Messages in this thread Patch in this message | | | Subject | Re: [PATCH] minor optimization for EXT3 | From | Alex Tomas <> | Date | Thu, 10 Jul 2003 20:46:59 +0000 |
| |
>>>>> Andrew Morton (AM) writes:
AM> ext3_read_inode() got reorganised. Your latest patch will not apply to AM> current kernels.
OK. fixed version:
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
diff -puN fs/ext3/inode.c~ext3-noread-inode fs/ext3/inode.c --- linux-2.5.74/fs/ext3/inode.c~ext3-noread-inode Thu Jul 10 20:05:25 2003 +++ linux-2.5.74-alexey/fs/ext3/inode.c Thu Jul 10 20:25:24 2003 @@ -2339,24 +2339,106 @@ 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. + * in_mem arg enables optimization */ -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) { 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 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; + struct ext3_group_desc *desc; + int inodes_per_buffer; + int inode_offset, i; + int block_group; + int start; + + /* + * if this inode is only valid in buffer we need not I/O + */ + 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); + + /* check is inode bitmap is 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 inode bitmap isn't in cache then we may end up by 2 reads + * instead of 1 read before optimizing. 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 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; + } + } + +make_io: + /* + * 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); + brelse(bh); + return -EIO; + } } - return -EIO; +has_buffer: + iloc->bh = bh; + return 0; } void ext3_set_inode_flags(struct inode *inode) @@ -2389,7 +2471,7 @@ 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); @@ -2793,7 +2875,7 @@ 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); @@ -2891,7 +2973,7 @@ 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-noread-inode include/linux/ext3_fs.h --- linux-2.5.74/include/linux/ext3_fs.h~ext3-noread-inode Thu Jul 10 20:24:39 2003 +++ linux-2.5.74-alexey/include/linux/ext3_fs.h Thu Jul 10 20:25:08 2003 @@ -721,7 +721,7 @@ 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 *); _
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |