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Commit 808d0387 authored by Colin Cross's avatar Colin Cross Committed by Greg Kroah-Hartman
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staging: android: persistent_ram: make persistent_ram_write atomic 



Allow persistent_ram_write to be called on multiple cpus at
the same time, as long as ecc is not in use.  Uses atomics
for the buffer->start and buffer->size counters.

[jstultz: Fix up some pr_info casting issues on 64bit]
CC: Greg KH <gregkh@linuxfoundation.org>
CC: Android Kernel Team <kernel-team@android.com>
Signed-off-by: default avatarColin Cross <ccross@android.com>
Signed-off-by: default avatarJohn Stultz <john.stultz@linaro.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 404a6043

drivers/staging/android/persistent_ram.c

+101 −39
Original line number Diff line number Diff line
@@ -27,8 +27,8 @@ 


struct persistent_ram_buffer {

	uint32_t    sig;

	uint32_t    start;

	uint32_t    size;

	atomic_t    start;

	atomic_t    size;

	uint8_t     data[0];

};
@@ -36,6 +36,66 @@ struct persistent_ram_buffer { 


static __initdata LIST_HEAD(persistent_ram_list);



static inline size_t buffer_size(struct persistent_ram_zone *prz)

{

	return atomic_read(&prz->buffer->size);

}



static inline size_t buffer_start(struct persistent_ram_zone *prz)

{

	return atomic_read(&prz->buffer->start);

}



/* increase and wrap the start pointer, returning the old value */

static inline size_t buffer_start_add(struct persistent_ram_zone *prz, size_t a)

{

	int old;

	int new;



	do {

		old = atomic_read(&prz->buffer->start);

		new = old + a;

		while (unlikely(new > prz->buffer_size))

			new -= prz->buffer_size;

	} while (atomic_cmpxchg(&prz->buffer->start, old, new) != old);



	return old;

}



/* increase the size counter until it hits the max size */

static inline void buffer_size_add(struct persistent_ram_zone *prz, size_t a)

{

	size_t old;

	size_t new;



	if (atomic_read(&prz->buffer->size) == prz->buffer_size)

		return;



	do {

		old = atomic_read(&prz->buffer->size);

		new = old + a;

		if (new > prz->buffer_size)

			new = prz->buffer_size;

	} while (atomic_cmpxchg(&prz->buffer->size, old, new) != old);

}



/* increase the size counter, retuning an error if it hits the max size */

static inline ssize_t buffer_size_add_clamp(struct persistent_ram_zone *prz,

	size_t a)

{

	size_t old;

	size_t new;



	do {

		old = atomic_read(&prz->buffer->size);

		new = old + a;

		if (new > prz->buffer_size)

			return -ENOMEM;

	} while (atomic_cmpxchg(&prz->buffer->size, old, new) != old);



	return 0;

}



static void persistent_ram_encode_rs8(struct persistent_ram_zone *prz,

	uint8_t *data, size_t len, uint8_t *ecc)

{
@@ -62,7 +122,7 @@ static int persistent_ram_decode_rs8(struct persistent_ram_zone *prz, 
}



static void persistent_ram_update_ecc(struct persistent_ram_zone *prz,

	unsigned int count)

	unsigned int start, unsigned int count)

{

	struct persistent_ram_buffer *buffer = prz->buffer;

	uint8_t *buffer_end = buffer->data + prz->buffer_size;
@@ -75,16 +135,16 @@ static void persistent_ram_update_ecc(struct persistent_ram_zone *prz, 
	if (!prz->ecc)

		return;



	block = buffer->data + (buffer->start & ~(ecc_block_size - 1));

	par = prz->par_buffer +

	      (buffer->start / ecc_block_size) * prz->ecc_size;

	block = buffer->data + (start & ~(ecc_block_size - 1));

	par = prz->par_buffer + (start / ecc_block_size) * prz->ecc_size;



	do {

		if (block + ecc_block_size > buffer_end)

			size = buffer_end - block;

		persistent_ram_encode_rs8(prz, block, size, par);

		block += ecc_block_size;

		par += ecc_size;

	} while (block < buffer->data + buffer->start + count);

	} while (block < buffer->data + start + count);

}



static void persistent_ram_update_header_ecc(struct persistent_ram_zone *prz)
@@ -109,7 +169,7 @@ static void persistent_ram_ecc_old(struct persistent_ram_zone *prz) 


	block = buffer->data;

	par = prz->par_buffer;

	while (block < buffer->data + buffer->size) {

	while (block < buffer->data + buffer_size(prz)) {

		int numerr;

		int size = prz->ecc_block_size;

		if (block + size > buffer->data + prz->buffer_size)
@@ -199,34 +259,33 @@ ssize_t persistent_ram_ecc_string(struct persistent_ram_zone *prz, 
}



static void persistent_ram_update(struct persistent_ram_zone *prz,

	const void *s, unsigned int count)

	const void *s, unsigned int start, unsigned int count)

{

	struct persistent_ram_buffer *buffer = prz->buffer;

	memcpy(buffer->data + buffer->start, s, count);

	persistent_ram_update_ecc(prz, count);

	memcpy(buffer->data + start, s, count);

	persistent_ram_update_ecc(prz, start, count);

}



static void __init

persistent_ram_save_old(struct persistent_ram_zone *prz)

{

	struct persistent_ram_buffer *buffer = prz->buffer;

	size_t old_log_size = buffer->size;

	size_t size = buffer_size(prz);

	size_t start = buffer_start(prz);

	char *dest;



	persistent_ram_ecc_old(prz);



	dest = kmalloc(old_log_size, GFP_KERNEL);

	dest = kmalloc(size, GFP_KERNEL);

	if (dest == NULL) {

		pr_err("persistent_ram: failed to allocate buffer\n");

		return;

	}



	prz->old_log = dest;

	prz->old_log_size = old_log_size;

	memcpy(prz->old_log,

	       &buffer->data[buffer->start], buffer->size - buffer->start);

	memcpy(prz->old_log + buffer->size - buffer->start,

	       &buffer->data[0], buffer->start);

	prz->old_log_size = size;

	memcpy(prz->old_log, &buffer->data[start], size - start);

	memcpy(prz->old_log + size - start, &buffer->data[0], start);

}



int persistent_ram_write(struct persistent_ram_zone *prz,
@@ -234,25 +293,26 @@ int persistent_ram_write(struct persistent_ram_zone *prz, 
{

	int rem;

	int c = count;

	struct persistent_ram_buffer *buffer = prz->buffer;

	size_t start;



	if (c > prz->buffer_size) {

	if (unlikely(c > prz->buffer_size)) {

		s += c - prz->buffer_size;

		c = prz->buffer_size;

	}

	rem = prz->buffer_size - buffer->start;

	if (rem < c) {

		persistent_ram_update(prz, s, rem);



	buffer_size_add_clamp(prz, c);



	start = buffer_start_add(prz, c);



	rem = prz->buffer_size - start;

	if (unlikely(rem < c)) {

		persistent_ram_update(prz, s, start, rem);

		s += rem;

		c -= rem;

		buffer->start = 0;

		buffer->size = prz->buffer_size;

		start = 0;

	}

	persistent_ram_update(prz, s, c);

	persistent_ram_update(prz, s, start, c);



	buffer->start += c;

	if (buffer->size < prz->buffer_size)

		buffer->size += c;

	persistent_ram_update_header_ecc(prz);



	return count;
@@ -361,23 +421,25 @@ struct persistent_ram_zone *__persistent_ram_init(struct device *dev, bool ecc) 
		return ERR_PTR(ret);



	if (prz->buffer->sig == PERSISTENT_RAM_SIG) {

		if (prz->buffer->size > prz->buffer_size

		    || prz->buffer->start > prz->buffer->size)

			pr_info("persistent_ram: found existing invalid buffer, size %d, start %d\n",

			       prz->buffer->size, prz->buffer->start);

		if (buffer_size(prz) > prz->buffer_size ||

		    buffer_start(prz) > buffer_size(prz))

			pr_info("persistent_ram: found existing invalid buffer,"

				" size %ld, start %ld\n",

			       buffer_size(prz), buffer_start(prz));

		else {

			pr_info("persistent_ram: found existing buffer, size %d, start %d\n",

			       prz->buffer->size, prz->buffer->start);

			pr_info("persistent_ram: found existing buffer,"

				" size %ld, start %ld\n",

			       buffer_size(prz), buffer_start(prz));

			persistent_ram_save_old(prz);

		}

	} else {

		pr_info("persistent_ram: no valid data in buffer (sig = 0x%08x)\n",

			prz->buffer->sig);

		pr_info("persistent_ram: no valid data in buffer"

			" (sig = 0x%08x)\n", prz->buffer->sig);

	}



	prz->buffer->sig = PERSISTENT_RAM_SIG;

	prz->buffer->start = 0;

	prz->buffer->size = 0;

	atomic_set(&prz->buffer->start, 0);

	atomic_set(&prz->buffer->size, 0);



	return prz;

}