From cca9f93a52d2ead50b5da59ca83d5f469ee4be5f Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Thu, 27 Jun 2013 16:04:49 +1000 Subject: [PATCH] xfs: don't do IO when creating an new inode When we are allocating a new inode, we read the inode cluster off disk to increment the generation number. We are already using a random generation number for newly allocated inodes, so if we are not using the ikeep mode, we can just generate a new generation number when we initialise the newly allocated inode. This avoids the need for reading the inode buffer during inode creation. This will speed up allocation of inodes in cold, partially allocated clusters as they will no longer need to be read from disk during allocation. It will also reduce the CPU overhead of inode allocation by not having the process the buffer read, even on cache hits. Signed-off-by: Dave Chinner Reviewed-by: Mark Tinguely Signed-off-by: Ben Myers --- fs/xfs/xfs_inode.c | 36 ++++++++++++++++++++++++++++-------- 1 file changed, 28 insertions(+), 8 deletions(-) diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c index 7f7be5f..d1f76da 100644 --- a/fs/xfs/xfs_inode.c +++ b/fs/xfs/xfs_inode.c @@ -1028,6 +1028,11 @@ xfs_dinode_calc_crc( /* * Read the disk inode attributes into the in-core inode structure. + * + * If we are initialising a new inode and we are not utilising the + * XFS_MOUNT_IKEEP inode cluster mode, we can simple build the new inode core + * with a random generation number. If we are keeping inodes around, we need to + * read the inode cluster to get the existing generation number off disk. */ int xfs_iread( @@ -1047,6 +1052,22 @@ xfs_iread( if (error) return error; + /* shortcut IO on inode allocation if possible */ + if ((iget_flags & XFS_IGET_CREATE) && + !(mp->m_flags & XFS_MOUNT_IKEEP)) { + /* initialise the on-disk inode core */ + memset(&ip->i_d, 0, sizeof(ip->i_d)); + ip->i_d.di_magic = XFS_DINODE_MAGIC; + ip->i_d.di_gen = prandom_u32(); + if (xfs_sb_version_hascrc(&mp->m_sb)) { + ip->i_d.di_version = 3; + ip->i_d.di_ino = ip->i_ino; + uuid_copy(&ip->i_d.di_uuid, &mp->m_sb.sb_uuid); + } else + ip->i_d.di_version = 2; + return 0; + } + /* * Get pointers to the on-disk inode and the buffer containing it. */ @@ -1133,17 +1154,16 @@ xfs_iread( xfs_buf_set_ref(bp, XFS_INO_REF); /* - * Use xfs_trans_brelse() to release the buffer containing the - * on-disk inode, because it was acquired with xfs_trans_read_buf() - * in xfs_imap_to_bp() above. If tp is NULL, this is just a normal + * Use xfs_trans_brelse() to release the buffer containing the on-disk + * inode, because it was acquired with xfs_trans_read_buf() in + * xfs_imap_to_bp() above. If tp is NULL, this is just a normal * brelse(). If we're within a transaction, then xfs_trans_brelse() * will only release the buffer if it is not dirty within the * transaction. It will be OK to release the buffer in this case, - * because inodes on disk are never destroyed and we will be - * locking the new in-core inode before putting it in the hash - * table where other processes can find it. Thus we don't have - * to worry about the inode being changed just because we released - * the buffer. + * because inodes on disk are never destroyed and we will be locking the + * new in-core inode before putting it in the cache where other + * processes can find it. Thus we don't have to worry about the inode + * being changed just because we released the buffer. */ out_brelse: xfs_trans_brelse(tp, bp); -- 2.7.4