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Date:   Wed, 2 Mar 2022 13:06:39 +0800
From:   Gao Xiang <hsiangkao@linux.alibaba.com>
To:     Yue Hu <zbestahu@gmail.com>
Cc:     linux-erofs@lists.ozlabs.org, Chao Yu <chao@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, huyue2@coolpad.com,
        zhangwen@coolpad.com
Subject: Re: [PATCH 1/2] erofs: get rid of `struct z_erofs_collector'
Message-ID: <Yh77X5NWnsHiPKIu@B-P7TQMD6M-0146.local>
References: <20220301194951.106227-1-hsiangkao@linux.alibaba.com>
 <20220302122203.000046f5.zbestahu@gmail.com>
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In-Reply-To: <20220302122203.000046f5.zbestahu@gmail.com>
Precedence: bulk

Hi Yue,

On Wed, Mar 02, 2022 at 12:22:03PM +0800, Yue Hu wrote:
> Hi Xiang,
> 
> On Wed,  2 Mar 2022 03:49:50 +0800
> Gao Xiang <hsiangkao@linux.alibaba.com> wrote:
> 
> > Avoid `struct z_erofs_collector' since there is another context
> > structure called "struct z_erofs_decompress_frontend".
> > 
> > No logic changes.
> > 
> > Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
> > ---
> >  fs/erofs/zdata.c | 163 ++++++++++++++++++++++-------------------------
> >  1 file changed, 77 insertions(+), 86 deletions(-)
> > 
> > diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
> > index 423bc1a61da5..2673fc105861 100644
> > --- a/fs/erofs/zdata.c
> > +++ b/fs/erofs/zdata.c
> > @@ -192,7 +192,10 @@ enum z_erofs_collectmode {
> >  	COLLECT_PRIMARY_FOLLOWED,
> >  };
> >  
> > -struct z_erofs_collector {
> > +struct z_erofs_decompress_frontend {
> > +	struct inode *const inode;
> > +	struct erofs_map_blocks map;
> > +
> >  	struct z_erofs_pagevec_ctor vector;
> >  
> >  	struct z_erofs_pcluster *pcl, *tailpcl;
> > @@ -202,13 +205,6 @@ struct z_erofs_collector {
> >  	z_erofs_next_pcluster_t owned_head;
> >  
> >  	enum z_erofs_collectmode mode;
> > -};
> > -
> > -struct z_erofs_decompress_frontend {
> > -	struct inode *const inode;
> > -
> > -	struct z_erofs_collector clt;
> > -	struct erofs_map_blocks map;
> >  
> >  	bool readahead;
> >  	/* used for applying cache strategy on the fly */
> > @@ -216,30 +212,26 @@ struct z_erofs_decompress_frontend {
> >  	erofs_off_t headoffset;
> >  };
> >  
> > -#define COLLECTOR_INIT() { \
> > -	.owned_head = Z_EROFS_PCLUSTER_TAIL, \
> > -	.mode = COLLECT_PRIMARY_FOLLOWED }
> > -
> >  #define DECOMPRESS_FRONTEND_INIT(__i) { \
> > -	.inode = __i, .clt = COLLECTOR_INIT(), \
> > -	.backmost = true, }
> > +	.inode = __i, .owned_head = Z_EROFS_PCLUSTER_TAIL, \
> > +	.mode = COLLECT_PRIMARY_FOLLOWED }
> >  
> >  static struct page *z_pagemap_global[Z_EROFS_VMAP_GLOBAL_PAGES];
> >  static DEFINE_MUTEX(z_pagemap_global_lock);
> >  
> > -static void preload_compressed_pages(struct z_erofs_collector *clt,
> > +static void preload_compressed_pages(struct z_erofs_decompress_frontend *fe,
> >  				     struct address_space *mc,
> >  				     enum z_erofs_cache_alloctype type,
> >  				     struct page **pagepool)
> >  {
> > -	struct z_erofs_pcluster *pcl = clt->pcl;
> > +	struct z_erofs_pcluster *pcl = fe->pcl;
> >  	bool standalone = true;
> >  	gfp_t gfp = (mapping_gfp_mask(mc) & ~__GFP_DIRECT_RECLAIM) |
> >  			__GFP_NOMEMALLOC | __GFP_NORETRY | __GFP_NOWARN;
> >  	struct page **pages;
> >  	pgoff_t index;
> >  
> > -	if (clt->mode < COLLECT_PRIMARY_FOLLOWED)
> > +	if (fe->mode < COLLECT_PRIMARY_FOLLOWED)
> >  		return;
> >  
> >  	pages = pcl->compressed_pages;
> > @@ -288,7 +280,7 @@ static void preload_compressed_pages(struct z_erofs_collector *clt,
> >  	 * managed cache since it can be moved to the bypass queue instead.
> >  	 */
> >  	if (standalone)
> > -		clt->mode = COLLECT_PRIMARY_FOLLOWED_NOINPLACE;
> > +		fe->mode = COLLECT_PRIMARY_FOLLOWED_NOINPLACE;
> >  }
> >  
> >  /* called by erofs_shrinker to get rid of all compressed_pages */
> > @@ -350,47 +342,47 @@ int erofs_try_to_free_cached_page(struct page *page)
> >  }
> >  
> >  /* page_type must be Z_EROFS_PAGE_TYPE_EXCLUSIVE */
> > -static bool z_erofs_try_inplace_io(struct z_erofs_collector *clt,
> > +static bool z_erofs_try_inplace_io(struct z_erofs_decompress_frontend *fe,
> >  				   struct page *page)
> >  {
> > -	struct z_erofs_pcluster *const pcl = clt->pcl;
> > +	struct z_erofs_pcluster *const pcl = fe->pcl;
> >  
> > -	while (clt->icpage_ptr > pcl->compressed_pages)
> > -		if (!cmpxchg(--clt->icpage_ptr, NULL, page))
> > +	while (fe->icpage_ptr > pcl->compressed_pages)
> > +		if (!cmpxchg(--fe->icpage_ptr, NULL, page))
> >  			return true;
> >  	return false;
> >  }
> >  
> >  /* callers must be with collection lock held */
> > -static int z_erofs_attach_page(struct z_erofs_collector *clt,
> > +static int z_erofs_attach_page(struct z_erofs_decompress_frontend *fe,
> >  			       struct page *page, enum z_erofs_page_type type,
> >  			       bool pvec_safereuse)
> >  {
> >  	int ret;
> >  
> >  	/* give priority for inplaceio */
> > -	if (clt->mode >= COLLECT_PRIMARY &&
> > +	if (fe->mode >= COLLECT_PRIMARY &&
> >  	    type == Z_EROFS_PAGE_TYPE_EXCLUSIVE &&
> > -	    z_erofs_try_inplace_io(clt, page))
> > +	    z_erofs_try_inplace_io(fe, page))
> >  		return 0;
> >  
> > -	ret = z_erofs_pagevec_enqueue(&clt->vector, page, type,
> > +	ret = z_erofs_pagevec_enqueue(&fe->vector, page, type,
> >  				      pvec_safereuse);
> > -	clt->cl->vcnt += (unsigned int)ret;
> > +	fe->cl->vcnt += (unsigned int)ret;
> >  	return ret ? 0 : -EAGAIN;
> >  }
> >  
> > -static void z_erofs_try_to_claim_pcluster(struct z_erofs_collector *clt)
> > +static void z_erofs_try_to_claim_pcluster(struct z_erofs_decompress_frontend *f)
> >  {
> > -	struct z_erofs_pcluster *pcl = clt->pcl;
> > -	z_erofs_next_pcluster_t *owned_head = &clt->owned_head;
> > +	struct z_erofs_pcluster *pcl = f->pcl;
> > +	z_erofs_next_pcluster_t *owned_head = &f->owned_head;
> >  
> >  	/* type 1, nil pcluster (this pcluster doesn't belong to any chain.) */
> >  	if (cmpxchg(&pcl->next, Z_EROFS_PCLUSTER_NIL,
> >  		    *owned_head) == Z_EROFS_PCLUSTER_NIL) {
> >  		*owned_head = &pcl->next;
> >  		/* so we can attach this pcluster to our submission chain. */
> > -		clt->mode = COLLECT_PRIMARY_FOLLOWED;
> > +		f->mode = COLLECT_PRIMARY_FOLLOWED;
> >  		return;
> >  	}
> >  
> > @@ -401,24 +393,24 @@ static void z_erofs_try_to_claim_pcluster(struct z_erofs_collector *clt)
> >  	if (cmpxchg(&pcl->next, Z_EROFS_PCLUSTER_TAIL,
> >  		    *owned_head) == Z_EROFS_PCLUSTER_TAIL) {
> >  		*owned_head = Z_EROFS_PCLUSTER_TAIL;
> > -		clt->mode = COLLECT_PRIMARY_HOOKED;
> > -		clt->tailpcl = NULL;
> > +		f->mode = COLLECT_PRIMARY_HOOKED;
> > +		f->tailpcl = NULL;
> >  		return;
> >  	}
> >  	/* type 3, it belongs to a chain, but it isn't the end of the chain */
> > -	clt->mode = COLLECT_PRIMARY;
> > +	f->mode = COLLECT_PRIMARY;
> >  }
> >  
> > -static int z_erofs_lookup_collection(struct z_erofs_collector *clt,
> > +static int z_erofs_lookup_collection(struct z_erofs_decompress_frontend *fe,
> >  				     struct inode *inode,
> >  				     struct erofs_map_blocks *map)
> >  {
> > -	struct z_erofs_pcluster *pcl = clt->pcl;
> > +	struct z_erofs_pcluster *pcl = fe->pcl;
> >  	struct z_erofs_collection *cl;
> >  	unsigned int length;
> >  
> >  	/* to avoid unexpected loop formed by corrupted images */
> > -	if (clt->owned_head == &pcl->next || pcl == clt->tailpcl) {
> > +	if (fe->owned_head == &pcl->next || pcl == fe->tailpcl) {
> >  		DBG_BUGON(1);
> >  		return -EFSCORRUPTED;
> >  	}
> > @@ -449,15 +441,15 @@ static int z_erofs_lookup_collection(struct z_erofs_collector *clt,
> >  	}
> >  	mutex_lock(&cl->lock);
> >  	/* used to check tail merging loop due to corrupted images */
> > -	if (clt->owned_head == Z_EROFS_PCLUSTER_TAIL)
> > -		clt->tailpcl = pcl;
> > +	if (fe->owned_head == Z_EROFS_PCLUSTER_TAIL)
> > +		fe->tailpcl = pcl;
> >  
> > -	z_erofs_try_to_claim_pcluster(clt);
> > -	clt->cl = cl;
> > +	z_erofs_try_to_claim_pcluster(fe);
> > +	fe->cl = cl;
> >  	return 0;
> >  }
> >  
> > -static int z_erofs_register_collection(struct z_erofs_collector *clt,
> > +static int z_erofs_register_collection(struct z_erofs_decompress_frontend *fe,
> >  				       struct inode *inode,
> >  				       struct erofs_map_blocks *map)
> >  {
> > @@ -485,8 +477,8 @@ static int z_erofs_register_collection(struct z_erofs_collector *clt,
> >  			Z_EROFS_PCLUSTER_FULL_LENGTH : 0);
> >  
> >  	/* new pclusters should be claimed as type 1, primary and followed */
> > -	pcl->next = clt->owned_head;
> > -	clt->mode = COLLECT_PRIMARY_FOLLOWED;
> > +	pcl->next = fe->owned_head;
> > +	fe->mode = COLLECT_PRIMARY_FOLLOWED;
> >  
> >  	cl = z_erofs_primarycollection(pcl);
> >  	cl->pageofs = map->m_la & ~PAGE_MASK;
> > @@ -512,18 +504,18 @@ static int z_erofs_register_collection(struct z_erofs_collector *clt,
> >  		}
> >  
> >  		if (grp != &pcl->obj) {
> > -			clt->pcl = container_of(grp,
> > +			fe->pcl = container_of(grp,
> >  					struct z_erofs_pcluster, obj);
> >  			err = -EEXIST;
> >  			goto err_out;
> >  		}
> >  	}
> >  	/* used to check tail merging loop due to corrupted images */
> > -	if (clt->owned_head == Z_EROFS_PCLUSTER_TAIL)
> > -		clt->tailpcl = pcl;
> > -	clt->owned_head = &pcl->next;
> > -	clt->pcl = pcl;
> > -	clt->cl = cl;
> > +	if (fe->owned_head == Z_EROFS_PCLUSTER_TAIL)
> > +		fe->tailpcl = pcl;
> > +	fe->owned_head = &pcl->next;
> > +	fe->pcl = pcl;
> > +	fe->cl = cl;
> >  	return 0;
> >  
> >  err_out:
> > @@ -532,18 +524,18 @@ static int z_erofs_register_collection(struct z_erofs_collector *clt,
> >  	return err;
> >  }
> >  
> > -static int z_erofs_collector_begin(struct z_erofs_collector *clt,
> > +static int z_erofs_collector_begin(struct z_erofs_decompress_frontend *fe,
> >  				   struct inode *inode,
> >  				   struct erofs_map_blocks *map)
> >  {
> >  	struct erofs_workgroup *grp;
> >  	int ret;
> >  
> > -	DBG_BUGON(clt->cl);
> > +	DBG_BUGON(fe->cl);
> >  
> >  	/* must be Z_EROFS_PCLUSTER_TAIL or pointed to previous collection */
> > -	DBG_BUGON(clt->owned_head == Z_EROFS_PCLUSTER_NIL);
> > -	DBG_BUGON(clt->owned_head == Z_EROFS_PCLUSTER_TAIL_CLOSED);
> > +	DBG_BUGON(fe->owned_head == Z_EROFS_PCLUSTER_NIL);
> > +	DBG_BUGON(fe->owned_head == Z_EROFS_PCLUSTER_TAIL_CLOSED);
> >  
> >  	if (map->m_flags & EROFS_MAP_META) {
> >  		if ((map->m_pa & ~PAGE_MASK) + map->m_plen > PAGE_SIZE) {
> > @@ -555,28 +547,28 @@ static int z_erofs_collector_begin(struct z_erofs_collector *clt,
> >  
> >  	grp = erofs_find_workgroup(inode->i_sb, map->m_pa >> PAGE_SHIFT);
> >  	if (grp) {
> > -		clt->pcl = container_of(grp, struct z_erofs_pcluster, obj);
> > +		fe->pcl = container_of(grp, struct z_erofs_pcluster, obj);
> >  	} else {
> >  tailpacking:
> > -		ret = z_erofs_register_collection(clt, inode, map);
> > +		ret = z_erofs_register_collection(fe, inode, map);
> >  		if (!ret)
> >  			goto out;
> >  		if (ret != -EEXIST)
> >  			return ret;
> >  	}
> >  
> > -	ret = z_erofs_lookup_collection(clt, inode, map);
> > +	ret = z_erofs_lookup_collection(fe, inode, map);
> >  	if (ret) {
> > -		erofs_workgroup_put(&clt->pcl->obj);
> > +		erofs_workgroup_put(&fe->pcl->obj);
> >  		return ret;
> >  	}
> >  
> >  out:
> > -	z_erofs_pagevec_ctor_init(&clt->vector, Z_EROFS_NR_INLINE_PAGEVECS,
> > -				  clt->cl->pagevec, clt->cl->vcnt);
> > +	z_erofs_pagevec_ctor_init(&fe->vector, Z_EROFS_NR_INLINE_PAGEVECS,
> > +				  fe->cl->pagevec, fe->cl->vcnt);
> >  	/* since file-backed online pages are traversed in reverse order */
> > -	clt->icpage_ptr = clt->pcl->compressed_pages +
> > -			z_erofs_pclusterpages(clt->pcl);
> > +	fe->icpage_ptr = fe->pcl->compressed_pages +
> > +			z_erofs_pclusterpages(fe->pcl);
> >  	return 0;
> >  }
> >  
> > @@ -610,24 +602,24 @@ static void z_erofs_collection_put(struct z_erofs_collection *cl)
> >  	erofs_workgroup_put(&pcl->obj);
> >  }
> >  
> > -static bool z_erofs_collector_end(struct z_erofs_collector *clt)
> > +static bool z_erofs_collector_end(struct z_erofs_decompress_frontend *fe)
> >  {
> > -	struct z_erofs_collection *cl = clt->cl;
> > +	struct z_erofs_collection *cl = fe->cl;
> >  
> >  	if (!cl)
> >  		return false;
> >  
> > -	z_erofs_pagevec_ctor_exit(&clt->vector, false);
> > +	z_erofs_pagevec_ctor_exit(&fe->vector, false);
> >  	mutex_unlock(&cl->lock);
> >  
> >  	/*
> >  	 * if all pending pages are added, don't hold its reference
> >  	 * any longer if the pcluster isn't hosted by ourselves.
> >  	 */
> > -	if (clt->mode < COLLECT_PRIMARY_FOLLOWED_NOINPLACE)
> > +	if (fe->mode < COLLECT_PRIMARY_FOLLOWED_NOINPLACE)
> >  		z_erofs_collection_put(cl);
> >  
> > -	clt->cl = NULL;
> > +	fe->cl = NULL;
> >  	return true;
> >  }
> >  
> > @@ -651,7 +643,6 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
> >  	struct inode *const inode = fe->inode;
> >  	struct erofs_sb_info *const sbi = EROFS_I_SB(inode);
> >  	struct erofs_map_blocks *const map = &fe->map;
> > -	struct z_erofs_collector *const clt = &fe->clt;
> >  	const loff_t offset = page_offset(page);
> >  	bool tight = true;
> >  
> > @@ -672,7 +663,7 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
> >  	if (offset + cur >= map->m_la &&
> >  	    offset + cur < map->m_la + map->m_llen) {
> >  		/* didn't get a valid collection previously (very rare) */
> > -		if (!clt->cl)
> > +		if (!fe->cl)
> >  			goto restart_now;
> >  		goto hitted;
> >  	}
> > @@ -680,7 +671,7 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
> >  	/* go ahead the next map_blocks */
> >  	erofs_dbg("%s: [out-of-range] pos %llu", __func__, offset + cur);
> >  
> > -	if (z_erofs_collector_end(clt))
> > +	if (z_erofs_collector_end(fe))
> >  		fe->backmost = false;
> >  
> >  	map->m_la = offset + cur;
> > @@ -693,11 +684,11 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
> >  	if (!(map->m_flags & EROFS_MAP_MAPPED))
> >  		goto hitted;
> >  
> > -	err = z_erofs_collector_begin(clt, inode, map);
> > +	err = z_erofs_collector_begin(fe, inode, map);
> 
> now, we can get 'inode' and 'map' from 'fe'. so, it should be z_erofs_collector_begin(fe)?
> if it's, need to change z_erofs_{register | lookup}_collection() correspondingly. 

This is just a trivial cleanup (just merge `collector' into `frontend').

We can update them in the following patches. Also I'd like to rename
`collection' concept as well. However, since I'm not a native English
speaker, I didn't find a more proper name though.

Thanks,
Gao Xiang