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Subject: [PATCH 07/11] Remove inode_congested()
From:   NeilBrown <neilb@suse.de>
To:     Andrew Morton <akpm@linux-foundation.org>, Jan Kara <jack@suse.cz>,
        Wu Fengguang <fengguang.wu@intel.com>,
        Jaegeuk Kim <jaegeuk@kernel.org>, Chao Yu <chao@kernel.org>,
        Jeff Layton <jlayton@kernel.org>,
        Ilya Dryomov <idryomov@gmail.com>,
        Miklos Szeredi <miklos@szeredi.hu>,
        Trond Myklebust <trond.myklebust@hammerspace.com>,
        Anna Schumaker <anna.schumaker@netapp.com>,
        Ryusuke Konishi <konishi.ryusuke@gmail.com>,
        "Darrick J. Wong" <djwong@kernel.org>,
        Philipp Reisner <philipp.reisner@linbit.com>,
        Lars Ellenberg <lars.ellenberg@linbit.com>,
        Paolo Valente <paolo.valente@linaro.org>,
        Jens Axboe <axboe@kernel.dk>
Cc:     linux-doc@vger.kernel.org, linux-mm@kvack.org,
        linux-nilfs@vger.kernel.org, linux-nfs@vger.kernel.org,
        linux-fsdevel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net, linux-ext4@vger.kernel.org,
        ceph-devel@vger.kernel.org, drbd-dev@lists.linbit.com,
        linux-kernel@vger.kernel.org, linux-block@vger.kernel.org
Date:   Thu, 10 Feb 2022 16:37:52 +1100
Message-ID: <164447147261.23354.14022902241501698367.stgit@noble.brown>
In-Reply-To: <164447124918.23354.17858831070003318849.stgit@noble.brown>
References: <164447124918.23354.17858831070003318849.stgit@noble.brown>
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Precedence: bulk

inode_congested() reports if the backing-device for the inode is
congested.  No bdi reports congestion any more, so this always
returns 'false'.

So remove inode_congested() and related functions, and remove the call
sites, assuming that inode_congested() always returns 'false'.

Signed-off-by: NeilBrown <neilb@suse.de>
---
 fs/fs-writeback.c           |   37 -------------------------------------
 include/linux/backing-dev.h |   22 ----------------------
 mm/fadvise.c                |    5 ++---
 mm/readahead.c              |    6 ------
 mm/vmscan.c                 |   17 +----------------
 5 files changed, 3 insertions(+), 84 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index f8d7fe6db989..42a3dfad40b8 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -893,43 +893,6 @@ void wbc_account_cgroup_owner(struct writeback_control *wbc, struct page *page,
 }
 EXPORT_SYMBOL_GPL(wbc_account_cgroup_owner);
 
-/**
- * inode_congested - test whether an inode is congested
- * @inode: inode to test for congestion (may be NULL)
- * @cong_bits: mask of WB_[a]sync_congested bits to test
- *
- * Tests whether @inode is congested.  @cong_bits is the mask of congestion
- * bits to test and the return value is the mask of set bits.
- *
- * If cgroup writeback is enabled for @inode, the congestion state is
- * determined by whether the cgwb (cgroup bdi_writeback) for the blkcg
- * associated with @inode is congested; otherwise, the root wb's congestion
- * state is used.
- *
- * @inode is allowed to be NULL as this function is often called on
- * mapping->host which is NULL for the swapper space.
- */
-int inode_congested(struct inode *inode, int cong_bits)
-{
-	/*
-	 * Once set, ->i_wb never becomes NULL while the inode is alive.
-	 * Start transaction iff ->i_wb is visible.
-	 */
-	if (inode && inode_to_wb_is_valid(inode)) {
-		struct bdi_writeback *wb;
-		struct wb_lock_cookie lock_cookie = {};
-		bool congested;
-
-		wb = unlocked_inode_to_wb_begin(inode, &lock_cookie);
-		congested = wb_congested(wb, cong_bits);
-		unlocked_inode_to_wb_end(inode, &lock_cookie);
-		return congested;
-	}
-
-	return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);
-}
-EXPORT_SYMBOL_GPL(inode_congested);
-
 /**
  * wb_split_bdi_pages - split nr_pages to write according to bandwidth
  * @wb: target bdi_writeback to split @nr_pages to
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 483979c1b9f4..860b675c2929 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -162,7 +162,6 @@ struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
 				    gfp_t gfp);
 void wb_memcg_offline(struct mem_cgroup *memcg);
 void wb_blkcg_offline(struct blkcg *blkcg);
-int inode_congested(struct inode *inode, int cong_bits);
 
 /**
  * inode_cgwb_enabled - test whether cgroup writeback is enabled on an inode
@@ -390,29 +389,8 @@ static inline void wb_blkcg_offline(struct blkcg *blkcg)
 {
 }
 
-static inline int inode_congested(struct inode *inode, int cong_bits)
-{
-	return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);
-}
-
 #endif	/* CONFIG_CGROUP_WRITEBACK */
 
-static inline int inode_read_congested(struct inode *inode)
-{
-	return inode_congested(inode, 1 << WB_sync_congested);
-}
-
-static inline int inode_write_congested(struct inode *inode)
-{
-	return inode_congested(inode, 1 << WB_async_congested);
-}
-
-static inline int inode_rw_congested(struct inode *inode)
-{
-	return inode_congested(inode, (1 << WB_sync_congested) |
-				      (1 << WB_async_congested));
-}
-
 static inline int bdi_congested(struct backing_dev_info *bdi, int cong_bits)
 {
 	return wb_congested(&bdi->wb, cong_bits);
diff --git a/mm/fadvise.c b/mm/fadvise.c
index d6baa4f451c5..338f16022012 100644
--- a/mm/fadvise.c
+++ b/mm/fadvise.c
@@ -109,9 +109,8 @@ int generic_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
 	case POSIX_FADV_NOREUSE:
 		break;
 	case POSIX_FADV_DONTNEED:
-		if (!inode_write_congested(mapping->host))
-			__filemap_fdatawrite_range(mapping, offset, endbyte,
-						   WB_SYNC_NONE);
+		__filemap_fdatawrite_range(mapping, offset, endbyte,
+					   WB_SYNC_NONE);
 
 		/*
 		 * First and last FULL page! Partial pages are deliberately
diff --git a/mm/readahead.c b/mm/readahead.c
index 35a7ebfcb504..31127d5f909f 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -709,12 +709,6 @@ void page_cache_async_ra(struct readahead_control *ractl,
 
 	folio_clear_readahead(folio);
 
-	/*
-	 * Defer asynchronous read-ahead on IO congestion.
-	 */
-	if (inode_read_congested(ractl->mapping->host))
-		return;
-
 	if (blk_cgroup_congested())
 		return;
 
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 090bfb605ecf..ce8492939bd3 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -989,17 +989,6 @@ static inline int is_page_cache_freeable(struct page *page)
 	return page_count(page) - page_has_private(page) == 1 + page_cache_pins;
 }
 
-static int may_write_to_inode(struct inode *inode)
-{
-	if (current->flags & PF_SWAPWRITE)
-		return 1;
-	if (!inode_write_congested(inode))
-		return 1;
-	if (inode_to_bdi(inode) == current->backing_dev_info)
-		return 1;
-	return 0;
-}
-
 /*
  * We detected a synchronous write error writing a page out.  Probably
  * -ENOSPC.  We need to propagate that into the address_space for a subsequent
@@ -1199,8 +1188,6 @@ static pageout_t pageout(struct page *page, struct address_space *mapping)
 	}
 	if (mapping->a_ops->writepage == NULL)
 		return PAGE_ACTIVATE;
-	if (!may_write_to_inode(mapping->host))
-		return PAGE_KEEP;
 
 	if (clear_page_dirty_for_io(page)) {
 		int res;
@@ -1576,9 +1563,7 @@ static unsigned int shrink_page_list(struct list_head *page_list,
 		 * end of the LRU a second time.
 		 */
 		mapping = page_mapping(page);
-		if (((dirty || writeback) && mapping &&
-		     inode_write_congested(mapping->host)) ||
-		    (writeback && PageReclaim(page)))
+		if (writeback && PageReclaim(page))
 			stat->nr_congested++;
 
 		/*