Re: very low performance on SCSI disks if device node is in tmpfs

[Andrew Morton]

Andrew Morton <akpm@xxxxxxxx> wrote:
>
> Everything there is consistent with "not doing readahead".
>



We need to set file->f_ra _after_ calling blkdev_open(), when inode->i_mapping
points at the right thing.  And we need to get it from
inode->i_mapping->host->i_mapping too, which represents the underlying device.


--- 25/fs/open.c~blockdev-readahead-fix	Tue May 25 15:38:15 2004
+++ 25-akpm/fs/open.c	Tue May 25 15:38:15 2004
@@ -790,7 +790,6 @@ struct file *dentry_open(struct dentry *
 	}
 
 	f->f_mapping = inode->i_mapping;
-	file_ra_state_init(&f->f_ra, f->f_mapping);
 	f->f_dentry = dentry;
 	f->f_vfsmnt = mnt;
 	f->f_pos = 0;
@@ -804,6 +803,8 @@ struct file *dentry_open(struct dentry *
 	}
 	f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 
+	file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
+
 	/* NB: we're sure to have correct a_ops only after f_op->open */
 	if (f->f_flags & O_DIRECT) {
 		if (!f->f_mapping || !f->f_mapping->a_ops ||
_

-
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