From: Alex Tomas 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 valid in the inode's block 2) kernel wants to write inode, but buffer in which inode belongs to gets freed by VM 25-akpm/fs/ext3/inode.c | 121 ++++++++++++++++++++++++++++++++++------ 25-akpm/include/linux/ext3_fs.h | 1 2 files changed, 104 insertions(+), 18 deletions(-) diff -puN fs/ext3/inode.c~ext3-elide-inode-block-reading fs/ext3/inode.c --- 25/fs/ext3/inode.c~ext3-elide-inode-block-reading Thu Jul 10 09:48:35 2003 +++ 25-akpm/fs/ext3/inode.c Thu Jul 10 09:55:06 2003 @@ -2337,26 +2337,114 @@ static unsigned long ext3_get_inode_bloc } /* - * ext3_get_inode_loc returns with an extra refcount against the - * inode's underlying buffer_head on success. + * ext3_get_inode_loc returns with an extra refcount against the inode's + * underlying buffer_head on success. If `in_mem' is false then we're purely + * trying to determine the inode's location on-disk and no read need be + * performed. */ - -int ext3_get_inode_loc (struct inode *inode, struct ext3_iloc *iloc) +static int ext3_get_inode_loc(struct inode *inode, + struct ext3_iloc *iloc, int in_mem) { unsigned long block; + struct buffer_head *bh; block = ext3_get_inode_block(inode->i_sb, inode->i_ino, iloc); - if (block) { - struct buffer_head *bh = sb_bread(inode->i_sb, block); - if (bh) { - iloc->bh = bh; - return 0; - } + if (!block) + return -EIO; + + bh = sb_getblk(inode->i_sb, block); + if (!bh) { ext3_error (inode->i_sb, "ext3_get_inode_loc", - "unable to read inode block - " - "inode=%lu, block=%lu", inode->i_ino, block); + "unable to read inode block - " + "inode=%lu, block=%lu", inode->i_ino, block); + return -EIO; + } + if (!buffer_uptodate(bh)) { + lock_buffer(bh); + if (buffer_uptodate(bh)) { + /* someone brought it uptodate while we waited */ + 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; + struct ext3_group_desc *desc; + int inodes_per_buffer; + int inode_offset, i; + int block_group; + int start; + + /* + * If this is the only valid inode in the block we + * need not read the block. + */ + block_group = (inode->i_ino - 1) / + EXT3_INODES_PER_GROUP(inode->i_sb); + 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); + + /* Is the inode bitmap in cache? */ + desc = ext3_get_group_desc(inode->i_sb, + block_group, NULL); + if (!desc) + goto make_io; + + bitmap_bh = sb_getblk(inode->i_sb, + le32_to_cpu(desc->bg_inode_bitmap)); + if (!bitmap_bh) + goto make_io; + + /* + * If the inode bitmap isn't in cache then the + * optimisation may end up performing two reads instead + * of one, so skip it. + */ + if (!buffer_uptodate(bitmap_bh)) { + brelse(bitmap_bh); + goto make_io; + } + 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 other inodes are free, so skip I/O */ + memset(bh->b_data, 0, bh->b_size); + set_buffer_uptodate(bh); + unlock_buffer(bh); + goto has_buffer; + } + } + +make_io: + /* + * There are another valid inodes in the buffer so we must + * read the block from 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); + brelse(bh); + return -EIO; + } } - return -EIO; +has_buffer: + iloc->bh = bh; + return 0; } void ext3_set_inode_flags(struct inode *inode) @@ -2376,7 +2464,6 @@ void ext3_set_inode_flags(struct inode * inode->i_flags |= S_DIRSYNC; } - void ext3_read_inode(struct inode * inode) { struct ext3_iloc iloc; @@ -2389,7 +2476,7 @@ 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 = ext3_raw_inode(&iloc); @@ -2809,7 +2896,7 @@ 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); @@ -2907,7 +2994,7 @@ 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 include/linux/ext3_fs.h~ext3-elide-inode-block-reading include/linux/ext3_fs.h --- 25/include/linux/ext3_fs.h~ext3-elide-inode-block-reading Thu Jul 10 09:48:35 2003 +++ 25-akpm/include/linux/ext3_fs.h Thu Jul 10 09:55:22 2003 @@ -721,7 +721,6 @@ 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 void ext3_read_inode (struct inode *); extern void ext3_write_inode (struct inode *, int); extern int ext3_setattr (struct dentry *, struct iattr *); _