linux-kernel - Re: [f2fs-dev] [PATCH v3] f2fs: don't use GFP

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Date:   Mon, 9 Apr 2018 20:29:34 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH v3] f2fs: don't use GFP_ZERO for page caches

Change log from v2:
 - consider IO error case when dealing with metapage
 - memset by fill_node_footer

Change log from v1:
 - don't memset for recovered page
 
Related to https://lkml.org/lkml/2018/4/8/661

Sometimes, we need to write meta data to new allocated block address,
then we will allocate a zeroed page in inner inode's address space, and
fill partial data in it, and leave other place with zero value which means
some fields are initial status.

There are two inner inodes (meta inode and node inode) setting __GFP_ZERO,
I have just checked them, for both of them, we can avoid using __GFP_ZERO,
and do initialization by ourselves to avoid unneeded/redundant zeroing
from mm.

Cc: <stable@...r.kernel.org>
Signed-off-by: Chao Yu <yuchao0@...wei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
---
 fs/f2fs/checkpoint.c | 4 +++-
 fs/f2fs/inode.c      | 4 ++--
 fs/f2fs/segment.c    | 3 +++
 fs/f2fs/segment.h    | 1 +
 4 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index bf779461df13..2e23b953d304 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -100,8 +100,10 @@ static struct page *__get_meta_page(struct f2fs_sb_info *sbi, pgoff_t index,
 	 * readonly and make sure do not write checkpoint with non-uptodate
 	 * meta page.
 	 */
-	if (unlikely(!PageUptodate(page)))
+	if (unlikely(!PageUptodate(page))) {
+		memset(page_address(page), 0, PAGE_SIZE);
 		f2fs_stop_checkpoint(sbi, false);
+	}
 out:
 	return page;
 }
diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
index 417c9dcd0269..87535bf63421 100644
--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -320,10 +320,10 @@ struct inode *f2fs_iget(struct super_block *sb, unsigned long ino)
 make_now:
 	if (ino == F2FS_NODE_INO(sbi)) {
 		inode->i_mapping->a_ops = &f2fs_node_aops;
-		mapping_set_gfp_mask(inode->i_mapping, GFP_F2FS_ZERO);
+		mapping_set_gfp_mask(inode->i_mapping, GFP_NOFS);
 	} else if (ino == F2FS_META_INO(sbi)) {
 		inode->i_mapping->a_ops = &f2fs_meta_aops;
-		mapping_set_gfp_mask(inode->i_mapping, GFP_F2FS_ZERO);
+		mapping_set_gfp_mask(inode->i_mapping, GFP_NOFS);
 	} else if (S_ISREG(inode->i_mode)) {
 		inode->i_op = &f2fs_file_inode_operations;
 		inode->i_fop = &f2fs_file_operations;
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index a4b8e3e24ccb..1f5db557ab96 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -2021,6 +2021,7 @@ static void write_current_sum_page(struct f2fs_sb_info *sbi,
 	struct f2fs_summary_block *dst;
 
 	dst = (struct f2fs_summary_block *)page_address(page);
+	memset(dst, 0, PAGE_SIZE);
 
 	mutex_lock(&curseg->curseg_mutex);
 
@@ -3117,6 +3118,7 @@ static void write_compacted_summaries(struct f2fs_sb_info *sbi, block_t blkaddr)
 
 	page = grab_meta_page(sbi, blkaddr++);
 	kaddr = (unsigned char *)page_address(page);
+	memset(kaddr, 0, PAGE_SIZE);
 
 	/* Step 1: write nat cache */
 	seg_i = CURSEG_I(sbi, CURSEG_HOT_DATA);
@@ -3141,6 +3143,7 @@ static void write_compacted_summaries(struct f2fs_sb_info *sbi, block_t blkaddr)
 			if (!page) {
 				page = grab_meta_page(sbi, blkaddr++);
 				kaddr = (unsigned char *)page_address(page);
+				memset(kaddr, 0, PAGE_SIZE);
 				written_size = 0;
 			}
 			summary = (struct f2fs_summary *)(kaddr + written_size);
diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
index 3325d0769723..492ad0c86fa9 100644
--- a/fs/f2fs/segment.h
+++ b/fs/f2fs/segment.h
@@ -375,6 +375,7 @@ static inline void seg_info_to_sit_page(struct f2fs_sb_info *sbi,
 	int i;
 
 	raw_sit = (struct f2fs_sit_block *)page_address(page);
+	memset(raw_sit, 0, PAGE_SIZE);
 	for (i = 0; i < end - start; i++) {
 		rs = &raw_sit->entries[i];
 		se = get_seg_entry(sbi, start + i);
-- 
2.15.0.531.g2ccb3012c9-goog