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Date:   Mon, 17 Feb 2020 17:45:44 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     <jaegeuk@...nel.org>
CC:     <linux-f2fs-devel@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>, <chao@...nel.org>,
        Chao Yu <yuchao0@...wei.com>
Subject: [PATCH v2] f2fs: introduce DEFAULT_IO_TIMEOUT

As Geert Uytterhoeven reported:

for parameter HZ/50 in congestion_wait(BLK_RW_ASYNC, HZ/50);

On some platforms, HZ can be less than 50, then unexpected 0 timeout
jiffies will be set in congestion_wait().

This patch introduces a macro DEFAULT_IO_TIMEOUT to wrap a determinate
value with msecs_to_jiffies(20) to instead HZ/50 to avoid such issue.

Quoted from Geert Uytterhoeven:

"A timeout of HZ means 1 second.
HZ/50 means 20 ms, but has the risk of being zero, if HZ < 50.

If you want to use a timeout of 20 ms, you best use msecs_to_jiffies(20),
as that takes care of the special cases, and never returns 0."

Signed-off-by: Chao Yu <yuchao0@...wei.com>
---
v2:
- use msecs_to_jiffies(20) instead.
 fs/f2fs/compress.c |  3 ++-
 fs/f2fs/data.c     |  4 ++--
 fs/f2fs/f2fs.h     |  3 +++
 fs/f2fs/gc.c       |  3 ++-
 fs/f2fs/inode.c    |  2 +-
 fs/f2fs/node.c     |  2 +-
 fs/f2fs/recovery.c |  5 +++--
 fs/f2fs/segment.c  | 10 ++++++----
 fs/f2fs/super.c    |  6 ++++--
 9 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
index 0282149aa4c8..b9ea531ffbb6 100644
--- a/fs/f2fs/compress.c
+++ b/fs/f2fs/compress.c
@@ -985,7 +985,8 @@ static int f2fs_write_raw_pages(struct compress_ctx *cc,
 			} else if (ret == -EAGAIN) {
 				ret = 0;
 				cond_resched();
-				congestion_wait(BLK_RW_ASYNC, HZ/50);
+				congestion_wait(BLK_RW_ASYNC,
+						DEFAULT_IO_TIMEOUT);
 				lock_page(cc->rpages[i]);
 				clear_page_dirty_for_io(cc->rpages[i]);
 				goto retry_write;
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 019c91f7b301..a877cc50a4c3 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2332,7 +2332,7 @@ int f2fs_encrypt_one_page(struct f2fs_io_info *fio)
 		/* flush pending IOs and wait for a while in the ENOMEM case */
 		if (PTR_ERR(fio->encrypted_page) == -ENOMEM) {
 			f2fs_flush_merged_writes(fio->sbi);
-			congestion_wait(BLK_RW_ASYNC, HZ/50);
+			congestion_wait(BLK_RW_ASYNC, DEFAULT_IO_TIMEOUT);
 			gfp_flags |= __GFP_NOFAIL;
 			goto retry_encrypt;
 		}
@@ -2923,7 +2923,7 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
 					if (wbc->sync_mode == WB_SYNC_ALL) {
 						cond_resched();
 						congestion_wait(BLK_RW_ASYNC,
-								HZ/50);
+							DEFAULT_IO_TIMEOUT);
 						goto retry_write;
 					}
 					goto next;
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 816a5adb83a4..72c91a6dd549 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -558,6 +558,9 @@ enum {
 
 #define DEFAULT_RETRY_IO_COUNT	8	/* maximum retry read IO count */
 
+/* congestion wait timeout value, default: 20ms */
+#define	DEFAULT_IO_TIMEOUT	(msecs_to_jiffies(20))
+
 /* maximum retry quota flush count */
 #define DEFAULT_RETRY_QUOTA_FLUSH_COUNT		8
 
diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 897de003e423..3db11d5a50d5 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -974,7 +974,8 @@ static int move_data_page(struct inode *inode, block_t bidx, int gc_type,
 		if (err) {
 			clear_cold_data(page);
 			if (err == -ENOMEM) {
-				congestion_wait(BLK_RW_ASYNC, HZ/50);
+				congestion_wait(BLK_RW_ASYNC,
+						DEFAULT_IO_TIMEOUT);
 				goto retry;
 			}
 			if (is_dirty)
diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
index 78c3f1d70f1d..156cc5ef3044 100644
--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -518,7 +518,7 @@ struct inode *f2fs_iget_retry(struct super_block *sb, unsigned long ino)
 	inode = f2fs_iget(sb, ino);
 	if (IS_ERR(inode)) {
 		if (PTR_ERR(inode) == -ENOMEM) {
-			congestion_wait(BLK_RW_ASYNC, HZ/50);
+			congestion_wait(BLK_RW_ASYNC, DEFAULT_IO_TIMEOUT);
 			goto retry;
 		}
 	}
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 9824f055a5bc..d5edbe2ce4a1 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -2602,7 +2602,7 @@ int f2fs_recover_inode_page(struct f2fs_sb_info *sbi, struct page *page)
 retry:
 	ipage = f2fs_grab_cache_page(NODE_MAPPING(sbi), ino, false);
 	if (!ipage) {
-		congestion_wait(BLK_RW_ASYNC, HZ/50);
+		congestion_wait(BLK_RW_ASYNC, DEFAULT_IO_TIMEOUT);
 		goto retry;
 	}
 
diff --git a/fs/f2fs/recovery.c b/fs/f2fs/recovery.c
index 348e8d463b3e..dd804c07eeb0 100644
--- a/fs/f2fs/recovery.c
+++ b/fs/f2fs/recovery.c
@@ -534,7 +534,7 @@ static int do_recover_data(struct f2fs_sb_info *sbi, struct inode *inode,
 	err = f2fs_get_dnode_of_data(&dn, start, ALLOC_NODE);
 	if (err) {
 		if (err == -ENOMEM) {
-			congestion_wait(BLK_RW_ASYNC, HZ/50);
+			congestion_wait(BLK_RW_ASYNC, DEFAULT_IO_TIMEOUT);
 			goto retry_dn;
 		}
 		goto out;
@@ -617,7 +617,8 @@ static int do_recover_data(struct f2fs_sb_info *sbi, struct inode *inode,
 			err = check_index_in_prev_nodes(sbi, dest, &dn);
 			if (err) {
 				if (err == -ENOMEM) {
-					congestion_wait(BLK_RW_ASYNC, HZ/50);
+					congestion_wait(BLK_RW_ASYNC,
+							DEFAULT_IO_TIMEOUT);
 					goto retry_prev;
 				}
 				goto err;
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index c3252603ff79..1628bc8327f1 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -245,7 +245,8 @@ static int __revoke_inmem_pages(struct inode *inode,
 								LOOKUP_NODE);
 			if (err) {
 				if (err == -ENOMEM) {
-					congestion_wait(BLK_RW_ASYNC, HZ/50);
+					congestion_wait(BLK_RW_ASYNC,
+							DEFAULT_IO_TIMEOUT);
 					cond_resched();
 					goto retry;
 				}
@@ -312,7 +313,7 @@ void f2fs_drop_inmem_pages_all(struct f2fs_sb_info *sbi, bool gc_failure)
 skip:
 		iput(inode);
 	}
-	congestion_wait(BLK_RW_ASYNC, HZ/50);
+	congestion_wait(BLK_RW_ASYNC, DEFAULT_IO_TIMEOUT);
 	cond_resched();
 	if (gc_failure) {
 		if (++looped >= count)
@@ -415,7 +416,8 @@ static int __f2fs_commit_inmem_pages(struct inode *inode)
 			err = f2fs_do_write_data_page(&fio);
 			if (err) {
 				if (err == -ENOMEM) {
-					congestion_wait(BLK_RW_ASYNC, HZ/50);
+					congestion_wait(BLK_RW_ASYNC,
+							DEFAULT_IO_TIMEOUT);
 					cond_resched();
 					goto retry;
 				}
@@ -2801,7 +2803,7 @@ static unsigned int __issue_discard_cmd_range(struct f2fs_sb_info *sbi,
 			blk_finish_plug(&plug);
 			mutex_unlock(&dcc->cmd_lock);
 			trimmed += __wait_all_discard_cmd(sbi, NULL);
-			congestion_wait(BLK_RW_ASYNC, HZ/50);
+			congestion_wait(BLK_RW_ASYNC, DEFAULT_IO_TIMEOUT);
 			goto next;
 		}
 skip:
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 1456979222cf..dcfa5836767c 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1884,7 +1884,8 @@ static ssize_t f2fs_quota_read(struct super_block *sb, int type, char *data,
 		page = read_cache_page_gfp(mapping, blkidx, GFP_NOFS);
 		if (IS_ERR(page)) {
 			if (PTR_ERR(page) == -ENOMEM) {
-				congestion_wait(BLK_RW_ASYNC, HZ/50);
+				congestion_wait(BLK_RW_ASYNC,
+						DEFAULT_IO_TIMEOUT);
 				goto repeat;
 			}
 			set_sbi_flag(F2FS_SB(sb), SBI_QUOTA_NEED_REPAIR);
@@ -1938,7 +1939,8 @@ static ssize_t f2fs_quota_write(struct super_block *sb, int type,
 							&page, NULL);
 		if (unlikely(err)) {
 			if (err == -ENOMEM) {
-				congestion_wait(BLK_RW_ASYNC, HZ/50);
+				congestion_wait(BLK_RW_ASYNC,
+						DEFAULT_IO_TIMEOUT);
 				goto retry;
 			}
 			set_sbi_flag(F2FS_SB(sb), SBI_QUOTA_NEED_REPAIR);
-- 
2.18.0.rc1

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