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From: Miklos Szeredi <miklos@szeredi.hu>
To: Amir Goldstein <amir73il@gmail.com>
Cc: Jeff Layton <jlayton@poochiereds.net>,
	"J . Bruce Fields" <bfields@fieldses.org>,
	overlayfs <linux-unionfs@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH v2 10/17] ovl: decode lower file handles of unlinked but open files
Date: Tue, 16 Jan 2018 11:10:38 +0100	[thread overview]
Message-ID: <CAJfpegskFBrjED6JmBZbpJ1eLFufmWKbiNV=gDnzCfdj=qaJAw@mail.gmail.com> (raw)
In-Reply-To: <CAOQ4uxjDvxe-h9Ojy44HunqxniOPQBtFO5xoY9NrR3ypOJ5x+Q@mail.gmail.com>

On Tue, Jan 16, 2018 at 10:37 AM, Amir Goldstein <amir73il@gmail.com> wrote:
> On Tue, Jan 16, 2018 at 11:16 AM, Miklos Szeredi <miklos@szeredi.hu> wrote:
>> On Thu, Jan 4, 2018 at 6:20 PM, Amir Goldstein <amir73il@gmail.com> wrote:
>>> Lookup overlay inode in cache by origin inode, so we can decode a file
>>> handle of an open file even if the index has a whiteout index entry to
>>> mark this overlay inode was unlinked.
>>>
>>> Signed-off-by: Amir Goldstein <amir73il@gmail.com>
>>> ---
>>>  fs/overlayfs/export.c    | 22 ++++++++++++++++++++--
>>>  fs/overlayfs/inode.c     | 16 ++++++++++++++++
>>>  fs/overlayfs/overlayfs.h |  1 +
>>>  3 files changed, 37 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
>>> index 602bada474ba..6ecb54d4b52c 100644
>>> --- a/fs/overlayfs/export.c
>>> +++ b/fs/overlayfs/export.c
>>> @@ -385,13 +385,21 @@ static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
>>>         struct ovl_path *stack = &origin;
>>>         struct dentry *dentry = NULL;
>>>         struct dentry *index = NULL;
>>> +       struct inode *inode = NULL;
>>> +       bool is_deleted = false;
>>>         int err;
>>>
>>>         /* First lookup indexed upper by fh */
>>
>> Why not first look up origin, then look up ovl inode by origin?  It
>> seems a faster path than going through the index first.  Obviously if
>> icache lookup fails then we need to look up index, but the common case
>> will the cached one, so that should be the fast one, no?
>>
>
> Not really, because we do not know if the file handle is dir or non-dir.
> If file handle is dir than decode of file handle is expensive and can
> reduce worst case from two file handle decodes to just one:
>
> For lower dir:
> - one index lookup fails
> - one lower dir decode
> - one icache lookup
> - maybe one ovl_lookup_real(is_upper=false)
>
> For copied up indexed dir:
> - one index lookup success
> - one upper dir decode
> - one ovl_lookup_real(is_upper=true)
>
> That method avoids the origin dir decode for upper indexed
> dir at the cost of not looking for the decoded dir in icache.
>
> How about this as in idea: hash overlay inodes for NFS export
> by origin fh instead of by origin inode pointer.

Good idea.  That way we can leave out the middleman (underlying fh
decode) in the cached case.

> We can also avoid the "lookup index first" for non-dir
> if we set a flag OVL_FH_FLAG_CONNECTABLE on exported
> dir file handle, but my thinking was trying to keep the first version
> simple with as fewer special cases as possible.

Not sure I understand.  If cached lookup fails, then we do always need
to try and lookup index first before falling back to decoding origin,
right?

Thanks,
Miklos




>
> Thanks,
> Amir.

  reply	other threads:[~2018-01-16 10:10 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-04 17:20 [PATCH v2 00/17] Overlayfs NFS export support Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 01/17] ovl: document NFS export Amir Goldstein
2018-01-11 16:06   ` Miklos Szeredi
2018-01-11 16:26     ` Amir Goldstein
2018-01-12 15:43       ` Miklos Szeredi
2018-01-12 15:49         ` Miklos Szeredi
2018-01-12 18:50           ` Amir Goldstein
2018-01-13  8:54           ` Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 02/17] ovl: encode pure upper file handles Amir Goldstein
2018-01-18 10:31   ` Miklos Szeredi
2018-01-04 17:20 ` [PATCH v2 03/17] ovl: decode " Amir Goldstein
2018-01-18 14:09   ` Miklos Szeredi
2018-01-18 14:34     ` Amir Goldstein
2018-01-18 14:39       ` Miklos Szeredi
2018-01-18 19:49         ` Amir Goldstein
2018-01-18 20:10           ` Miklos Szeredi
2018-01-18 20:35             ` Amir Goldstein
2018-01-18 22:57               ` Amir Goldstein
2018-01-19  0:23                 ` Amir Goldstein
2018-01-19 10:39                   ` Miklos Szeredi
2018-01-19 11:07                     ` Amir Goldstein
2018-01-19 20:10                       ` Amir Goldstein
2018-01-24 10:34                         ` Miklos Szeredi
2018-01-24 11:04                           ` Amir Goldstein
2018-01-24 11:18                             ` Amir Goldstein
2018-01-24 11:55                               ` Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 04/17] ovl: decode connected upper dir " Amir Goldstein
2018-01-05 12:33   ` Amir Goldstein
2018-01-05 15:18     ` J . Bruce Fields
2018-01-05 15:34       ` Amir Goldstein
2018-01-15 11:41     ` Miklos Szeredi
2018-01-15 11:33   ` Miklos Szeredi
2018-01-15 12:20     ` Amir Goldstein
2018-01-15 14:56       ` Miklos Szeredi
2018-01-17 11:18         ` Amir Goldstein
2018-01-17 12:20           ` Amir Goldstein
2018-01-17 13:29             ` Amir Goldstein
2018-01-17 15:42           ` Miklos Szeredi
2018-01-17 16:34             ` Amir Goldstein
2018-01-17 21:36               ` Amir Goldstein
2018-01-18  8:22               ` Miklos Szeredi
2018-01-18  8:47                 ` Amir Goldstein
2018-01-18  9:12                   ` Miklos Szeredi
2018-01-18 10:28                     ` Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 05/17] ovl: encode non-indexed upper " Amir Goldstein
2018-01-15 11:58   ` Miklos Szeredi
2018-01-15 12:07     ` Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 06/17] ovl: copy up before encoding dir file handle when ofs->numlower > 1 Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 07/17] ovl: encode lower file handles Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 08/17] ovl: decode lower non-dir " Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 09/17] ovl: decode indexed " Amir Goldstein
2018-01-18 13:11   ` Miklos Szeredi
2018-01-04 17:20 ` [PATCH v2 10/17] ovl: decode lower file handles of unlinked but open files Amir Goldstein
2018-01-16  9:16   ` Miklos Szeredi
2018-01-16  9:37     ` Amir Goldstein
2018-01-16 10:10       ` Miklos Szeredi [this message]
2018-01-16 10:40         ` Amir Goldstein
2018-01-16 11:07           ` Miklos Szeredi
2018-01-17 21:05         ` Amir Goldstein
2018-01-18 14:18   ` Amir Goldstein
2018-02-27 11:35     ` Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 11/17] ovl: decode indexed dir file handles Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 12/17] ovl: decode pure lower " Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 13/17] ovl: hash directory inodes for NFS export Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 14/17] ovl: lookup connected ancestor of dir in inode cache Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 15/17] ovl: lookup indexed ancestor of lower dir Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 16/17] ovl: wire up NFS export support Amir Goldstein
2018-01-04 17:20 ` [PATCH v2 17/17] nfsd: encode stat->mtime for getattr instead of inode->i_mtime Amir Goldstein

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