hi!
Andreas Dilger proposed do not read inode's block during inode updating
if we have enough data to fill that block. here is the patch.
ext3_get_inode_loc() read inode's block only if:
1) this inode has no copy in memory
2) inode's block has another valid inode(s)
this optimization allows to avoid needless I/O in two cases:
1) just allocated inode is first in the inode's block
2) kernel wants to write inode, but buffer in which inode
belongs to gets freed by VM
diff -puN fs/ext3/inode.c~ext3-noread-inode fs/ext3/inode.c
--- linux-2.5.73/fs/ext3/inode.c~ext3-noread-inode Thu Jul 10 12:03:52 2003
+++ linux-2.5.73-alexey/fs/ext3/inode.c Thu Jul 10 14:40:51 2003
@@ -2286,7 +2286,7 @@ out_stop:
* inode's underlying buffer_head on success.
*/
-int ext3_get_inode_loc (struct inode *inode, struct ext3_iloc *iloc)
+int ext3_get_inode_loc (struct inode *inode, struct ext3_iloc *iloc, int in_mem)
{
struct buffer_head *bh = 0;
unsigned long block;
@@ -2328,12 +2328,69 @@ int ext3_get_inode_loc (struct inode *in
EXT3_INODE_SIZE(inode->i_sb);
block = le32_to_cpu(gdp[desc].bg_inode_table) +
(offset >> EXT3_BLOCK_SIZE_BITS(inode->i_sb));
- if (!(bh = sb_bread(inode->i_sb, block))) {
+ if (!(bh = sb_getblk(inode->i_sb, block))) {
ext3_error (inode->i_sb, "ext3_get_inode_loc",
"unable to read inode block - "
"inode=%lu, block=%lu", inode->i_ino, block);
goto bad_inode;
}
+ if (!buffer_uptodate(bh)) {
+ lock_buffer(bh);
+ if (buffer_uptodate(bh)) {
+ /* someone has already initialized buffer */
+ unlock_buffer(bh);
+ goto has_buffer;
+ }
+
+ /* we can't skip I/O if inode is on a disk only */
+ if (in_mem) {
+ struct buffer_head *bitmap_bh;
+ int inodes_per_buffer;
+ int inode_offset, i;
+ int start;
+
+ /*
+ * if this inode is only valid in buffer we need not I/O
+ */
+ inodes_per_buffer = bh->b_size /
+ EXT3_INODE_SIZE(inode->i_sb);
+ inode_offset = ((inode->i_ino - 1) %
+ EXT3_INODES_PER_GROUP(inode->i_sb));
+ start = inode_offset & ~(inodes_per_buffer - 1);
+ bitmap_bh = read_inode_bitmap(inode->i_sb, block_group);
+ for (i = start; i < start + inodes_per_buffer; i++) {
+ if (i == inode_offset)
+ continue;
+ if (ext3_test_bit(i, bitmap_bh->b_data))
+ break;
+ }
+ brelse(bitmap_bh);
+ if (i == start + inodes_per_buffer) {
+ /* all inodes (but our) are free. so, we skip I/O */
+ memset(bh->b_data, 0, bh->b_size);
+ set_buffer_uptodate(bh);
+ unlock_buffer(bh);
+ goto has_buffer;
+ }
+ }
+
+ /*
+ * No, there are another valid inodes in the buffer
+ * so, to preserve them we have to read buffer from
+ * the disk
+ */
+ get_bh(bh);
+ bh->b_end_io = end_buffer_io_sync;
+ submit_bh(READ, bh);
+ wait_on_buffer(bh);
+ if (!buffer_uptodate(bh)) {
+ ext3_error (inode->i_sb, "ext3_get_inode_loc",
+ "unable to read inode block - "
+ "inode=%lu, block=%lu", inode->i_ino, block);
+ goto bad_inode;
+ }
+ }
+ has_buffer:
offset &= (EXT3_BLOCK_SIZE(inode->i_sb) - 1);
iloc->bh = bh;
@@ -2376,7 +2433,7 @@ void ext3_read_inode(struct inode * inod
ei->i_acl = EXT3_ACL_NOT_CACHED;
ei->i_default_acl = EXT3_ACL_NOT_CACHED;
#endif
- if (ext3_get_inode_loc(inode, &iloc))
+ if (ext3_get_inode_loc(inode, &iloc, 0))
goto bad_inode;
bh = iloc.bh;
raw_inode = iloc.raw_inode;
@@ -2781,7 +2838,7 @@ ext3_reserve_inode_write(handle_t *handl
{
int err = 0;
if (handle) {
- err = ext3_get_inode_loc(inode, iloc);
+ err = ext3_get_inode_loc(inode, iloc, 1);
if (!err) {
BUFFER_TRACE(iloc->bh, "get_write_access");
err = ext3_journal_get_write_access(handle, iloc->bh);
@@ -2879,7 +2936,7 @@ ext3_pin_inode(handle_t *handle, struct
int err = 0;
if (handle) {
- err = ext3_get_inode_loc(inode, &iloc);
+ err = ext3_get_inode_loc(inode, &iloc, 1);
if (!err) {
BUFFER_TRACE(iloc.bh, "get_write_access");
err = journal_get_write_access(handle, iloc.bh);
diff -puN fs/ext3/ialloc.c~ext3-noread-inode fs/ext3/ialloc.c
--- linux-2.5.73/fs/ext3/ialloc.c~ext3-noread-inode Thu Jul 10 13:05:37 2003
+++ linux-2.5.73-alexey/fs/ext3/ialloc.c Thu Jul 10 13:06:12 2003
@@ -50,7 +50,7 @@
*
* Return buffer_head of bitmap on success or NULL.
*/
-static struct buffer_head *
+struct buffer_head *
read_inode_bitmap(struct super_block * sb, unsigned long block_group)
{
struct ext3_group_desc *desc;
diff -puN include/linux/ext3_fs.h~ext3-noread-inode include/linux/ext3_fs.h
--- linux-2.5.73/include/linux/ext3_fs.h~ext3-noread-inode Thu Jul 10 13:41:59 2003
+++ linux-2.5.73-alexey/include/linux/ext3_fs.h Thu Jul 10 14:40:13 2003
@@ -717,6 +717,8 @@ extern unsigned long ext3_count_free_ino
extern unsigned long ext3_count_dirs (struct super_block *);
extern void ext3_check_inodes_bitmap (struct super_block *);
extern unsigned long ext3_count_free (struct buffer_head *, unsigned);
+extern struct buffer_head * read_inode_bitmap(struct super_block *, unsigned long);
+
/* inode.c */
@@ -724,7 +726,7 @@ extern int ext3_forget(handle_t *, int,
extern struct buffer_head * ext3_getblk (handle_t *, struct inode *, long, int, int *);
extern struct buffer_head * ext3_bread (handle_t *, struct inode *, int, int, int *);
-extern int ext3_get_inode_loc (struct inode *, struct ext3_iloc *);
+extern int ext3_get_inode_loc (struct inode *, struct ext3_iloc *, int);
extern void ext3_read_inode (struct inode *);
extern void ext3_write_inode (struct inode *, int);
extern int ext3_setattr (struct dentry *, struct iattr *);
_
-
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This archive was generated by hypermail 2b29 : Tue Jul 15 2003 - 22:00:34 EST