[PATCH] udf: add extent cache support in case of file reading

From: Namjae Jeon
Date: Fri Jan 18 2013 - 21:17:14 EST

From: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>

This patch implements extent caching in case of file reading.
While reading a file, currently, UDF reads metadata serially
which takes a lot of time depending on the number of extents present
in the file. Caching last accessd extent improves metadata read time.
Instead of reading file metadata from start, now we read from
the cached extent.

This patch considerably improves the time spent by CPU in kernel mode.
For example, while reading a 10.9 GB file using dd:
Time before applying patch:
11677022208 bytes (10.9GB) copied, 1529.748921 seconds, 7.3MB/s
real 25m 29.85s
user 0m 12.41s
sys 15m 34.75s

Time after applying patch:
11677022208 bytes (10.9GB) copied, 1469.338231 seconds, 7.6MB/s
real 24m 29.44s
user 0m 15.73s
sys 3m 27.61s

Signed-off-by: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
Signed-off-by: Ashish Sangwan <a.sangwan@xxxxxxxxxxx>
Signed-off-by: Bonggil Bak <bgbak@xxxxxxxxxxx>
---
fs/udf/ialloc.c | 4 +++
fs/udf/inode.c | 79 +++++++++++++++++++++++++++++++++++++++++++++++++-----
fs/udf/udf_i.h | 16 +++++++++++
fs/udf/udfdecl.h | 10 +++----
4 files changed, 98 insertions(+), 11 deletions(-)

diff --git a/fs/udf/ialloc.c b/fs/udf/ialloc.c
index 7e5aae4..0cb208e 100644
--- a/fs/udf/ialloc.c
+++ b/fs/udf/ialloc.c
@@ -117,6 +117,10 @@ 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));
+ spin_lock_init(&(iinfo->i_extent_cache_lock));
+ /* Mark extent cache as invalid for now */
+ iinfo->cached_extent.lstart = -1;
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 e78ef48..86e0469 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -91,6 +91,7 @@ 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);
}
@@ -106,6 +107,7 @@ 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);
}
@@ -373,7 +375,7 @@ static int udf_get_block(struct inode *inode, sector_t block,
iinfo->i_next_alloc_goal++;
}

-
+ udf_clear_extent_cache(iinfo);
phys = inode_getblk(inode, block, &err, &new);
if (!phys)
goto abort;
@@ -1172,6 +1174,7 @@ 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));
@@ -1185,6 +1188,7 @@ 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);
@@ -1302,6 +1306,9 @@ 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));
+ spin_lock_init(&(iinfo->i_extent_cache_lock));
+ iinfo->cached_extent.lstart = -1;
if (fe->descTag.tagIdent == cpu_to_le16(TAG_IDENT_EFE)) {
iinfo->i_efe = 1;
iinfo->i_use = 0;
@@ -2157,11 +2164,12 @@ 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) {
@@ -2171,7 +2179,8 @@ 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;
@@ -2201,3 +2210,61 @@ 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);
+
+ spin_lock(&iinfo->i_extent_cache_lock);
+ if ((iinfo->cached_extent.lstart <= bcount) &&
+ (iinfo->cached_extent.lstart != -1)) {
+ /* Cache hit */
+ *lbcount = iinfo->cached_extent.lstart;
+ memcpy(pos, &iinfo->cached_extent.epos,
+ sizeof(struct extent_position));
+ spin_unlock(&iinfo->i_extent_cache_lock);
+ return 1;
+ } else
+ udf_clear_extent_cache(iinfo);
+ spin_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);
+
+ spin_lock(&iinfo->i_extent_cache_lock);
+ 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;
+ 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);
+ }
+ spin_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.lstart != -1) {
+ brelse(iinfo->cached_extent.epos.bh);
+ memset(&iinfo->cached_extent, 0, sizeof(struct udf_ext_cache));
+ iinfo->cached_extent.lstart = -1;
+ }
+}
+
diff --git a/fs/udf/udf_i.h b/fs/udf/udf_i.h
index bb8309d..b5cd8ed 100644
--- a/fs/udf/udf_i.h
+++ b/fs/udf/udf_i.h
@@ -1,6 +1,19 @@
#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;
+};
+
/*
* 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 +48,9 @@ struct udf_inode_info {
__u8 *i_data;
} i_ext;
struct rw_semaphore i_data_sem;
+ struct udf_ext_cache cached_extent;
+ /* Spinlock for protecting extent cache */
+ spinlock_t 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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