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[2403:580d:fda1::299]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3540f17955asm9038511a91.0.2026.01.30.18.15.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 30 Jan 2026 18:15:10 -0800 (PST) Message-ID: <9e1bf022-730d-4b93-872a-259490eb4946@suse.com> Date: Sat, 31 Jan 2026 12:45:05 +1030 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] btrfs: guard against missing private state in lock_delalloc_folios() To: JP Kobryn , boris@bur.io, clm@fb.com, dsterba@suse.com Cc: linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com References: <20260131013438.286422-1-inwardvessel@gmail.com> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=wqu@suse.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNGFF1IFdlbnJ1byA8d3F1QHN1c2UuY29tPsLAlAQTAQgAPgIbAwULCQgHAgYVCAkKCwIE FgIDAQIeAQIXgBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXVgBQkQ/lqxAAoJEMI9kfOh Jf6o+jIH/2KhFmyOw4XWAYbnnijuYqb/obGae8HhcJO2KIGcxbsinK+KQFTSZnkFxnbsQ+VY fvtWBHGt8WfHcNmfjdejmy9si2jyy8smQV2jiB60a8iqQXGmsrkuR+AM2V360oEbMF3gVvim 2VSX2IiW9KERuhifjseNV1HLk0SHw5NnXiWh1THTqtvFFY+CwnLN2GqiMaSLF6gATW05/sEd V17MdI1z4+WSk7D57FlLjp50F3ow2WJtXwG8yG8d6S40dytZpH9iFuk12Sbg7lrtQxPPOIEU rpmZLfCNJJoZj603613w/M8EiZw6MohzikTWcFc55RLYJPBWQ+9puZtx1DopW2jOwE0EWdWB rwEIAKpT62HgSzL9zwGe+WIUCMB+nOEjXAfvoUPUwk+YCEDcOdfkkM5FyBoJs8TCEuPXGXBO Cl5P5B8OYYnkHkGWutAVlUTV8KESOIm/KJIA7jJA+Ss9VhMjtePfgWexw+P8itFRSRrrwyUf E+0WcAevblUi45LjWWZgpg3A80tHP0iToOZ5MbdYk7YFBE29cDSleskfV80ZKxFv6koQocq0 vXzTfHvXNDELAuH7Ms/WJcdUzmPyBf3Oq6mKBBH8J6XZc9LjjNZwNbyvsHSrV5bgmu/THX2n g/3be+iqf6OggCiy3I1NSMJ5KtR0q2H2Nx2Vqb1fYPOID8McMV9Ll6rh8S8AEQEAAcLAfAQY AQgAJgIbDBYhBC3fcuWlpVuonapC4cI9kfOhJf6oBQJnEXWBBQkQ/lrSAAoJEMI9kfOhJf6o cakH+QHwDszsoYvmrNq36MFGgvAHRjdlrHRBa4A1V1kzd4kOUokongcrOOgHY9yfglcvZqlJ qfa4l+1oxs1BvCi29psteQTtw+memmcGruKi+YHD7793zNCMtAtYidDmQ2pWaLfqSaryjlzR /3tBWMyvIeWZKURnZbBzWRREB7iWxEbZ014B3gICqZPDRwwitHpH8Om3eZr7ygZck6bBa4MU o1XgbZcspyCGqu1xF/bMAY2iCDcq6ULKQceuKkbeQ8qxvt9hVxJC2W3lHq8dlK1pkHPDg9wO JoAXek8MF37R8gpLoGWl41FIUb3hFiu3zhDDvslYM4BmzI18QgQTQnotJH8= In-Reply-To: <20260131013438.286422-1-inwardvessel@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 在 2026/1/31 12:04, JP Kobryn 写道: > Users of filemap_lock_folio() need to guard against the situation where > release_folio() has been invoked during reclaim but the folio was > ultimately not removed from the page cache. This patch covers one location > which may have been overlooked. > > After acquiring the folio, use set_folio_extent_mapped() to ensure the > folio private state is valid. This is especially important in the subpage > case, where the private field is an allocated struct containing bitmap and > lock data. > > Failing calls (with -ENOMEM) are treated as transient errors and execution > will follow the existing "try again" path. > > Signed-off-by: JP Kobryn > --- > fs/btrfs/extent_io.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c > index 3df399dc8856..573b29f62bc1 100644 > --- a/fs/btrfs/extent_io.c > +++ b/fs/btrfs/extent_io.c > @@ -332,6 +332,18 @@ static noinline int lock_delalloc_folios(struct inode *inode, > folio_unlock(folio); > goto out; > } > + > + /* > + * release_folio() could have cleared the folio private data > + * while we were not holding the lock. > + * Reset the mapping if needed so subpage operations can access > + * a valid private folio state. > + */ > + if (set_folio_extent_mapped(folio)) { > + folio_unlock(folio); > + goto out; > + } If the folio is released meaning it will not have dirty flag. Then the above folio_test_dirty() should be triggered and exit with -EAGAIN. We will re-search the extent io tree to re-grab a proper delalloc range. And if the folio is still dirty, it means it must still have private set. Thus I'm afraid this check is a little over-killed. Thanks, Qu > + > range_start = max_t(u64, folio_pos(folio), start); > range_len = min_t(u64, folio_next_pos(folio), end + 1) - range_start; > btrfs_folio_set_lock(fs_info, folio, range_start, range_len);