udf: add extent cache support in case of file reading

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

[JK: Fix bh refcounting issues, simplify initialization]

Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Ashish Sangwan <a.sangwan@samsung.com>
Signed-off-by: Bonggil Bak <bgbak@samsung.com>
Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 80 insertions, 6 deletions

diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index cbae1ed0b7c1..7a12e48ad819 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -67,6 +67,74 @@ static void udf_update_extents(struct inode *,
                                struct extent_position *);
 static int udf_get_block(struct inode *, sector_t, struct buffer_head *, int);
 
+static void __udf_clear_extent_cache(struct inode *inode)
+{
+        struct udf_inode_info *iinfo = UDF_I(inode);
+
+        if (iinfo->cached_extent.lstart != -1) {
+                brelse(iinfo->cached_extent.epos.bh);
+                iinfo->cached_extent.lstart = -1;
+        }
+}
+
+/* Invalidate extent cache */
+static void udf_clear_extent_cache(struct inode *inode)
+{
+        struct udf_inode_info *iinfo = UDF_I(inode);
+
+        spin_lock(&iinfo->i_extent_cache_lock);
+        __udf_clear_extent_cache(inode);
+        spin_unlock(&iinfo->i_extent_cache_lock);
+}
+
+/* Return contents of extent cache */
+static 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);
+        int ret = 0;
+
+        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));
+                if (pos->bh)
+                        get_bh(pos->bh);
+                ret = 1;
+        }
+        spin_unlock(&iinfo->i_extent_cache_lock);
+        return ret;
+}
+
+/* Add extent to extent cache */
+static 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);
+        /* Invalidate previously cached extent */
+        __udf_clear_extent_cache(inode);
+        if (pos->bh)
+                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);
+}
 
 void udf_evict_inode(struct inode *inode)
 {
@@ -90,6 +158,7 @@ void udf_evict_inode(struct inode *inode)
         }
         kfree(iinfo->i_ext.i_data);
         iinfo->i_ext.i_data = NULL;
+        udf_clear_extent_cache(inode);
         if (want_delete) {
                 udf_free_inode(inode);
         }
@@ -105,6 +174,7 @@ 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(inode);
                         udf_truncate_extents(inode);
                         up_write(&iinfo->i_data_sem);
                 }
@@ -372,7 +442,7 @@ static int udf_get_block(struct inode *inode, sector_t block,
                 iinfo->i_next_alloc_goal++;
         }
 
-
+        udf_clear_extent_cache(inode);
         phys = inode_getblk(inode, block, &err, &new);
         if (!phys)
                 goto abort;
@@ -1171,6 +1241,7 @@ set_size:
         } else {
                 if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
                         down_write(&iinfo->i_data_sem);
+                        udf_clear_extent_cache(inode);
                         memset(iinfo->i_ext.i_data + iinfo->i_lenEAttr + newsize,
                                0x00, bsize - newsize -
                                udf_file_entry_alloc_offset(inode));
@@ -1184,6 +1255,7 @@ set_size:
                 if (err)
                         return err;
                 down_write(&iinfo->i_data_sem);
+                udf_clear_extent_cache(inode);
                 truncate_setsize(inode, newsize);
                 udf_truncate_extents(inode);
                 up_write(&iinfo->i_data_sem);
@@ -2156,11 +2228,12 @@ 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) {
@@ -2170,7 +2243,8 @@ 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;