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([2405:201:682f:3094:a860:817b:dcc:3e4a]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-26980368fe3sm169878605ad.151.2025.09.23.18.16.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Sep 2025 18:16:06 -0700 (PDT) From: Deepanshu Kartikey To: tytso@mit.edu Cc: adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, Deepanshu Kartikey , syzbot+fd3f70a4509fca8c265d@syzkaller.appspotmail.com Subject: [PATCH] ext4: fix allocation failure in ext4_mb_load_buddy_gfp Date: Wed, 24 Sep 2025 06:46:00 +0530 Message-ID: <20250924011600.1095949-1-kartikey406@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Fix WARNING in __alloc_pages_slowpath() when ext4_discard_preallocations() is called during memory pressure. The issue occurs when __GFP_NOFAIL is used during memory reclaim context, which can lead to allocation warnings. Avoid using __GFP_NOFAIL when the current process is already in memory allocation context to prevent potential deadlocks and warnings. Reported-by: syzbot+fd3f70a4509fca8c265d@syzkaller.appspotmail.com Signed-off-by: Deepanshu Kartikey Tested-by: syzbot+fd3f70a4509fca8c265d@syzkaller.appspotmail.com --- fs/ext4/mballoc.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 5898d92ba19f..61ee009717f1 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -5656,9 +5656,11 @@ void ext4_discard_preallocations(struct inode *inode) list_for_each_entry_safe(pa, tmp, &list, u.pa_tmp_list) { BUG_ON(pa->pa_type !=3D MB_INODE_PA); group =3D ext4_get_group_number(sb, pa->pa_pstart); + gfp_t flags =3D GFP_NOFS; + if (!(current->flags & PF_MEMALLOC)) + flags |=3D __GFP_NOFAIL; =20 - err =3D ext4_mb_load_buddy_gfp(sb, group, &e4b, - GFP_NOFS|__GFP_NOFAIL); + err =3D ext4_mb_load_buddy_gfp(sb, group, &e4b, flags); if (err) { ext4_error_err(sb, -err, "Error %d loading buddy information for %u", err, group); --=20 2.43.0