[PATCH] ceph: fix __dcache_readdir()

[PATCH] ceph: fix __dcache_readdir()

[Yan, Zheng]

If directory is fragmented, readdir() read its dirfrags one by one.
After reading all dirfrags, the corresponding dentries are sorted in
(frag_t, off) order in the dcache. If dentries of a directory are all
cached, __dcache_readdir() can use the cached dentries to satisfy
readdir syscall. But when checking if a given dentry is after the
the position of readdir, __dcache_readdir() compares numerical value
of frag_t directly. This is wrong, it should use ceph_frag_compare().

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
---
 fs/ceph/dir.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
index 3bbd0eb..42edab9 100644
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -100,6 +100,14 @@ static unsigned fpos_off(loff_t p)
 	return p & 0xffffffff;
 }
 
+static int fpos_cmp(loff_t l, loff_t r)
+{
+	int v = ceph_frag_compare(fpos_frag(l), fpos_frag(r));
+	if (v)
+		return v;
+	return fpos_off(l) > fpos_off(r);
+}
+
 /*
  * When possible, we try to satisfy a readdir by peeking at the
  * dcache.  We make this work by carefully ordering dentries on
@@ -156,7 +164,7 @@ more:
 		if (!d_unhashed(dentry) && dentry->d_inode &&
 		    ceph_snap(dentry->d_inode) != CEPH_SNAPDIR &&
 		    ceph_ino(dentry->d_inode) != CEPH_INO_CEPH &&
-		    ctx->pos <= di->offset)
+		    fpos_cmp(ctx->pos, di->offset) <= 0)
 			break;
 		dout(" skipping %p %.*s at %llu (%llu)%s%s\n", dentry,
 		     dentry->d_name.len, dentry->d_name.name, di->offset,
-- 
1.8.5.3

Re: [PATCH] ceph: fix __dcache_readdir()

[Sage Weil]

Reviewed-by: Sage Weil <sage@inktank.com>

On Thu, 13 Feb 2014, Yan, Zheng wrote:

> If directory is fragmented, readdir() read its dirfrags one by one.
> After reading all dirfrags, the corresponding dentries are sorted in
> (frag_t, off) order in the dcache. If dentries of a directory are all
> cached, __dcache_readdir() can use the cached dentries to satisfy
> readdir syscall. But when checking if a given dentry is after the
> the position of readdir, __dcache_readdir() compares numerical value
> of frag_t directly. This is wrong, it should use ceph_frag_compare().
> 
> Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
> ---
>  fs/ceph/dir.c | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
> index 3bbd0eb..42edab9 100644
> --- a/fs/ceph/dir.c
> +++ b/fs/ceph/dir.c
> @@ -100,6 +100,14 @@ static unsigned fpos_off(loff_t p)
>  	return p & 0xffffffff;
>  }
>  
> +static int fpos_cmp(loff_t l, loff_t r)
> +{
> +	int v = ceph_frag_compare(fpos_frag(l), fpos_frag(r));
> +	if (v)
> +		return v;
> +	return fpos_off(l) > fpos_off(r);
> +}
> +
>  /*
>   * When possible, we try to satisfy a readdir by peeking at the
>   * dcache.  We make this work by carefully ordering dentries on
> @@ -156,7 +164,7 @@ more:
>  		if (!d_unhashed(dentry) && dentry->d_inode &&
>  		    ceph_snap(dentry->d_inode) != CEPH_SNAPDIR &&
>  		    ceph_ino(dentry->d_inode) != CEPH_INO_CEPH &&
> -		    ctx->pos <= di->offset)
> +		    fpos_cmp(ctx->pos, di->offset) <= 0)
>  			break;
>  		dout(" skipping %p %.*s at %llu (%llu)%s%s\n", dentry,
>  		     dentry->d_name.len, dentry->d_name.name, di->offset,
> -- 
> 1.8.5.3
> 
>