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From: JeffleXu <jefflexu@linux.alibaba.com>
To: David Howells <dhowells@redhat.com>, linux-cachefs@redhat.com
Cc: Trond Myklebust <trondmy@hammerspace.com>,
	Anna Schumaker <anna.schumaker@netapp.com>,
	Steve French <sfrench@samba.org>,
	Dominique Martinet <asmadeus@codewreck.org>,
	Jeff Layton <jlayton@kernel.org>,
	Matthew Wilcox <willy@infradead.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Omar Sandoval <osandov@osandov.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org,
	linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org,
	v9fs-developer@lists.sourceforge.net,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 24/64] netfs: Pass more information on how to deal with a hole in the cache
Date: Mon, 6 Dec 2021 19:42:18 +0800	[thread overview]
Message-ID: <d4167c15-b3ce-73b2-1d66-97d651723305@linux.alibaba.com> (raw)
In-Reply-To: <163819612321.215744.9738308885948264476.stgit@warthog.procyon.org.uk>



On 11/29/21 10:28 PM, David Howells wrote:
> Pass more information to the cache on how to deal with a hole if it
> encounters one when trying to read from the cache.  Three options are
> provided:
> 
>  (1) NETFS_READ_HOLE_IGNORE.  Read the hole along with the data, assuming
>      it to be a punched-out extent by the backing filesystem.
> 
>  (2) NETFS_READ_HOLE_CLEAR.  If there's a hole, erase the requested region
>      of the cache and clear the read buffer.
> 
>  (3) NETFS_READ_HOLE_FAIL.  Fail the read if a hole is detected.
> 
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: linux-cachefs@redhat.com
> ---
> 
>  fs/netfs/read_helper.c |    8 ++++----
>  include/linux/netfs.h  |   11 ++++++++++-
>  2 files changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c
> index 7dc79fa8a1f3..08df413efdf3 100644
> --- a/fs/netfs/read_helper.c
> +++ b/fs/netfs/read_helper.c
> @@ -170,7 +170,7 @@ static void netfs_cache_read_terminated(void *priv, ssize_t transferred_or_error
>   */
>  static void netfs_read_from_cache(struct netfs_read_request *rreq,
>  				  struct netfs_read_subrequest *subreq,
> -				  bool seek_data)
> +				  enum netfs_read_from_hole read_hole)
>  {
>  	struct netfs_cache_resources *cres = &rreq->cache_resources;
>  	struct iov_iter iter;
> @@ -180,7 +180,7 @@ static void netfs_read_from_cache(struct netfs_read_request *rreq,
>  			subreq->start + subreq->transferred,
>  			subreq->len   - subreq->transferred);
>  
> -	cres->ops->read(cres, subreq->start, &iter, seek_data,
> +	cres->ops->read(cres, subreq->start, &iter, read_hole,
>  			netfs_cache_read_terminated, subreq);
>  }
>  
> @@ -466,7 +466,7 @@ static void netfs_rreq_short_read(struct netfs_read_request *rreq,
>  	netfs_get_read_subrequest(subreq);
>  	atomic_inc(&rreq->nr_rd_ops);
>  	if (subreq->source == NETFS_READ_FROM_CACHE)
> -		netfs_read_from_cache(rreq, subreq, true);
> +		netfs_read_from_cache(rreq, subreq, NETFS_READ_HOLE_CLEAR);

Hi I'm not sure why NETFS_READ_HOLE_CLEAR style should be used in 'short
read' case.

Besides,

```
static void netfs_read_from_cache(struct netfs_read_request *rreq,
				  struct netfs_read_subrequest *subreq,
				  enum netfs_read_from_hole read_hole)
{
	struct netfs_cache_resources *cres = &rreq->cache_resources;
	struct iov_iter iter;

	netfs_stat(&netfs_n_rh_read);
	iov_iter_xarray(&iter, READ, &rreq->mapping->i_pages,
			subreq->start + subreq->transferred,
			subreq->len   - subreq->transferred);

	cres->ops->read(cres, subreq->start, &iter, read_hole,
			netfs_cache_read_terminated, subreq);
}
```

I'm not sure why 'subreq->start' is not incremented with
'subreq->transferred' when calling cres->ops->read() in 'short read' case.


>  	else
>  		netfs_read_from_server(rreq, subreq);
>  }
> @@ -794,7 +794,7 @@ static bool netfs_rreq_submit_slice(struct netfs_read_request *rreq,
>  		netfs_read_from_server(rreq, subreq);
>  		break;
>  	case NETFS_READ_FROM_CACHE:
> -		netfs_read_from_cache(rreq, subreq, false);
> +		netfs_read_from_cache(rreq, subreq, NETFS_READ_HOLE_IGNORE);
>  		break;
>  	default:
>  		BUG();




> diff --git a/include/linux/netfs.h b/include/linux/netfs.h
> index 5a46fde65759..b46c39d98bbd 100644
> --- a/include/linux/netfs.h
> +++ b/include/linux/netfs.h
> @@ -196,6 +196,15 @@ struct netfs_read_request_ops {
>  	void (*cleanup)(struct address_space *mapping, void *netfs_priv);
>  };
>  
> +/*
> + * How to handle reading from a hole.
> + */
> +enum netfs_read_from_hole {
> +	NETFS_READ_HOLE_IGNORE,
> +	NETFS_READ_HOLE_CLEAR,
> +	NETFS_READ_HOLE_FAIL,
> +};
> +
>  /*
>   * Table of operations for access to a cache.  This is obtained by
>   * rreq->ops->begin_cache_operation().
> @@ -208,7 +217,7 @@ struct netfs_cache_ops {
>  	int (*read)(struct netfs_cache_resources *cres,
>  		    loff_t start_pos,
>  		    struct iov_iter *iter,
> -		    bool seek_data,
> +		    enum netfs_read_from_hole read_hole,
>  		    netfs_io_terminated_t term_func,
>  		    void *term_func_priv);
>  
> 

-- 
Thanks,
Jeffle

  reply	other threads:[~2021-12-06 11:42 UTC|newest]

Thread overview: 73+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-29 14:22 [PATCH 00/64] fscache, cachefiles: Rewrite David Howells
2021-11-29 14:22 ` [PATCH 01/64] fscache, cachefiles: Disable configuration David Howells
2021-11-29 14:22 ` [PATCH 02/64] cachefiles: Delete the cachefiles driver pending rewrite David Howells
2021-11-29 14:23 ` [PATCH 03/64] fscache: Remove the contents of the fscache driver, " David Howells
2021-11-29 14:23 ` [PATCH 04/64] netfs: Display the netfs inode number in the netfs_read tracepoint David Howells
2021-11-29 14:23 ` [PATCH 05/64] netfs: Pass a flag to ->prepare_write() to say if there's no alloc'd space David Howells
2021-11-29 14:24 ` [PATCH 06/64] fscache: Introduce new driver David Howells
2021-11-29 14:24 ` [PATCH 07/64] fscache: Implement a hash function David Howells
2021-11-29 14:24 ` [PATCH 08/64] fscache: Implement cache registration David Howells
2021-11-29 14:24 ` [PATCH 09/64] fscache: Implement volume registration David Howells
2021-11-29 14:25 ` [PATCH 10/64] fscache: Implement cookie registration David Howells
2021-11-29 14:25 ` [PATCH 11/64] fscache: Implement cache-level access helpers David Howells
2021-11-29 14:25 ` [PATCH 12/64] fscache: Implement volume-level " David Howells
2021-11-29 14:25 ` [PATCH 13/64] fscache: Implement cookie-level " David Howells
2021-11-29 14:26 ` [PATCH 14/64] fscache: Implement functions add/remove a cache David Howells
2021-11-29 14:26 ` [PATCH 15/64] fscache: Provide and use cache methods to lookup/create/free a volume David Howells
2021-11-29 14:26 ` [PATCH 16/64] fscache: Add a function for a cache backend to note an I/O error David Howells
2021-11-29 14:26 ` [PATCH 17/64] fscache: Implement simple cookie state machine David Howells
2021-11-29 14:26 ` [PATCH 18/64] fscache: Implement cookie user counting and resource pinning David Howells
2021-11-29 14:27 ` [PATCH 19/64] fscache: Implement cookie invalidation David Howells
2021-11-29 14:27 ` [PATCH 20/64] fscache: Provide a means to begin an operation David Howells
2021-11-29 14:28 ` [PATCH 21/64] fscache: Count data storage objects in a cache David Howells
2021-11-29 14:28 ` [PATCH 22/64] fscache: Provide read/write stat counters for the cache David Howells
2021-11-29 14:28 ` [PATCH 23/64] fscache: Provide a function to let the netfs update its coherency data David Howells
2021-11-29 14:28 ` [PATCH 24/64] netfs: Pass more information on how to deal with a hole in the cache David Howells
2021-12-06 11:42   ` JeffleXu [this message]
2021-12-09 16:49   ` David Howells
2021-11-29 14:28 ` [PATCH 25/64] fscache: Implement raw I/O interface David Howells
2021-11-29 14:29 ` [PATCH 26/64] fscache: Implement higher-level write " David Howells
2021-11-29 14:29 ` [PATCH 27/64] vfs, fscache: Implement pinning of cache usage for writeback David Howells
2021-11-29 14:29 ` [PATCH 28/64] fscache: Provide a function to note the release of a page David Howells
2021-11-29 14:30 ` [PATCH 29/64] fscache: Provide a function to resize a cookie David Howells
2021-11-29 14:30 ` [PATCH 30/64] cachefiles: Introduce rewritten driver David Howells
2021-11-29 14:30 ` [PATCH 31/64] cachefiles: Define structs David Howells
2021-11-29 14:30 ` [PATCH 32/64] cachefiles: Add some error injection support David Howells
2021-11-29 14:30 ` [PATCH 33/64] cachefiles: Add a couple of tracepoints for logging errors David Howells
2021-11-29 14:31 ` [PATCH 34/64] cachefiles: Add cache error reporting macro David Howells
2021-11-29 14:31 ` [PATCH 35/64] cachefiles: Add security derivation David Howells
2021-11-29 14:31 ` [PATCH 36/64] cachefiles: Register a miscdev and parse commands over it David Howells
2021-11-29 14:31 ` [PATCH 37/64] cachefiles: Provide a function to check how much space there is David Howells
2021-11-29 14:31 ` [PATCH 38/64] vfs, cachefiles: Mark a backing file in use with an inode flag David Howells
2021-11-29 14:31 ` [PATCH 39/64] cachefiles: Implement a function to get/create a directory in the cache David Howells
2021-11-29 14:32 ` [PATCH 40/64] cachefiles: Implement cache registration and withdrawal David Howells
2021-11-29 14:32 ` [PATCH 41/64] cachefiles: Implement volume support David Howells
2021-11-29 14:33 ` [PATCH 42/64] cachefiles: Add tracepoints for calls to the VFS David Howells
2021-11-29 14:33 ` [PATCH 43/64] cachefiles: Implement object lifecycle funcs David Howells
2021-11-29 14:33 ` [PATCH 44/64] cachefiles: Implement key to filename encoding David Howells
2021-12-01  5:46   ` JeffleXu
2021-12-01  8:29   ` David Howells
2021-11-29 14:33 ` [PATCH 45/64] cachefiles: Implement metadata/coherency data storage in xattrs David Howells
2021-11-29 14:33 ` [PATCH 46/64] cachefiles: Mark a backing file in use with an inode flag David Howells
2021-11-29 14:33 ` [PATCH 47/64] cachefiles: Implement culling daemon commands David Howells
2021-11-29 14:34 ` [PATCH 48/64] cachefiles: Implement backing file wrangling David Howells
2021-11-29 14:34 ` [PATCH 49/64] cachefiles: Implement begin and end I/O operation David Howells
2021-11-29 14:34 ` [PATCH 50/64] cachefiles: Implement cookie resize for truncate David Howells
2021-11-29 14:34 ` [PATCH 51/64] cachefiles: Implement the I/O routines David Howells
2021-11-30 16:15   ` Nathan Chancellor
2021-11-30 21:05   ` David Howells
2021-11-29 14:34 ` [PATCH 52/64] cachefiles: Allow cachefiles to actually function David Howells
2021-11-29 14:35 ` [PATCH 53/64] fscache, cachefiles: Display stats of no-space events David Howells
2021-11-29 14:35 ` [PATCH 54/64] fscache, cachefiles: Display stat of culling events David Howells
2021-11-29 14:36 ` [PATCH 55/64] afs: Handle len being extending over page end in write_begin/write_end David Howells
2021-11-29 14:36 ` [PATCH 56/64] afs: Fix afs_write_end() to handle len > page size David Howells
2021-11-29 14:36 ` [PATCH 57/64] afs: Convert afs to use the new fscache API David Howells
2021-11-29 14:37 ` [PATCH 58/64] afs: Copy local writes to the cache when writing to the server David Howells
2021-11-29 14:37 ` [PATCH 59/64] afs: Skip truncation on the server of data we haven't written yet David Howells
2021-11-29 14:37 ` [PATCH 60/64] 9p: Use fscache indexing rewrite and reenable caching David Howells
2021-11-29 14:37 ` [PATCH 61/64] 9p: Copy local writes to the cache when writing to the server David Howells
2021-11-29 14:38 ` [PATCH 62/64] nfs: Convert to new fscache volume/cookie API David Howells
2021-11-29 14:38 ` [PATCH 63/64] cifs: Support fscache indexing rewrite (untested) David Howells
2021-11-29 14:38 ` [PATCH 64/64] fscache: Rewrite documentation David Howells
2021-11-29 18:12 ` [PATCH 00/64] fscache, cachefiles: Rewrite Linus Torvalds
2021-11-29 21:40 ` [PATCH 35/64] cachefiles: Add security derivation David Howells

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