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In-Reply-To: <20220223211305.296816-11-trondmy@kernel.org>
From:   Anna Schumaker <schumaker.anna@gmail.com>
Date:   Thu, 24 Feb 2022 11:55:45 -0500
Message-ID: <CAFX2JfmLvuh2KROa_tP=_RBXbUg68E--JHutgh1xKPV9en5sfg@mail.gmail.com>
Subject: Re: [PATCH v7 10/21] NFS: Reduce use of uncached readdir
To:     trondmy@kernel.org
Cc:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi Trond,

On Wed, Feb 23, 2022 at 8:25 PM <trondmy@kernel.org> wrote:
>
> From: Trond Myklebust <trond.myklebust@hammerspace.com>
>
> When reading a very large directory, we want to try to keep the page
> cache up to date if doing so is inexpensive. With the change to allow
> readdir to continue reading even when the cache is incomplete, we no
> longer need to fall back to uncached readdir in order to scale to large
> directories.
>
> Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

As of this patch, cthon tests are passing again.

Anna


Anna

> ---
>  fs/nfs/dir.c | 23 +++--------------------
>  1 file changed, 3 insertions(+), 20 deletions(-)
>
> diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
> index 9b0f13b52dbf..982b5dbe30d7 100644
> --- a/fs/nfs/dir.c
> +++ b/fs/nfs/dir.c
> @@ -986,28 +986,11 @@ static int find_and_lock_cache_page(struct nfs_readdir_descriptor *desc)
>         return res;
>  }
>
> -static bool nfs_readdir_dont_search_cache(struct nfs_readdir_descriptor *desc)
> -{
> -       struct address_space *mapping = desc->file->f_mapping;
> -       struct inode *dir = file_inode(desc->file);
> -       unsigned int dtsize = NFS_SERVER(dir)->dtsize;
> -       loff_t size = i_size_read(dir);
> -
> -       /*
> -        * Default to uncached readdir if the page cache is empty, and
> -        * we're looking for a non-zero cookie in a large directory.
> -        */
> -       return desc->dir_cookie != 0 && mapping->nrpages == 0 && size > dtsize;
> -}
> -
>  /* Search for desc->dir_cookie from the beginning of the page cache */
>  static int readdir_search_pagecache(struct nfs_readdir_descriptor *desc)
>  {
>         int res;
>
> -       if (nfs_readdir_dont_search_cache(desc))
> -               return -EBADCOOKIE;
> -
>         do {
>                 if (desc->page_index == 0) {
>                         desc->current_index = 0;
> @@ -1262,10 +1245,10 @@ static loff_t nfs_llseek_dir(struct file *filp, loff_t offset, int whence)
>         }
>         if (offset != filp->f_pos) {
>                 filp->f_pos = offset;
> -               if (!nfs_readdir_use_cookie(filp)) {
> +               dir_ctx->page_index = 0;
> +               if (!nfs_readdir_use_cookie(filp))
>                         dir_ctx->dir_cookie = 0;
> -                       dir_ctx->page_index = 0;
> -               } else
> +               else
>                         dir_ctx->dir_cookie = offset;
>                 if (offset == 0)
>                         memset(dir_ctx->verf, 0, sizeof(dir_ctx->verf));
> --
> 2.35.1
>