Merge pull request dlbeer#12 from FreddieChopin/cache-improvements

Cache improvements

ufat.c

@@ -94,7 +94,21 @@ int ufat_cache_evict(struct ufat *uf, ufat_block_t start, ufat_block_t count)
 	return 0;
 }
 
-int ufat_cache_open(struct ufat *uf, ufat_block_t blk_index)
+void ufat_cache_invalidate(struct ufat *uf, ufat_block_t start,
+			   ufat_block_t count)
+{
+	unsigned int i;
+
+	for (i = 0; i < uf->cache_size; i++) {
+		struct ufat_cache_desc *d = &uf->cache_desc[i];
+
+		if ((d->flags & UFAT_CACHE_FLAG_PRESENT) &&
+		    d->index >= start && d->index < start + count)
+			d->flags = 0;
+	}
+}
+
+int ufat_cache_open(struct ufat *uf, ufat_block_t blk_index, int skip_read)
 {
 	unsigned int i;
 	int oldest = -1;
@@ -139,22 +153,27 @@ int ufat_cache_open(struct ufat *uf, ufat_block_t blk_index)
 		i = oldest;
 	}
 
-	/* Read it in */
-	err = uf->dev->read(uf->dev, blk_index, 1, ufat_cache_data(uf, i));
-	if (err < 0) {
-		uf->cache_desc[i].flags = 0;
-		return err;
-	} else {
-		struct ufat_cache_desc *d = &uf->cache_desc[i];
+	if (skip_read == 0) {
+		/* Read it in */
+		err = uf->dev->read(uf->dev, blk_index, 1,
+				    ufat_cache_data(uf, i));
+		if (err < 0) {
+			uf->cache_desc[i].flags = 0;
+			return err;
+		}
 
-		d->flags = UFAT_CACHE_FLAG_PRESENT;
-		d->index = blk_index;
-		d->seq = uf->next_seq++;
-	}
+		uf->stat.read++;
+		uf->stat.read_blocks++;
+	} else
+		memset(ufat_cache_data(uf, i), 0,
+		       1 << uf->dev->log2_block_size);
+
+	struct ufat_cache_desc *d = &uf->cache_desc[i];
+	d->flags = UFAT_CACHE_FLAG_PRESENT;
+	d->index = blk_index;
+	d->seq = uf->next_seq++;
 
 	uf->stat.cache_miss++;
-	uf->stat.read++;
-	uf->stat.read_blocks++;
 
 	return i;
 }
@@ -270,7 +289,7 @@ static int read_bpb(struct ufat *uf)
 {
 	int idx;
 
-	idx = ufat_cache_open(uf, 0);
+	idx = ufat_cache_open(uf, 0, 0);
 	if (idx < 0)
 		return idx;
 
@@ -382,7 +401,7 @@ static int read_fat_byte(struct ufat *uf, unsigned int offset, uint8_t *out)
 	unsigned int r = offset & ((1 << uf->dev->log2_block_size) - 1);
 	int idx;
 
-	idx = ufat_cache_open(uf, uf->bpb.fat_start + b);
+	idx = ufat_cache_open(uf, uf->bpb.fat_start + b, 0);
 	if (idx < 0)
 		return idx;
 
@@ -439,7 +458,7 @@ static int read_fat16(struct ufat *uf, ufat_cluster_t index,
 	const unsigned int shift = uf->dev->log2_block_size - 1;
 	const unsigned int b = index >> shift;
 	const unsigned int r = index & ((1 << shift) - 1);
-	int i = ufat_cache_open(uf, uf->bpb.fat_start + b);
+	int i = ufat_cache_open(uf, uf->bpb.fat_start + b, 0);
 	uint16_t raw;
 
 	if (i < 0)
@@ -467,7 +486,7 @@ static int read_fat32(struct ufat *uf, ufat_cluster_t index,
 	const unsigned int shift = uf->dev->log2_block_size - 2;
 	const unsigned int b = index >> shift;
 	const unsigned int r = index & ((1 << shift) - 1);
-	int i = ufat_cache_open(uf, uf->bpb.fat_start + b);
+	int i = ufat_cache_open(uf, uf->bpb.fat_start + b, 0);
 	uint32_t raw;
 
 	if (i < 0)
@@ -512,7 +531,7 @@ static int write_fat_byte(struct ufat *uf, unsigned int offset,
 	int idx;
 	uint8_t *data;
 
-	idx = ufat_cache_open(uf, uf->bpb.fat_start + b);
+	idx = ufat_cache_open(uf, uf->bpb.fat_start + b, 0);
 	if (idx < 0)
 		return idx;
 
@@ -552,7 +571,7 @@ static int write_fat16(struct ufat *uf, ufat_cluster_t index,
 	const unsigned int shift = uf->dev->log2_block_size - 1;
 	const unsigned int b = index >> shift;
 	const unsigned int r = index & ((1 << shift) - 1);
-	int i = ufat_cache_open(uf, uf->bpb.fat_start + b);
+	int i = ufat_cache_open(uf, uf->bpb.fat_start + b, 0);
 
 	if (i < 0)
 		return i;
@@ -569,7 +588,7 @@ static int write_fat32(struct ufat *uf, ufat_cluster_t index,
 	const unsigned int shift = uf->dev->log2_block_size - 2;
 	const unsigned int b = index >> shift;
 	const unsigned int r = index & ((1 << shift) - 1);
-	int i = ufat_cache_open(uf, uf->bpb.fat_start + b);
+	int i = ufat_cache_open(uf, uf->bpb.fat_start + b, 0);
 
 	if (i < 0)
 		return i;

ufat_dir.c

@@ -246,7 +246,7 @@ static int create_empty_dir(struct ufat_directory *parent,
 
 	/* Get the first block of the dirent */
 	idx = ufat_cache_open(parent->uf,
-			      cluster_to_block(&parent->uf->bpb, c));
+			      cluster_to_block(&parent->uf->bpb, c), 0);
 	if (idx < 0) {
 		ufat_free_chain(parent->uf, c);
 		return idx;

ufat_ent.c

@@ -45,7 +45,7 @@ int ufat_write_raw_dirent(struct ufat_directory *dir,
 	if (dir->cur_block == UFAT_BLOCK_NONE)
 		return -UFAT_ERR_IO;
 
-	idx = ufat_cache_open(dir->uf, dir->cur_block);
+	idx = ufat_cache_open(dir->uf, dir->cur_block, 0);
 	if (idx < 0)
 		return idx;
 
@@ -140,7 +140,7 @@ int ufat_read_raw_dirent(struct ufat_directory *dir, uint8_t *data)
 	if (dir->cur_block == UFAT_BLOCK_NONE)
 		return 1;
 
-	idx = ufat_cache_open(dir->uf, dir->cur_block);
+	idx = ufat_cache_open(dir->uf, dir->cur_block, 0);
 	if (idx < 0)
 		return idx;
 
@@ -210,7 +210,7 @@ int ufat_init_dirent_cluster(struct ufat *uf, ufat_cluster_t c)
 	int i;
 
 	for (i = count - 1; i >= 0; i--) {
-		int idx = ufat_cache_open(uf, start + i);
+		int idx = ufat_cache_open(uf, start + i, 1);
 
 		if (idx < 0)
 			return idx;
@@ -644,7 +644,7 @@ int ufat_compare_name(const char *search_name, const char *dir_name,
 
 int ufat_update_attributes(struct ufat *uf, struct ufat_dirent *ent)
 {
-	int idx = ufat_cache_open(uf, ent->dirent_block);
+	int idx = ufat_cache_open(uf, ent->dirent_block, 0);
 	uint8_t *data;
 	struct ufat_dirent old;
 

ufat_file.c

@@ -125,7 +125,7 @@ static int read_block_fragment(struct ufat_file *f, char *buf, ufat_size_t size)
 	if (!UFAT_CLUSTER_IS_PTR(f->cur_cluster))
 		return -UFAT_ERR_INVALID_CLUSTER;
 
-	i = ufat_cache_open(f->uf, cur_block);
+	i = ufat_cache_open(f->uf, cur_block, 0);
 	if (i < 0)
 		return i;
 
@@ -223,7 +223,7 @@ int ufat_file_read(struct ufat_file *f, void *buf, ufat_size_t size)
 
 static int set_size(struct ufat_file *f, ufat_size_t s)
 {
-	int idx = ufat_cache_open(f->uf, f->dirent_block);
+	int idx = ufat_cache_open(f->uf, f->dirent_block, 0);
 
 	if (idx < 0)
 		return idx;
@@ -238,7 +238,7 @@ static int set_size(struct ufat_file *f, ufat_size_t s)
 
 static int set_start(struct ufat_file *f, ufat_cluster_t s)
 {
-	int idx = ufat_cache_open(f->uf, f->dirent_block);
+	int idx = ufat_cache_open(f->uf, f->dirent_block, 0);
 	uint8_t *data;
 
 	if (idx < 0)
@@ -305,7 +305,7 @@ static int write_block_fragment(struct ufat_file *f, const char *buf,
 		((f->cur_pos >> log2_block_size) &
 		 ((1 << bpb->log2_blocks_per_cluster) - 1));
 
-	i = ufat_cache_open(f->uf, cur_block);
+	i = ufat_cache_open(f->uf, cur_block, 0);
 	if (i < 0)
 		return i;
 
@@ -347,9 +347,7 @@ static int write_blocks(struct ufat_file *f, const char *buf, ufat_size_t size)
 	 * cache and perform a single large write.
 	 */
 	starting_block = cluster_to_block(bpb, f->cur_cluster) + block_offset;
-	i = ufat_cache_evict(uf, starting_block, requested_blocks);
-	if (i < 0)
-		return i;
+	ufat_cache_invalidate(uf, starting_block, requested_blocks);
 
 	i = uf->dev->write(uf->dev, starting_block, requested_blocks, buf);
 	if (i < 0)

ufat_internal.h

@@ -82,9 +82,56 @@ static inline ufat_cluster_t block_to_cluster(const struct ufat_bpb *bpb,
 }
 
 /* Block IO via internal cache */
-int ufat_cache_open(struct ufat *uf, ufat_block_t blk_index);
+
+/**
+ * \brief Opens a block via cache.
+ *
+ * \pre `uf` is a valid pointer.
+ * \pre The filesystem pointed by `uf` is opened.
+ *
+ * \param [in] uf is a pointer to the filesystem
+ * \param [in] blk_index is the index of block which should be opened
+ * \param [in] skip_read selects the behavior when block is not present in the
+ * cache:
+ * - 0 - current contents of the block are read from the device;
+ * - not 0 - read operation is skipped and the cached contents are just zeroed -
+ * this is useful when the whole block is going to be overwritten anyway;
+ *
+ * \return cache index on success, negative error code (`ufat_error_t`)
+ * otherwise
+ */
+
+int ufat_cache_open(struct ufat *uf, ufat_block_t blk_index, int skip_read);
+
+/**
+ * \brief Evicts (flushes) cached blocks which overlap with given range.
+ *
+ * \pre `uf` is a valid pointer.
+ * \pre The filesystem pointed by `uf` is opened.
+ *
+ * \param [in] uf is a pointer to the filesystem
+ * \param [in] start is the index of starting block of the range
+ * \param [in] count is the number of blocks in the range
+ *
+ * \return 0 on success, negative error code (`ufat_error_t`) otherwise
+ */
+
 int ufat_cache_evict(struct ufat *uf, ufat_block_t start, ufat_block_t count);
 
+/**
+ * \brief Invalidates (drops) cached blocks which overlap with given range.
+ *
+ * \pre `uf` is a valid pointer.
+ * \pre The filesystem pointed by `uf` is opened.
+ *
+ * \param [in] uf is a pointer to the filesystem
+ * \param [in] start is the index of starting block of the range
+ * \param [in] count is the number of blocks in the range
+ */
+
+void ufat_cache_invalidate(struct ufat *uf, ufat_block_t start,
+			   ufat_block_t count);
+
 static inline void ufat_cache_write(struct ufat *uf, unsigned int cache_index)
 {
 	uf->stat.cache_write++;