linux-kernel - Re: [PATCH v4 46/68] cachefiles: Mark a backing file in use with an inode flag

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Date:   Thu, 06 Jan 2022 13:04:25 -0500
From:   Jeff Layton <jlayton@...nel.org>
To:     David Howells <dhowells@...hat.com>, linux-cachefs@...hat.com
Cc:     Trond Myklebust <trondmy@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        Steve French <sfrench@...ba.org>,
        Dominique Martinet <asmadeus@...ewreck.org>,
        Matthew Wilcox <willy@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Omar Sandoval <osandov@...ndov.com>,
        JeffleXu <jefflexu@...ux.alibaba.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-afs@...ts.infradead.org, linux-nfs@...r.kernel.org,
        linux-cifs@...r.kernel.org, ceph-devel@...r.kernel.org,
        v9fs-developer@...ts.sourceforge.net,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 46/68] cachefiles: Mark a backing file in use with an
 inode flag

On Wed, 2021-12-22 at 23:25 +0000, David Howells wrote:
> Use an inode flag, S_KERNEL_FILE, to mark that a backing file is in use by
> the kernel to prevent cachefiles or other kernel services from interfering
> with that file.
> 
> Using S_SWAPFILE instead isn't really viable as that has other effects in
> the I/O paths.
> 
> Signed-off-by: David Howells <dhowells@...hat.com>
> cc: linux-cachefs@...hat.com
> Link: https://lore.kernel.org/r/163819642273.215744.6414248677118690672.stgit@warthog.procyon.org.uk/ # v1
> Link: https://lore.kernel.org/r/163906943215.143852.16972351425323967014.stgit@warthog.procyon.org.uk/ # v2
> Link: https://lore.kernel.org/r/163967154118.1823006.13227551961786743991.stgit@warthog.procyon.org.uk/ # v3
> ---
> 
>  fs/cachefiles/internal.h |    2 ++
>  fs/cachefiles/namei.c    |   35 +++++++++++++++++++++++++++++++++++
>  2 files changed, 37 insertions(+)
> 
> diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
> index 01071e7a7c02..7c67a70a3dff 100644
> --- a/fs/cachefiles/internal.h
> +++ b/fs/cachefiles/internal.h
> @@ -187,6 +187,8 @@ extern struct kmem_cache *cachefiles_object_jar;
>  /*
>   * namei.c
>   */
> +extern void cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
> +					   struct file *file);
>  extern struct dentry *cachefiles_get_directory(struct cachefiles_cache *cache,
>  					       struct dentry *dir,
>  					       const char *name,
> diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
> index 11a33209ab5f..db60a671c3fc 100644
> --- a/fs/cachefiles/namei.c
> +++ b/fs/cachefiles/namei.c
> @@ -31,6 +31,18 @@ static bool __cachefiles_mark_inode_in_use(struct cachefiles_object *object,
>  	return can_use;
>  }
>  
> +static bool cachefiles_mark_inode_in_use(struct cachefiles_object *object,
> +					 struct dentry *dentry)
> +{
> +	struct inode *inode = d_backing_inode(dentry);
> +	bool can_use;
> +
> +	inode_lock(inode);
> +	can_use = __cachefiles_mark_inode_in_use(object, dentry);
> +	inode_unlock(inode);
> +	return can_use;
> +}
> +
>  /*
>   * Unmark a backing inode.  The caller must hold the inode lock.
>   */
> @@ -43,6 +55,29 @@ static void __cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
>  	trace_cachefiles_mark_inactive(object, inode);
>  }
>  
> +/*
> + * Unmark a backing inode and tell cachefilesd that there's something that can
> + * be culled.
> + */
> +void cachefiles_unmark_inode_in_use(struct cachefiles_object *object,
> +				    struct file *file)
> +{
> +	struct cachefiles_cache *cache = object->volume->cache;
> +	struct inode *inode = file_inode(file);
> +
> +	if (inode) {
> +		inode_lock(inode);
> +		__cachefiles_unmark_inode_in_use(object, file->f_path.dentry);
> +		inode_unlock(inode);
> +
> +		if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
> +			atomic_long_add(inode->i_blocks, &cache->b_released);
> +			if (atomic_inc_return(&cache->f_released))
> +				cachefiles_state_changed(cache);
> +		}
> +	}
> +}
> +
>  /*
>   * get a subdirectory
>   */
> 
> 

Probably, this patch should be merged with #38. The commit logs are the
same, and they are at least somewhat related.

-- 
Jeff Layton <jlayton@...nel.org>