
>
> if (r != 1) {
> if (r != 2)
> log_debug("Invalid GPT\n");
>
> - if (is_gpt_valid(desc, desc->lba - 1, gpt_head, pgpt_pte)
> + if (is_gpt_valid(desc, desc->lba - 1, gpt_head, pgpt_pte,
> + true)
> != 1) {
> log_debug("Invalid Backup GPT\n");
> return 0;
> @@ -1210,6 +1286,8 @@ U_BOOT_PART_TYPE(a_efi) = {
> .name = "EFI",
> .part_type = PART_TYPE_EFI,
> .max_entries = GPT_ENTRY_NUMBERS,
> + .get_info_cache_free = part_get_info_ptr(part_get_info_cache_free_efi),
> + .get_info_cached = part_get_info_ptr(part_get_info_cached_efi),
> .get_info = part_get_info_ptr(part_get_info_efi),
> .print = part_print_ptr(part_print_efi),
> .test = part_test_efi,
>
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