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SubjectRe: very low performance on SCSI disks if device node is in tmpfs
Andrew Morton <akpm@osdl.org> 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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