[RFC][PATCH 03/10] pstore/zone: introduce directly mapped zones

[Eugen Hristev <eugen.hristev@linaro.org>]

Directly mapped zones have a different semantic from usual pstore zones.
Such zones use a pointer to data in their buffer struct, instead of
keeping the buffer locally.
The data pointer and size is then passed to the backend for further use.
Having a different semantics, backends supporting only these do not offer
read/write ops, and only new register_dmr and unregister_dmr ops.
Ofcourse, a backend could support both classic zones and directly mapped.
Directly mapped zones have the advantage of not being passed through
in the event of a crashed, but rather at registration time.

Signed-off-by: Eugen Hristev <eugen.hristev@linaro.org>
---
 fs/pstore/platform.c        |  1 +
 fs/pstore/smem.c            |  6 ++---
 fs/pstore/zone.c            | 45 ++++++++++++++++++++++++++++---------
 include/linux/pstore.h      |  4 ++++
 include/linux/pstore_zone.h |  3 +++
 5 files changed, 45 insertions(+), 14 deletions(-)

diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index f56b066ab80c..e20e60b88727 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -51,6 +51,7 @@ static const char * const pstore_type_names[] = {
 	"powerpc-common",
 	"pmsg",
 	"powerpc-opal",
+	"directly-mapped",
 };
 
 static int pstore_new_entry;
diff --git a/fs/pstore/smem.c b/fs/pstore/smem.c
index 9eedd7df5446..684ecc20cae5 100644
--- a/fs/pstore/smem.c
+++ b/fs/pstore/smem.c
@@ -36,15 +36,15 @@ static int __register_pstore_device(struct pstore_device_info *dev)
 		pr_err("NULL device info\n");
 		return -EINVAL;
 	}
-	if (!dev->zone.total_size) {
+	if (!dev->zone.total_size && !dev->zone.dmapped_cnt) {
 		pr_err("zero sized device\n");
 		return -EINVAL;
 	}
-	if (!dev->zone.read) {
+	if (!dev->zone.read && !dev->zone.dmapped_cnt) {
 		pr_err("no read handler for device\n");
 		return -EINVAL;
 	}
-	if (!dev->zone.write) {
+	if (!dev->zone.write && !dev->zone.dmapped_cnt) {
 		pr_err("no write handler for device\n");
 		return -EINVAL;
 	}
diff --git a/fs/pstore/zone.c b/fs/pstore/zone.c
index 5fa2fa2e7aa7..affa4370208c 100644
--- a/fs/pstore/zone.c
+++ b/fs/pstore/zone.c
@@ -113,6 +113,7 @@ struct psz_context {
 	struct pstore_zone *ppsz;
 	struct pstore_zone *cpsz;
 	struct pstore_zone **fpszs;
+	struct pstore_zone **dmszs;
 	unsigned int kmsg_max_cnt;
 	unsigned int kmsg_read_cnt;
 	unsigned int kmsg_write_cnt;
@@ -120,6 +121,7 @@ struct psz_context {
 	unsigned int console_read_cnt;
 	unsigned int ftrace_max_cnt;
 	unsigned int ftrace_read_cnt;
+	unsigned int dmapped_max_cnt;
 	/*
 	 * These counters should be calculated during recovery.
 	 * It records the oops/panic times after crashes rather than boots.
@@ -1148,6 +1150,8 @@ static void psz_free_all_zones(struct psz_context *cxt)
 		psz_free_zone(&cxt->cpsz);
 	if (cxt->fpszs)
 		psz_free_zones(&cxt->fpszs, &cxt->ftrace_max_cnt);
+	if (cxt->dmszs)
+		psz_free_zones(&cxt->dmszs, &cxt->dmapped_max_cnt);
 }
 
 static struct pstore_zone *psz_init_zone(enum pstore_type_id type,
@@ -1160,9 +1164,9 @@ static struct pstore_zone *psz_init_zone(enum pstore_type_id type,
 	if (!size)
 		return NULL;
 
-	if (*off + size > info->total_size) {
-		pr_err("no room for %s (0x%zx@0x%llx over 0x%lx)\n",
-			name, size, *off, info->total_size);
+	if (*off + size > info->total_size && type != PSTORE_TYPE_DMAPPED) {
+		pr_err("no room for %s type %d (0x%zx@0x%llx over 0x%lx)\n",
+			name, type, size, *off, info->total_size);
 		return ERR_PTR(-ENOMEM);
 	}
 
@@ -1170,7 +1174,8 @@ static struct pstore_zone *psz_init_zone(enum pstore_type_id type,
 	if (!zone)
 		return ERR_PTR(-ENOMEM);
 
-	zone->buffer = kmalloc(size, GFP_KERNEL);
+	zone->buffer = kmalloc(type == PSTORE_TYPE_DMAPPED ?
+			       sizeof(struct psz_buffer) : size, GFP_KERNEL);
 	if (!zone->buffer) {
 		kfree(zone);
 		return ERR_PTR(-ENOMEM);
@@ -1179,7 +1184,10 @@ static struct pstore_zone *psz_init_zone(enum pstore_type_id type,
 	zone->off = *off;
 	zone->name = name;
 	zone->type = type;
-	zone->buffer_size = size - sizeof(struct psz_buffer);
+	if (zone->type == PSTORE_TYPE_DMAPPED)
+		zone->buffer_size = 0;
+	else
+		zone->buffer_size = size - sizeof(struct psz_buffer);
 	zone->buffer->sig = type ^ PSZ_SIG;
 	zone->oldbuf = NULL;
 	atomic_set(&zone->dirty, 0);
@@ -1188,8 +1196,9 @@ static struct pstore_zone *psz_init_zone(enum pstore_type_id type,
 
 	*off += size;
 
-	pr_debug("pszone %s: off 0x%llx, %zu header, %zu data\n", zone->name,
-			zone->off, sizeof(*zone->buffer), zone->buffer_size);
+	pr_debug("pszone %s: off 0x%llx, %zu header, %zu data %s\n", zone->name,
+			zone->off, sizeof(*zone->buffer), zone->buffer_size,
+			zone->type == PSTORE_TYPE_DMAPPED ? " dmapped " : "");
 	return zone;
 }
 
@@ -1206,7 +1215,7 @@ static struct pstore_zone **psz_init_zones(enum pstore_type_id type,
 	if (!total_size || !record_size)
 		return NULL;
 
-	if (*off + total_size > info->total_size) {
+	if (*off + total_size > info->total_size && type != PSTORE_TYPE_DMAPPED) {
 		pr_err("no room for zones %s (0x%zx@0x%llx over 0x%lx)\n",
 			name, total_size, *off, info->total_size);
 		return ERR_PTR(-ENOMEM);
@@ -1245,6 +1254,15 @@ static int psz_alloc_zones(struct psz_context *cxt)
 	int err;
 	size_t off_size = 0;
 
+	cxt->dmszs = psz_init_zones(PSTORE_TYPE_DMAPPED, &off,
+			info->dmapped_cnt,
+			1, &cxt->dmapped_max_cnt);
+	if (IS_ERR(cxt->dmszs)) {
+		err = PTR_ERR(cxt->dmszs);
+		cxt->dmszs = NULL;
+		goto free_out;
+	}
+
 	off_size += info->pmsg_size;
 	cxt->ppsz = psz_init_zone(PSTORE_TYPE_PMSG, &off, info->pmsg_size);
 	if (IS_ERR(cxt->ppsz)) {
@@ -1302,7 +1320,7 @@ int register_pstore_zone(struct pstore_zone_info *info)
 	int err = -EINVAL;
 	struct psz_context *cxt = &pstore_zone_cxt;
 
-	if (info->total_size < 4096) {
+	if (info->total_size < 4096 && !info->dmapped_cnt) {
 		pr_warn("total_size must be >= 4096\n");
 		return -EINVAL;
 	}
@@ -1312,7 +1330,7 @@ int register_pstore_zone(struct pstore_zone_info *info)
 	}
 
 	if (!info->kmsg_size && !info->pmsg_size && !info->console_size &&
-	    !info->ftrace_size) {
+	    !info->ftrace_size && !info->dmapped_cnt) {
 		pr_warn("at least one record size must be non-zero\n");
 		return -EINVAL;
 	}
@@ -1345,7 +1363,7 @@ int register_pstore_zone(struct pstore_zone_info *info)
 	 * if no @read, pstore may mount failed.
 	 * if no @write, pstore do not support to remove record file.
 	 */
-	if (!info->read || !info->write) {
+	if (!info->dmapped_cnt && (!info->read || !info->write)) {
 		pr_err("no valid general read/write interface\n");
 		return -EINVAL;
 	}
@@ -1365,6 +1383,7 @@ int register_pstore_zone(struct pstore_zone_info *info)
 	pr_debug("\tpmsg size : %ld Bytes\n", info->pmsg_size);
 	pr_debug("\tconsole size : %ld Bytes\n", info->console_size);
 	pr_debug("\tftrace size : %ld Bytes\n", info->ftrace_size);
+	pr_debug("\tdmapped areas : %ld\n", info->dmapped_cnt);
 
 	err = psz_alloc_zones(cxt);
 	if (err) {
@@ -1406,6 +1425,10 @@ int register_pstore_zone(struct pstore_zone_info *info)
 		cxt->pstore.flags |= PSTORE_FLAGS_FTRACE;
 		pr_cont(" ftrace");
 	}
+	if (info->dmapped_cnt) {
+		cxt->pstore.flags |= PSTORE_FLAGS_DMAPPED;
+		pr_cont(" dmapped");
+	}
 	pr_cont("\n");
 
 	err = pstore_register(&cxt->pstore);
diff --git a/include/linux/pstore.h b/include/linux/pstore.h
index fed601053c51..8360d94c96b6 100644
--- a/include/linux/pstore.h
+++ b/include/linux/pstore.h
@@ -39,6 +39,7 @@ enum pstore_type_id {
 	PSTORE_TYPE_PMSG	= 7,
 	PSTORE_TYPE_PPC_OPAL	= 8,
 
+	PSTORE_TYPE_DMAPPED	= 9,
 	/* End of the list */
 	PSTORE_TYPE_MAX
 };
@@ -199,6 +200,8 @@ struct pstore_info {
 	int		(*write_user)(struct pstore_record *record,
 				      const char __user *buf);
 	int		(*erase)(struct pstore_record *record);
+	int		(*register_dmr)(struct pstore_record *record);
+	int		(*unregister_dmr)(struct pstore_record *record);
 };
 
 /* Supported frontends */
@@ -206,6 +209,7 @@ struct pstore_info {
 #define PSTORE_FLAGS_CONSOLE	BIT(1)
 #define PSTORE_FLAGS_FTRACE	BIT(2)
 #define PSTORE_FLAGS_PMSG	BIT(3)
+#define PSTORE_FLAGS_DMAPPED	BIT(4)
 
 extern int pstore_register(struct pstore_info *);
 extern void pstore_unregister(struct pstore_info *);
diff --git a/include/linux/pstore_zone.h b/include/linux/pstore_zone.h
index 284364234162..a74d0cc75577 100644
--- a/include/linux/pstore_zone.h
+++ b/include/linux/pstore_zone.h
@@ -48,10 +48,13 @@ struct pstore_zone_info {
 	unsigned long pmsg_size;
 	unsigned long console_size;
 	unsigned long ftrace_size;
+	unsigned long dmapped_cnt;
 	pstore_zone_read_op read;
 	pstore_zone_write_op write;
 	pstore_zone_erase_op erase;
 	pstore_zone_write_op panic_write;
+	int (*register_dmr)(char *, int, void *, size_t);
+	int (*unregister_dmr)(void *, size_t);
 };
 
 /**
-- 
2.43.0