Re: [PATCH v2] Fix i_mutex handling in nfsd readdir

From: hooanon05
Date: Wed Apr 22 2009 - 00:42:22 EST



David Woodhouse:
> This patch fixes it by locking the directory's i_mutex again before
> calling the filldir functions. The original deadlocks which commit
:::

An entry may be removed between the first mutex_unlock and the second
mutex_lock. In this case, lookup_one_len() in compose_entry_fh() will
return a negative dentry.
Currently the inode test (positive/negative) is done AFTER fh_compose().
Isn't it better to test it BEFORE fh_compose()?

compose_entry_fh()
{
:::
dchild = lookup_one_len(name, dparent, namlen);
if (IS_ERR(dchild))
return 1;
if (d_mountpoint(dchild) ||
fh_compose(fhp, exp, dchild, &cd->fh) != 0 ||
!dchild->d_inode)
rv = 1;
:::
}


J. R. Okajima
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