[U-Boot] [PATCH] ext4: cache first extent index blocks (#06343)

Christophe Ronco c.ronco at kerlink.fr
Fri Oct 27 14:18:11 UTC 2017


Extent index blocks are read many times when reading completely a big file.
This is time costly if underlying driver is slow.
Caching the first index blocks cost a bit of RAM but speed up file reading a lot.
---
 fs/ext4/ext4_common.c | 93 ++++++++++++++++++++++++++++++++++++++++++++++++---
 fs/ext4/ext4_common.h | 16 +++++++++
 fs/ext4/ext4fs.c      | 16 +++++++--
 3 files changed, 117 insertions(+), 8 deletions(-)

diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c
index cab5465..68ab2e9 100644
--- a/fs/ext4/ext4_common.c
+++ b/fs/ext4/ext4_common.c
@@ -44,6 +44,7 @@ int ext4fs_indir3_size;
 int ext4fs_indir3_blkno = -1;
 struct ext2_inode *g_parent_inode;
 static int symlinknest;
+struct ext4_extent_blocs ext4fs_extents_blocs;
 
 #if defined(CONFIG_EXT4_WRITE)
 uint32_t ext4fs_div_roundup(uint32_t size, uint32_t n)
@@ -1413,6 +1414,7 @@ static struct ext4_extent_header *ext4fs_get_extent_block
 	unsigned long long block;
 	int blksz = EXT2_BLOCK_SIZE(data);
 	int i;
+	int found;
 
 	while (1) {
 		index = (struct ext4_extent_idx *)(ext_block + 1);
@@ -1435,11 +1437,24 @@ static struct ext4_extent_header *ext4fs_get_extent_block
 		block = le16_to_cpu(index[i].ei_leaf_hi);
 		block = (block << 32) + le32_to_cpu(index[i].ei_leaf_lo);
 
-		if (ext4fs_devread((lbaint_t)block << log2_blksz, 0, blksz,
-				   buf))
-			ext_block = (struct ext4_extent_header *)buf;
-		else
-			return 0;
+		/* look in saved extent blocks */
+		found = 0;
+		for (i = 0; i < ext4fs_extents_blocs.bloc_nb; i++) {
+			if (ext4fs_extents_blocs.ext_blocs[i].block == block) {
+				memcpy(buf, ext4fs_extents_blocs.ext_blocs[i].ext_header,
+				       blksz);
+				ext_block = (struct ext4_extent_header *)buf;
+				found = 1;
+			}
+		}
+
+		if (found == 0) {
+			if (ext4fs_devread((lbaint_t)block << log2_blksz, 0,
+					   blksz, buf))
+				ext_block = (struct ext4_extent_header *)buf;
+			else
+				return 0;
+		}
 	}
 }
 
@@ -1465,6 +1480,74 @@ static int ext4fs_blockgroup
 			      (char *)blkgrp);
 }
 
+void ext4fs_init_extents_blocks_global(void)
+{
+	memset(&ext4fs_extents_blocs, 0, sizeof(struct ext4_extent_blocs));
+}
+
+int ext4fs_read_extents_blocks(struct ext2_inode *inode)
+{
+	int blksz = EXT2_BLOCK_SIZE(ext4fs_root);
+	int log2_blksz;
+	struct ext4_extent_header *ext_block;
+	struct ext4_extent_idx *index;
+	unsigned long long block;
+	int entries;
+	char *buf;
+	int i;
+
+	ext4fs_extents_blocs.bloc_nb = 0;
+	log2_blksz = LOG2_BLOCK_SIZE(ext4fs_root)
+		- get_fs()->dev_desc->log2blksz;
+
+	if ((le32_to_cpu(inode->flags) & EXT4_EXTENTS_FL) == 0)
+		return 0;
+
+	ext_block = (struct ext4_extent_header *)inode->b.blocks.dir_blocks;
+
+	if (le16_to_cpu(ext_block->eh_magic) != EXT4_EXT_MAGIC)
+		return 0;
+	if (ext_block->eh_depth == 0)
+		return 0;
+
+	entries = le16_to_cpu(ext_block->eh_entries);
+	index = (struct ext4_extent_idx *)(ext_block + 1);
+
+	for (i = 0; (i < entries) && (i < MAX_EXTENT_BLOCS); i++) {
+		/* bloc number */
+		block = le16_to_cpu(index[i].ei_leaf_hi);
+		block = (block << 32) + le32_to_cpu(index[i].ei_leaf_lo);
+		/* bloc data */
+		buf = zalloc(blksz);
+		if (!buf)
+			break;
+		if (ext4fs_devread((lbaint_t)block << log2_blksz, 0, blksz,
+				   buf) == 0) {
+			free(buf);
+			break;
+		}
+		ext4fs_extents_blocs.ext_blocs[i].block = block;
+		ext4fs_extents_blocs.ext_blocs[i].ext_header =
+					(struct ext4_extent_header *)buf;
+	}
+	ext4fs_extents_blocs.bloc_nb = i;
+	return i;
+}
+
+void ext4fs_free_extents_blocks(void)
+{
+	int i;
+
+	for (i = 0; i < ext4fs_extents_blocs.bloc_nb; i++) {
+		if (ext4fs_extents_blocs.ext_blocs[i].ext_header) {
+			free(ext4fs_extents_blocs.ext_blocs[i].ext_header);
+			ext4fs_extents_blocs.ext_blocs[i].ext_header = NULL;
+			ext4fs_extents_blocs.ext_blocs[i].block = 0;
+		}
+	}
+	ext4fs_extents_blocs.bloc_nb = 0;
+}
+
 int ext4fs_read_inode(struct ext2_data *data, int ino, struct ext2_inode *inode)
 {
 	struct ext2_block_group blkgrp;
diff --git a/fs/ext4/ext4_common.h b/fs/ext4/ext4_common.h
index 48fd2ac..0f80856 100644
--- a/fs/ext4/ext4_common.h
+++ b/fs/ext4/ext4_common.h
@@ -41,6 +41,18 @@
 #define SUPERBLOCK_SIZE	1024
 #define F_FILE			1
 
+#define MAX_EXTENT_BLOCS 10
+
+struct ext4_extent_bloc {
+	unsigned long long block;
+	struct ext4_extent_header *ext_header;
+};
+
+struct ext4_extent_blocs {
+	int bloc_nb;
+	struct ext4_extent_bloc ext_blocs[MAX_EXTENT_BLOCS];
+};
+
 static inline void *zalloc(size_t size)
 {
 	void *p = memalign(ARCH_DMA_MINALIGN, size);
@@ -57,6 +69,10 @@ int ext4fs_find_file(const char *path, struct ext2fs_node *rootnode,
 int ext4fs_iterate_dir(struct ext2fs_node *dir, char *name,
 			struct ext2fs_node **fnode, int *ftype);
 
+void ext4fs_init_extents_blocks_global(void);
+int ext4fs_read_extents_blocks(struct ext2_inode *inode);
+void ext4fs_free_extents_blocks(void);
+
 #if defined(CONFIG_EXT4_WRITE)
 uint32_t ext4fs_div_roundup(uint32_t size, uint32_t n);
 int ext4fs_checksum_update(unsigned int i);
diff --git a/fs/ext4/ext4fs.c b/fs/ext4/ext4fs.c
index 258b937..88db1fb 100644
--- a/fs/ext4/ext4fs.c
+++ b/fs/ext4/ext4fs.c
@@ -70,6 +70,12 @@ int ext4fs_read_file(struct ext2fs_node *node, loff_t pos,
 
 	blockcnt = lldiv(((len + pos) + blocksize - 1), blocksize);
 
+	ext4fs_init_extents_blocks_global();
+	if (blockcnt > 100) {
+		/* Big reading: read extent blocks tree if any */
+		ext4fs_read_extents_blocks(&(node->inode));
+	}
+
 	for (i = lldiv(pos, blocksize); i < blockcnt; i++) {
 		lbaint_t blknr;
 		int blockoff = pos - (blocksize * i);
@@ -77,7 +83,7 @@ int ext4fs_read_file(struct ext2fs_node *node, loff_t pos,
 		int skipfirst = 0;
 		blknr = read_allocated_block(&(node->inode), i);
 		if (blknr < 0)
-			return -1;
+			goto error;
 
 		blknr = blknr << log2_fs_blocksize;
 
@@ -134,7 +140,7 @@ int ext4fs_read_file(struct ext2fs_node *node, loff_t pos,
 							delayed_extent,
 							delayed_buf);
 				if (status == 0)
-					return -1;
+					goto error;
 				previous_block_number = -1;
 			}
 			memset(buf, 0, blocksize - skipfirst);
@@ -147,12 +153,16 @@ int ext4fs_read_file(struct ext2fs_node *node, loff_t pos,
 					delayed_skipfirst, delayed_extent,
 					delayed_buf);
 		if (status == 0)
-			return -1;
+			goto error;
 		previous_block_number = -1;
 	}
 
 	*actread  = len;
+	ext4fs_free_extents_blocks();
 	return 0;
+error:
+	ext4fs_free_extents_blocks();
+	return -1;
 }
 
 int ext4fs_ls(const char *dirname)
-- 
2.7.4



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