Message-Id: <1349795401-6497-1-git-send-email-linkinjeon@gmail.com>
Date:	Wed, 10 Oct 2012 00:10:01 +0900
From:	Namjae Jeon <linkinjeon@...il.com>
To:	jack@...e.cz
Cc:	linux-kernel@...r.kernel.org, Namjae Jeon <linkinjeon@...il.com>,
	Namjae Jeon <namjae.jeon@...sung.com>,
	Ashish Sangwan <a.sangwan@...sung.com>,
	Bonggil Bak <bgbak@...sung.com>
Subject: [PATCH 5/6] udf: implement extent caching while reading-writing to a file

From: Namjae Jeon <namjae.jeon@...sung.com>

This patch implements extent caching.
Instead of reading metadata everytime from file's starting position,
now we read from the cached extent.
This speeds up the transformation of file logical offsets to
corresponding on-disk blocks.

Signed-off-by: Namjae Jeon <namjae.jeon@...sung.com>
Signed-off-by: Ashish Sangwan <a.sangwan@...sung.com>
Signed-off-by: Bonggil Bak <bgbak@...sung.com>
---
 fs/udf/ialloc.c  |    2 +
 fs/udf/inode.c   |  147 +++++++++++++++++++++++++++++++++++++++++++++++++-----
 fs/udf/udf_i.h   |   17 +++++++
 fs/udf/udfdecl.h |   10 ++--
 4 files changed, 159 insertions(+), 17 deletions(-)

diff --git a/fs/udf/ialloc.c b/fs/udf/ialloc.c
index 7e5aae4..7dd86a4a 100644
--- a/fs/udf/ialloc.c
+++ b/fs/udf/ialloc.c
@@ -117,6 +117,8 @@ struct inode *udf_new_inode(struct inode *dir, umode_t mode, int *err)
 	iinfo->i_lenAlloc = 0;
 	iinfo->i_use = 0;
 	iinfo->i_checkpoint = 1;
+	memset(&iinfo->cached_extent, 0, sizeof(struct udf_ext_cache));
+	mutex_init(&(iinfo->i_extent_cache_lock));
 	if (UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_USE_AD_IN_ICB))
 		iinfo->i_alloc_type = ICBTAG_FLAG_AD_IN_ICB;
 	else if (UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_USE_SHORT_AD))
diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 6fd9dc5..38aee74 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -90,6 +90,7 @@ void udf_evict_inode(struct inode *inode)
 	}
 	kfree(iinfo->i_ext.i_data);
 	iinfo->i_ext.i_data = NULL;
+	udf_clear_extent_cache(iinfo);
 	if (want_delete) {
 		udf_free_inode(inode);
 	}
@@ -105,6 +106,7 @@ static void udf_write_failed(struct address_space *mapping, loff_t to)
 		truncate_pagecache(inode, to, isize);
 		if (iinfo->i_alloc_type != ICBTAG_FLAG_AD_IN_ICB) {
 			down_write(&iinfo->i_data_sem);
+			udf_clear_extent_cache(iinfo);
 			udf_truncate_extents(inode);
 			up_write(&iinfo->i_data_sem);
 		}
@@ -588,27 +590,32 @@ static sector_t inode_getblk(struct inode *inode, sector_t block,
 			     int *err, int *new)
 {
 	struct kernel_long_ad laarr[EXTENT_MERGE_SIZE];
-	struct extent_position prev_epos, cur_epos, next_epos;
-	int count = 0, startnum = 0, endnum = 0;
+	struct extent_position prev_epos, cur_epos, next_epos, cache_epos;
+	int count = 0, startnum = 0, endnum = 0, epos_count;
 	uint32_t elen = 0, tmpelen;
 	struct kernel_lb_addr eloc, tmpeloc;
 	int c = 1;
 	loff_t lbcount = 0, b_off = 0;
+	loff_t cur_ext_lbcount = 0, prev_ext_lbcount = 0;
 	uint32_t newblocknum, newblock;
 	sector_t offset = 0;
 	int8_t etype;
 	struct udf_inode_info *iinfo = UDF_I(inode);
 	int goal = 0, pgoal = iinfo->i_location.logicalBlockNum;
-	int lastblock = 0;
+	int lastblock = 0, check_endnum = 0;
 	bool isBeyondEOF;
 
 	*err = 0;
 	*new = 0;
-	prev_epos.offset = udf_file_entry_alloc_offset(inode);
-	prev_epos.block = iinfo->i_location;
-	prev_epos.bh = NULL;
-	cur_epos = next_epos = prev_epos;
 	b_off = (loff_t)block << inode->i_sb->s_blocksize_bits;
+	if (!udf_read_extent_cache(inode, b_off, &lbcount, &prev_epos)) {
+		prev_epos.offset = udf_file_entry_alloc_offset(inode);
+		prev_epos.block = iinfo->i_location;
+		prev_epos.bh = NULL;
+	} else {
+		cur_ext_lbcount = prev_ext_lbcount = lbcount;
+	}
+	cur_epos = next_epos = prev_epos;
 
 	/* find the extent which contains the block we are looking for.
 	   alternate between laarr[0] and laarr[1] for locations of the
@@ -626,6 +633,8 @@ static sector_t inode_getblk(struct inode *inode, sector_t block,
 		}
 
 		lbcount += elen;
+		prev_ext_lbcount = cur_ext_lbcount;
+		cur_ext_lbcount += elen;
 
 		prev_epos.block = cur_epos.block;
 		cur_epos.block = next_epos.block;
@@ -649,6 +658,9 @@ static sector_t inode_getblk(struct inode *inode, sector_t block,
 
 		count++;
 	} while (lbcount + elen <= b_off);
+	memcpy(&cache_epos, &prev_epos, sizeof(struct extent_position));
+	if (cache_epos.bh != NULL)
+		get_bh(cache_epos.bh);
 
 	b_off -= lbcount;
 	offset = b_off >> inode->i_sb->s_blocksize_bits;
@@ -669,9 +681,29 @@ static sector_t inode_getblk(struct inode *inode, sector_t block,
 				 ~(inode->i_sb->s_blocksize - 1));
 			udf_write_aext(inode, &cur_epos, &eloc, elen, 1);
 		}
+		/*
+		 * Update extent cache, iterate over laarr[EXTENT_MERGE_SIZE]
+		 * to find the epos corresponding to eloc at laarr[c]
+		 */
+		epos_count = 0;
+		do {
+			etype = udf_next_aext(inode, &cache_epos, &eloc,
+					      &elen, 1);
+			if ((etype == (EXT_RECORDED_ALLOCATED >> 30))
+			    && (laarr[c].extLocation.logicalBlockNum ==
+				eloc.logicalBlockNum)
+			    && (laarr[c].extLocation.partitionReferenceNum ==
+				eloc.partitionReferenceNum)) {
+				udf_update_extent_cache(inode,
+					cur_ext_lbcount, &cache_epos, 1);
+				break;
+			}
+			epos_count++;
+		} while ((etype != -1) && (epos_count < EXTENT_MERGE_SIZE));
 		brelse(prev_epos.bh);
 		brelse(cur_epos.bh);
 		brelse(next_epos.bh);
+		brelse(cache_epos.bh);
 		newblock = udf_get_lb_pblock(inode->i_sb, &eloc, offset);
 		return newblock;
 	}
@@ -699,6 +731,7 @@ static sector_t inode_getblk(struct inode *inode, sector_t block,
 			brelse(prev_epos.bh);
 			brelse(cur_epos.bh);
 			brelse(next_epos.bh);
+			brelse(cache_epos.bh);
 			*err = ret;
 			return 0;
 		}
@@ -716,6 +749,8 @@ static sector_t inode_getblk(struct inode *inode, sector_t block,
 				inode->i_sb->s_blocksize;
 			memset(&laarr[c].extLocation, 0x00,
 				sizeof(struct kernel_lb_addr));
+			if (b_off != 0)
+				cur_ext_lbcount += b_off;
 			count++;
 		}
 		endnum = c + 1;
@@ -744,6 +779,8 @@ static sector_t inode_getblk(struct inode *inode, sector_t block,
 			endnum++;
 		} else
 			lastblock = 1;
+		if (b_off != 0)
+			cur_ext_lbcount += b_off;
 	}
 
 	/* if the current extent is not recorded but allocated, get the
@@ -766,6 +803,7 @@ static sector_t inode_getblk(struct inode *inode, sector_t block,
 			brelse(prev_epos.bh);
 			brelse(cur_epos.bh);
 			brelse(next_epos.bh);
+			brelse(cache_epos.bh);
 			*err = -ENOSPC;
 			return 0;
 		}
@@ -791,16 +829,41 @@ static sector_t inode_getblk(struct inode *inode, sector_t block,
 #endif
 
 	/* merge any continuous blocks in laarr */
+	check_endnum = endnum;
 	udf_merge_extents(inode, laarr, &endnum);
+	if (check_endnum > endnum) {
+		c--;
+		cur_ext_lbcount = prev_ext_lbcount;
+	}
 
 	/* write back the new extents, inserting new extents if the new number
 	 * of extents is greater than the old number, and deleting extents if
 	 * the new number of extents is less than the old number */
 	udf_update_extents(inode, laarr, startnum, endnum, &prev_epos);
 
+	/*
+	 * Update extent cache, iterate over laarr[EXTENT_MERGE_SIZE] to find
+	 * the epos corresponding to eloc at laarr[c]
+	 */
+	epos_count = 0;
+	do {
+		etype = udf_next_aext(inode, &cache_epos, &eloc, &elen, 1);
+		if ((etype == (EXT_RECORDED_ALLOCATED >> 30))
+		    && (laarr[c].extLocation.logicalBlockNum ==
+			eloc.logicalBlockNum)
+		    && (laarr[c].extLocation.partitionReferenceNum ==
+			eloc.partitionReferenceNum)) {
+			udf_update_extent_cache(inode, cur_ext_lbcount,
+						&cache_epos, 1);
+			break;
+		}
+		epos_count++;
+	} while ((etype != -1) && (epos_count < EXTENT_MERGE_SIZE));
+
 	brelse(prev_epos.bh);
 	brelse(cur_epos.bh);
 	brelse(next_epos.bh);
+	brelse(cache_epos.bh);
 
 	newblock = udf_get_pblock(inode->i_sb, newblocknum,
 				iinfo->i_location.partitionReferenceNum, 0);
@@ -1173,6 +1236,7 @@ set_size:
 	} else {
 		if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
 			down_write(&iinfo->i_data_sem);
+			udf_clear_extent_cache(iinfo);
 			memset(iinfo->i_ext.i_data + iinfo->i_lenEAttr + newsize,
 			       0x00, bsize - newsize -
 			       udf_file_entry_alloc_offset(inode));
@@ -1186,6 +1250,7 @@ set_size:
 		if (err)
 			return err;
 		down_write(&iinfo->i_data_sem);
+		udf_clear_extent_cache(iinfo);
 		truncate_setsize(inode, newsize);
 		udf_truncate_extents(inode);
 		up_write(&iinfo->i_data_sem);
@@ -1303,6 +1368,8 @@ static void udf_fill_inode(struct inode *inode, struct buffer_head *bh)
 	iinfo->i_lenAlloc = 0;
 	iinfo->i_next_alloc_block = 0;
 	iinfo->i_next_alloc_goal = 0;
+	memset(&iinfo->cached_extent, 0, sizeof(struct udf_ext_cache));
+	mutex_init(&(iinfo->i_extent_cache_lock));
 	if (fe->descTag.tagIdent == cpu_to_le16(TAG_IDENT_EFE)) {
 		iinfo->i_efe = 1;
 		iinfo->i_use = 0;
@@ -2158,11 +2225,12 @@ int8_t inode_bmap(struct inode *inode, sector_t block,
 	struct udf_inode_info *iinfo;
 
 	iinfo = UDF_I(inode);
-	pos->offset = 0;
-	pos->block = iinfo->i_location;
-	pos->bh = NULL;
+	if (!udf_read_extent_cache(inode, bcount, &lbcount, pos)) {
+		pos->offset = 0;
+		pos->block = iinfo->i_location;
+		pos->bh = NULL;
+	}
 	*elen = 0;
-
 	do {
 		etype = udf_next_aext(inode, pos, eloc, elen, 1);
 		if (etype == -1) {
@@ -2172,7 +2240,8 @@ int8_t inode_bmap(struct inode *inode, sector_t block,
 		}
 		lbcount += *elen;
 	} while (lbcount <= bcount);
-
+	/* update extent cache */
+	udf_update_extent_cache(inode, lbcount - *elen, pos, 1);
 	*offset = (bcount + *elen - lbcount) >> blocksize_bits;
 
 	return etype;
@@ -2202,3 +2271,57 @@ long udf_block_map(struct inode *inode, sector_t block)
 	else
 		return ret;
 }
+int udf_read_extent_cache(struct inode *inode, loff_t bcount,
+			  loff_t *lbcount, struct extent_position *pos)
+{
+	struct udf_inode_info *iinfo = UDF_I(inode);
+	mutex_lock(&iinfo->i_extent_cache_lock);
+	if ((iinfo->cached_extent.lstart <= bcount) &&
+	    (iinfo->cached_extent.valid)) {
+		/* Cache hit */
+		*lbcount = iinfo->cached_extent.lstart;
+		memcpy(pos, &iinfo->cached_extent.epos,
+		       sizeof(struct extent_position));
+		mutex_unlock(&iinfo->i_extent_cache_lock);
+		return 1;
+	}
+	mutex_unlock(&iinfo->i_extent_cache_lock);
+	return 0;
+}
+void udf_update_extent_cache(struct inode *inode, loff_t estart,
+			     struct extent_position *pos, int next_epos)
+{
+	struct udf_inode_info *iinfo = UDF_I(inode);
+	mutex_lock(&iinfo->i_extent_cache_lock);
+	udf_clear_extent_cache(iinfo);
+	if (pos->bh != NULL)
+		/* Increase ref count */
+		get_bh(pos->bh);
+	memcpy(&iinfo->cached_extent.epos, pos,
+	       sizeof(struct extent_position));
+	iinfo->cached_extent.lstart = estart;
+	iinfo->cached_extent.valid = 1;
+	if (next_epos)
+		switch (iinfo->i_alloc_type) {
+		case ICBTAG_FLAG_AD_SHORT:
+			iinfo->cached_extent.epos.offset -=
+			sizeof(struct short_ad);
+			break;
+		case ICBTAG_FLAG_AD_LONG:
+			iinfo->cached_extent.epos.offset -=
+			sizeof(struct long_ad);
+		}
+	mutex_unlock(&iinfo->i_extent_cache_lock);
+}
+
+/* This function should be called after i_data_sem is
+ * held for writing OR i_extent_cache_lock is taken.
+ */
+void udf_clear_extent_cache(struct udf_inode_info *iinfo)
+{
+	if (iinfo->cached_extent.valid) {
+		brelse(iinfo->cached_extent.epos.bh);
+		memset(&iinfo->cached_extent, 0, sizeof(struct udf_ext_cache));
+	}
+}
+
diff --git a/fs/udf/udf_i.h b/fs/udf/udf_i.h
index bb8309d..95e5e17 100644
--- a/fs/udf/udf_i.h
+++ b/fs/udf/udf_i.h
@@ -1,6 +1,20 @@
 #ifndef _UDF_I_H
 #define _UDF_I_H
 
+struct extent_position {
+	struct buffer_head *bh;
+	uint32_t offset;
+	struct kernel_lb_addr block;
+};
+
+struct udf_ext_cache {
+	/* Extent position */
+	struct extent_position epos;
+	/* Start logical offset in bytes */
+	loff_t lstart;
+	bool valid;
+};
+
 /*
  * The i_data_sem and i_mutex serve for protection of allocation information
  * of a regular files and symlinks. This includes all extents belonging to
@@ -35,6 +49,9 @@ struct udf_inode_info {
 		__u8		*i_data;
 	} i_ext;
 	struct rw_semaphore	i_data_sem;
+	struct udf_ext_cache cached_extent;
+	/* Mutex for protecting extent cache */
+	struct mutex i_extent_cache_lock;
 	struct inode vfs_inode;
 };
 
diff --git a/fs/udf/udfdecl.h b/fs/udf/udfdecl.h
index de038da..db4a22e 100644
--- a/fs/udf/udfdecl.h
+++ b/fs/udf/udfdecl.h
@@ -113,11 +113,6 @@ struct ustr {
 	uint8_t u_len;
 };
 
-struct extent_position {
-	struct buffer_head *bh;
-	uint32_t offset;
-	struct kernel_lb_addr block;
-};
 
 /* super.c */
 
@@ -164,6 +159,11 @@ extern int8_t udf_next_aext(struct inode *, struct extent_position *,
 			    struct kernel_lb_addr *, uint32_t *, int);
 extern int8_t udf_current_aext(struct inode *, struct extent_position *,
 			       struct kernel_lb_addr *, uint32_t *, int);
+int udf_read_extent_cache(struct inode *inode, loff_t bcount, loff_t *lbcount,
+			  struct extent_position *pos);
+void udf_update_extent_cache(struct inode *inode, loff_t estart,
+			     struct extent_position *pos, int next_epos);
+void udf_clear_extent_cache(struct udf_inode_info *iinfo);
 
 /* misc.c */
 extern struct buffer_head *udf_tgetblk(struct super_block *, int);
-- 
1.7.9.5

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