linux-kernel - [PATCH 1/2] f2fs: fix missing discard candidates in fstrim

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250102101310.580277-1-guochunhai@vivo.com>
Date: Thu,  2 Jan 2025 03:13:08 -0700
From: Chunhai Guo <guochunhai@...o.com>
To: chao@...nel.org,
	jaegeuk@...nel.org
Cc: linux-f2fs-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org,
	Chunhai Guo <guochunhai@...o.com>
Subject: [PATCH 1/2] f2fs: fix missing discard candidates in fstrim

fstrim may miss candidates that need to be discarded in fstrim, as shown in
the examples below.
The root cause is that when cpc->reason is set with CP_DISCARD,
add_discard_addrs() expects that ckpt_valid_map and cur_valid_map have been
synced by seg_info_to_raw_sit() [1] and tries to find the candidates based
on ckpt_valid_map and discard_map. However, seg_info_to_raw_sit() does not
actually run before f2fs_exist_trim_candidates(), which results in failure.

root# cp testfile /f2fs_mountpoint

root# f2fs_io fiemap 0 1 /f2fs_mountpoint/testfile
Fiemap: offset = 0 len = 1
        logical addr.    physical addr.   length           flags
0       0000000000000000 0000000406a00000 000000003d800000 00001000

root# rm /f2fs_mountpoint/testfile

root# fstrim -v -o 0x406a00000 -l 1024M /f2fs_mountpoint -- no candidate is found
/f2fs_mountpoint: 0 B (0 bytes) trimmed

[1] Please refer to commit d7bc2484b8d4 ("f2fs: fix small discards not to
issue redundantly") for the relationship between seg_info_to_raw_sit() and
add_discard_addrs().

Fixes: 25290fa5591d ("f2fs: return fs_trim if there is no candidate")
Signed-off-by: Chunhai Guo <guochunhai@...o.com>
---
 fs/f2fs/segment.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index eade36c5ef13..8fe9f794b581 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -2070,7 +2070,7 @@ static int f2fs_issue_discard(struct f2fs_sb_info *sbi,
 }
 
 static bool add_discard_addrs(struct f2fs_sb_info *sbi, struct cp_control *cpc,
-							bool check_only)
+					bool synced, bool check_only)
 {
 	int entries = SIT_VBLOCK_MAP_SIZE / sizeof(unsigned long);
 	struct seg_entry *se = get_seg_entry(sbi, cpc->trim_start);
@@ -2098,7 +2098,7 @@ static bool add_discard_addrs(struct f2fs_sb_info *sbi, struct cp_control *cpc,
 
 	/* SIT_VBLOCK_MAP_SIZE should be multiple of sizeof(unsigned long) */
 	for (i = 0; i < entries; i++)
-		dmap[i] = force ? ~ckpt_map[i] & ~discard_map[i] :
+		dmap[i] = synced ? ~ckpt_map[i] & ~discard_map[i] :
 				(cur_map[i] ^ ckpt_map[i]) & ckpt_map[i];
 
 	while (force || SM_I(sbi)->dcc_info->nr_discards <=
@@ -3275,7 +3275,7 @@ bool f2fs_exist_trim_candidates(struct f2fs_sb_info *sbi,
 
 	down_write(&SIT_I(sbi)->sentry_lock);
 	for (; cpc->trim_start <= cpc->trim_end; cpc->trim_start++) {
-		if (add_discard_addrs(sbi, cpc, true)) {
+		if (add_discard_addrs(sbi, cpc, false, true)) {
 			has_candidate = true;
 			break;
 		}
@@ -4611,7 +4611,7 @@ void f2fs_flush_sit_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 			/* add discard candidates */
 			if (!(cpc->reason & CP_DISCARD)) {
 				cpc->trim_start = segno;
-				add_discard_addrs(sbi, cpc, false);
+				add_discard_addrs(sbi, cpc, false, false);
 			}
 
 			if (to_journal) {
@@ -4653,7 +4653,7 @@ void f2fs_flush_sit_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 		__u64 trim_start = cpc->trim_start;
 
 		for (; cpc->trim_start <= cpc->trim_end; cpc->trim_start++)
-			add_discard_addrs(sbi, cpc, false);
+			add_discard_addrs(sbi, cpc, true, false);
 
 		cpc->trim_start = trim_start;
 	}
-- 
2.34.1