This can fix dbenchthreads/aim7 regressions from 39-rc1 kernel, that caused by path_init_rcu/path_init merge. Regards! Alex >-----Original Message----- >From: Tim Chen [mailto:tim.c.chen@xxxxxxxxxxxxxxx] >Sent: Saturday, April 16, 2011 2:39 AM >To: Alexander Viro; Nick Piggin >Cc: Andi Kleen; linux-fsdevel@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Li, Shaohua; Shi, Alex >Subject: [PATCH] vfs: Fix RCU path walk failiures due to uninitialized nameidata seq number for root directory > >During RCU walk in path_lookupat and path_openat, the rcu lookup >frequently failed because when root directory was looked up, seq number >was not properly set in nameidata. We dropped out of RCU walk in >nameidata_drop_rcu due to mismatch in directory entry's seq number. We >reverted to slow path walk that need to take references. > >With the following patch, I saw a 50% increase in an exim mail server >benchmark throughput on a 4-socket Nehalem-EX system. > >Thanks. > >Tim > >Signed-off-by: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx> >diff --git a/fs/namei.c b/fs/namei.c >index 3cb616d..e4b27a6 100644 >--- a/fs/namei.c >+++ b/fs/namei.c >@@ -697,6 +697,7 @@ static __always_inline void set_root_rcu(struct nameidata *nd) > do { > seq = read_seqcount_begin(&fs->seq); > nd->root = fs->root; >+ nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq); > } while (read_seqcount_retry(&fs->seq, seq)); > } > } > -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
