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smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=RFitKNmI; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AC80E606A320 for ; Thu, 29 Oct 2026 07:12:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=RFitKNmI Received: by smtp.kernel.org (Postfix) with ESMTPSA id C54681F031E0; Thu, 29 Oct 2026 07:12:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793257956; bh=ZqIP8rHFVaUvr35xWWY1cogweghasOeeLqDOh4JkDs8=; h=Date:Cc:Subject:To:References:From:In-Reply-To; b=RFitKNmIrd6y7IrXk2BT1ELcOf0HTtHywtmUd996Emu1nybB138jKXa+4xmcGxdiO DOtKLNL8HYeGJSDqy6R5ZIVmp5bYORMxicU3xDCLKxhx5oT4Ya9Qp8IV3YL/5yW1xm /CinfMhBwOOY0YCaiax74gDhuf7rdXix8rq4y3skoTUGVWS37NOcG2KOKGwqvfTPTD Lvl0aHh5PnF7cYfQyG0xOGACTv+tUTNBOcAYgvaKyZSIOn7pCf6kH0nAvmyqJ7TGjA JTZGAvefgtZlVHmnSGUb5V5m7oYNDGZ/LEXMBcEEkmqZfeEgQ8ZhhzxD11/64O4B8d 6xhbS9X42kFuw== Message-ID: <54cbfb8a-c87e-4fea-9448-175706e22ac2@kernel.org> Date: Thu, 29 Oct 2026 15:12:32 +0800 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: chao@kernel.org, Barry Song , Juan Yescas , Daeho Jeong , Pengfei Li , Dev Jain , David Hildenbrand , linux-kernel@vger.kernel.org, Bo Zhang , Kalesh Singh , Nanzhe Zhao , Nanzhe Zhao , Ryan Roberts Subject: Re: [PATCH v8 15/15] f2fs: make compressed files compatible with large folio To: Jaegeuk Kim , Nanzhe Zhao , linux-f2fs-devel@lists.sourceforge.net References: <20261028154407.1601430-1-nzzhao.sigma@gmail.com> <20261028154407.1601430-16-nzzhao.sigma@gmail.com> Content-Language: en-US From: Chao Yu In-Reply-To: <20261028154407.1601430-16-nzzhao.sigma@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/28/26 23:44, Nanzhe Zhao wrote: > From: Nanzhe Zhao > > The compression flag is the hint indicates that the inode can be > compressed, when the inode is using large folio, we expected it keeps > using the large folio read/write paths and its data stays uncompressed > on disk until the inode is evicted and re-read > > Let f2fs_write_begin() skip the compression overwrite preparation for > such inodes and remove the compressed-file gate in > f2fs_read_data_large_folio() so the data is simply read/written as > regular blocks. > > For the same reason, reject F2FS_IOC_COMPRESS_FILE with -EOPNOTSUPP > once the inode mapping is switched to large folios. > > Signed-off-by: Nanzhe Zhao > --- > Documentation/filesystems/f2fs.rst | 10 ++++++++ > fs/f2fs/compress.c | 2 ++ > fs/f2fs/data.c | 9 ++----- > fs/f2fs/file.c | 38 ++++++++++++++++++++++++++++++ > 4 files changed, 52 insertions(+), 7 deletions(-) > > diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst > index 55798421f2c4..b79bb67ee78e 100644 > --- a/Documentation/filesystems/f2fs.rst > +++ b/Documentation/filesystems/f2fs.rst > @@ -942,6 +942,16 @@ Compression implementation > reserved via ioctl(F2FS_IOC_RESERVE_COMPRESS_BLOCKS) or the file size is > truncated to zero. > > +- Compression and large folios are not effective at the same time on a file: > + a compressed inode does not use large folios, while an inode which is > + using large folios keeps its data uncompressed on disk. If the compression > + flag is set on an inode that is already using large folios, the flag works > + as a hint until the inode is evicted: the inode keeps using the large folio > + read/write paths, f2fs_write_begin() skips the compression overwrite > + preparation, and ioctl(F2FS_IOC_COMPRESS_FILE) fails with -EOPNOTSUPP. > + Once the inode is evicted and read back, it uses order-0 folios again and > + compression is applied as usual. > + > Compress metadata layout:: > > [Dnode Structure] > diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c > index 162bd8ef822a..721b01dd0d24 100644 > --- a/fs/f2fs/compress.c > +++ b/fs/f2fs/compress.c > @@ -78,6 +78,8 @@ bool f2fs_is_compressed_page(struct folio *folio) > return false; > if (folio_test_f2fs_nonpointer(folio)) > return false; > + if (f2fs_folio_has_ffs(folio)) > + return false; > > f2fs_bug_on(F2FS_F_SB(folio), > *((u32 *)folio->private) != F2FS_COMPRESSED_PAGE_MAGIC); > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c > index cc3c9e51db9c..ab8f5b44d63a 100644 > --- a/fs/f2fs/data.c > +++ b/fs/f2fs/data.c > @@ -3288,12 +3288,6 @@ static int f2fs_read_data_large_folio(struct inode *inode, > int ret = 0; > bool folio_in_bio = false; > > - if (f2fs_compressed_file(inode)) { > - if (folio) > - folio_unlock(folio); > - return -EOPNOTSUPP; > - } > - > map.m_seg_type = NO_CHECK_TYPE; > > if (rac) > @@ -5331,7 +5325,8 @@ static int f2fs_write_begin(const struct kiocb *iocb, > } > > #ifdef CONFIG_F2FS_FS_COMPRESSION > - if (f2fs_compressed_file(inode)) { > + if (f2fs_compressed_file(inode) && > + !mapping_large_folio_support(inode->i_mapping)) { > int ret; > struct page *page; > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > index 15bea642e986..cb7a9d4227f4 100644 > --- a/fs/f2fs/file.c > +++ b/fs/f2fs/file.c > @@ -4907,6 +4907,7 @@ static int redirty_blocks(struct inode *inode, pgoff_t page_idx, int len) > struct address_space *mapping = inode->i_mapping; > struct folio *folio; > pgoff_t redirty_idx = page_idx; > + pgoff_t end_idx = page_idx + len; > int page_len = 0, ret = 0; > > filemap_invalidate_lock_shared(mapping); > @@ -4924,6 +4925,9 @@ static int redirty_blocks(struct inode *inode, pgoff_t page_idx, int len) > } while (page_len < len); > > while (redirty_idx < page_idx) { > + pgoff_t next_idx; > + size_t off, dlen; > + > folio = filemap_lock_folio(mapping, redirty_idx); > > /* It will never fail, when folio has pinned above */ > @@ -4931,6 +4935,33 @@ static int redirty_blocks(struct inode *inode, pgoff_t page_idx, int len) > > f2fs_folio_wait_writeback(folio, true, true); > > + /* > + * Only this cluster is rewritten, while a large folio can > + * cover more than one cluster, so mark the intersection of > + * the folio and [redirty_idx, end_idx). > + */ > + next_idx = min_t(pgoff_t, folio_next_index(folio), end_idx); > + off = offset_in_folio(folio, (loff_t)redirty_idx << PAGE_SHIFT); > + dlen = (size_t)(next_idx - redirty_idx) << PAGE_SHIFT; > + > + if (folio_test_large(folio)) { > + /* > + * A compressed inode can keep using large folios, in > + * which case the compression flag only works as a hint > + * until the inode is evicted. Update the subpage dirty > + * bitmap as well, otherwise f2fs_write_cache_folios() > + * finds no dirty range and skips the whole folio. > + */ > + if (!f2fs_ffs_find_or_alloc(folio)) { > + ret = -ENOMEM; > + folio_unlock(folio); > + folio_put_refs(folio, 2); > + redirty_idx = folio_next_index(folio); Jaegeuk, Nanzhe, I missed this potential UAF, please fix this. diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index 162b7f7aa6d4..3de67522beef 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -4941,16 +4941,14 @@ static int redirty_blocks(struct inode *inode, pgoff_t page_idx, int len) */ if (!f2fs_ffs_find_or_alloc(folio)) { ret = -ENOMEM; - folio_unlock(folio); - folio_put_refs(folio, 2); - redirty_idx = folio_next_index(folio); - continue; + goto next; } f2fs_ffs_mark_subrange_dirty(folio, off, dlen); } folio_mark_dirty(folio); folio_set_f2fs_gcing(folio); +next: redirty_idx = folio_next_index(folio); folio_unlock(folio); folio_put_refs(folio, 2); Thanks, > + continue; > + } > + f2fs_ffs_mark_subrange_dirty(folio, off, dlen); > + } > + > folio_mark_dirty(folio); > folio_set_f2fs_gcing(folio); > redirty_idx = folio_next_index(folio); > @@ -5037,6 +5068,13 @@ static int f2fs_ioc_compress_file(struct file *filp) > if (!(filp->f_mode & FMODE_WRITE)) > return -EBADF; > > + /* > + * The mapping is already using large folios, where the data is kept > + * uncompressed, so refuse to start compressing the file. > + */ > + if (mapping_large_folio_support(inode->i_mapping)) > + return -EOPNOTSUPP; > + > f2fs_balance_fs(sbi, true); > > ret = mnt_want_write_file(filp);