Re: [f2fs-dev] [PATCH 1/2 v4] f2fs: support large folio for immutable non-compressed case

[Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

On 12/2/25 10:38, Jaegeuk Kim wrote:
> This patch enables large folio for limited case where we can get the high-order
> memory allocation. It supports the encrypted and fsverity files, which are
> essential for Android environment.
> 
> How to test:
> - dd if=/dev/zero of=/mnt/test/test bs=1G count=4
> - f2fs_io setflags immutable /mnt/test/test
> - echo 3 > /proc/sys/vm/drop_caches
>  : to reload inode with large folio
> - f2fs_io read 32 0 1024 mmap 0 0 /mnt/test/test
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  Change log from v3:
>   - enhance the doc
> 
>  Change log from v2:
>   - add a doc
> 
>  Change log from v1:
>   - return error when trying open an inode having large folio
> 
>  Documentation/filesystems/f2fs.rst |  43 +++++
>  fs/f2fs/data.c                     | 247 +++++++++++++++++++++++++++--
>  fs/f2fs/f2fs.h                     |  16 ++
>  fs/f2fs/file.c                     |   4 +
>  fs/f2fs/inode.c                    |   6 +-
>  5 files changed, 306 insertions(+), 10 deletions(-)
> 
> diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst
> index cb90d1ae82d0..9b3b835a174e 100644
> --- a/Documentation/filesystems/f2fs.rst
> +++ b/Documentation/filesystems/f2fs.rst
> @@ -1033,3 +1033,46 @@ the reserved space back to F2FS for its own use.
>  So, the key idea is, user can do any file operations on /dev/vdc, and
>  reclaim the space after the use, while the space is counted as /data.
>  That doesn't require modifying partition size and filesystem format.
> +
> +Per-file Read-Only Large Folio Support
> +--------------------------------------
> +
> +F2FS implements large folio support on the read path to leverage high-order
> +page allocation for significant performance gains. To minimize code complexity,
> +this support is currently excluded from the write path, which requires handling
> +complex optimizations such as compression and block allocation modes.
> +
> +This optional feature is triggered only when a file's immutable bit is set.
> +Consequently, F2FS will return EOPNOTSUPP if a user attempts to open a cached
> +file with write permissions, even immediately after clearing the bit. Write
> +access is only restored once the cached inode is dropped. The usage flow is
> +demonstrated below:
> +
> +.. code-block::
> +
> +   # f2fs_io setflags immutable /data/testfile_read_seq
> +
> +   /* flush and reload the inode to enable the large folio */
> +   # sync && echo 3 > /proc/sys/vm/drop_caches
> +
> +   /* mmap(MAP_POPULATE) + mlock() */
> +   # f2fs_io read 128 0 1024 mmap 1 0 /data/testfile_read_seq
> +
> +   /* mmap() + fadvise(POSIX_FADV_WILLNEED) + mlock() */
> +   # f2fs_io read 128 0 1024 fadvise 1 0 /data/testfile_read_seq
> +
> +   /* mmap() + mlock2(MLOCK_ONFAULT) + madvise(MADV_POPULATE_READ) */
> +   # f2fs_io read 128 0 1024 madvise 1 0 /data/testfile_read_seq
> +
> +   # f2fs_io clearflags immutable /data/testfile_read_seq
> +
> +   # f2fs_io write 1 0 1 zero buffered /data/testfile_read_seq
> +   Failed to open /mnt/test/test: Operation not supported
> +
> +   /* flush and reload the inode to disable the large folio */
> +   # sync && echo 3 > /proc/sys/vm/drop_caches
> +
> +   # f2fs_io write 1 0 1 zero buffered /data/testfile_read_seq
> +   Written 4096 bytes with pattern = zero, total_time = 29 us, max_latency = 28 us
> +
> +   # rm /data/testfile_read_seq
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 48c20386f031..acc4ef511bfb 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -31,9 +31,15 @@
>  
>  static struct kmem_cache *bio_post_read_ctx_cache;
>  static struct kmem_cache *bio_entry_slab;
> +static struct kmem_cache *ffs_entry_slab;
>  static mempool_t *bio_post_read_ctx_pool;
>  static struct bio_set f2fs_bioset;
>  
> +struct f2fs_folio_state {
> +	spinlock_t		state_lock;
> +	unsigned int		read_pages_pending;
> +};
> +
>  #define	F2FS_BIO_POOL_SIZE	NR_CURSEG_TYPE
>  
>  int __init f2fs_init_bioset(void)
> @@ -138,11 +144,15 @@ static void f2fs_finish_read_bio(struct bio *bio, bool in_task)
>  {
>  	struct folio_iter fi;
>  	struct bio_post_read_ctx *ctx = bio->bi_private;
> +	unsigned long flags;
>  
>  	bio_for_each_folio_all(fi, bio) {
>  		struct folio *folio = fi.folio;
> +		unsigned nr_pages = fi.length >> PAGE_SHIFT;
> +		bool finished = true;
>  
> -		if (f2fs_is_compressed_page(folio)) {
> +		if (!folio_test_large(folio) &&
> +		    f2fs_is_compressed_page(folio)) {
>  			if (ctx && !ctx->decompression_attempted)
>  				f2fs_end_read_compressed_page(folio, true, 0,
>  							in_task);
> @@ -156,8 +166,20 @@ static void f2fs_finish_read_bio(struct bio *bio, bool in_task)
>  				bio->bi_status = BLK_STS_IOERR;
>  		}
>  
> -		dec_page_count(F2FS_F_SB(folio), __read_io_type(folio));
> -		folio_end_read(folio, bio->bi_status == BLK_STS_OK);
> +		if (folio_test_large(folio)) {
> +			struct f2fs_folio_state *ffs = folio->private;
> +
> +			spin_lock_irqsave(&ffs->state_lock, flags);
> +			ffs->read_pages_pending -= nr_pages;
> +			finished = !ffs->read_pages_pending;
> +			spin_unlock_irqrestore(&ffs->state_lock, flags);
> +		}
> +
> +		while (nr_pages--)
> +			dec_page_count(F2FS_F_SB(folio), __read_io_type(folio));
> +
> +		if (finished)
> +			folio_end_read(folio, bio->bi_status == BLK_STS_OK);
>  	}
>  
>  	if (ctx)
> @@ -518,6 +540,9 @@ static bool f2fs_crypt_mergeable_bio(struct bio *bio, const struct inode *inode,
>  void f2fs_submit_read_bio(struct f2fs_sb_info *sbi, struct bio *bio,
>  				 enum page_type type)
>  {
> +	if (!bio)
> +		return;
> +
>  	WARN_ON_ONCE(!is_read_io(bio_op(bio)));
>  	trace_f2fs_submit_read_bio(sbi->sb, type, bio);
>  
> @@ -1209,11 +1234,21 @@ struct folio *f2fs_get_read_data_folio(struct inode *inode, pgoff_t index,
>  	struct dnode_of_data dn;
>  	struct folio *folio;
>  	int err;
> -
> +retry:
>  	folio = f2fs_grab_cache_folio(mapping, index, for_write);
>  	if (IS_ERR(folio))
>  		return folio;
>  
> +	if (folio_test_large(folio)) {
> +		pgoff_t folio_index = mapping_align_index(mapping, index);
> +
> +		f2fs_folio_put(folio, true);
> +		invalidate_inode_pages2_range(mapping, folio_index,
> +				folio_index + folio_nr_pages(folio) - 1);
> +		f2fs_schedule_timeout(DEFAULT_SCHEDULE_TIMEOUT);
> +		goto retry;
> +	}
> +
>  	if (f2fs_lookup_read_extent_cache_block(inode, index,
>  						&dn.data_blkaddr)) {
>  		if (!f2fs_is_valid_blkaddr(F2FS_I_SB(inode), dn.data_blkaddr,
> @@ -2341,6 +2376,179 @@ int f2fs_read_multi_pages(struct compress_ctx *cc, struct bio **bio_ret,
>  }
>  #endif
>  
> +static struct f2fs_folio_state *ffs_find_or_alloc(struct folio *folio)
> +{
> +	struct f2fs_folio_state *ffs = folio->private;
> +
> +	if (ffs)
> +		return ffs;
> +
> +	ffs = f2fs_kmem_cache_alloc(ffs_entry_slab, GFP_NOIO, true, NULL);
> +
> +	spin_lock_init(&ffs->state_lock);
> +	folio_attach_private(folio, ffs);
> +	return ffs;
> +}
> +
> +static void ffs_detach_free(struct folio *folio)
> +{
> +	struct f2fs_folio_state *ffs;
> +
> +	if (!folio_test_large(folio)) {
> +		folio_detach_private(folio);
> +		return;
> +	}
> +
> +	ffs = folio_detach_private(folio);
> +	if (!ffs)
> +		return;
> +
> +	WARN_ON_ONCE(ffs->read_pages_pending != 0);
> +	kmem_cache_free(ffs_entry_slab, ffs);
> +}
> +
> +static int f2fs_read_data_large_folio(struct inode *inode,
> +		struct readahead_control *rac, struct folio *folio)
> +{
> +	struct bio *bio = NULL;
> +	sector_t last_block_in_bio = 0;
> +	struct f2fs_map_blocks map = {0, };
> +	pgoff_t index, offset;
> +	unsigned max_nr_pages = rac ? readahead_count(rac) :
> +				folio_nr_pages(folio);
> +	unsigned nrpages;
> +	struct f2fs_folio_state *ffs;
> +	int ret = 0;
> +
> +	if (!IS_IMMUTABLE(inode))
> +		return -EOPNOTSUPP;
> +
> +	if (f2fs_compressed_file(inode))
> +		return -EOPNOTSUPP;
> +
> +	map.m_seg_type = NO_CHECK_TYPE;
> +
> +	if (rac)
> +		folio = readahead_folio(rac);
> +next_folio:
> +	if (!folio)
> +		goto out;
> +
> +	index = folio->index;
> +	offset = 0;
> +	ffs = NULL;
> +	nrpages = folio_nr_pages(folio);
> +
> +	for (; nrpages; nrpages--) {
> +		sector_t block_nr;
> +		/*
> +		 * Map blocks using the previous result first.
> +		 */
> +		if ((map.m_flags & F2FS_MAP_MAPPED) &&
> +				index > map.m_lblk &&
> +				index < (map.m_lblk + map.m_len))
> +			goto got_it;
> +
> +		/*
> +		 * Then do more f2fs_map_blocks() calls until we are
> +		 * done with this page.
> +		 */
> +		memset(&map, 0, sizeof(map));
> +		map.m_seg_type = NO_CHECK_TYPE;
> +		map.m_lblk = index;
> +		map.m_len = max_nr_pages;
> +
> +		ret = f2fs_map_blocks(inode, &map, F2FS_GET_BLOCK_DEFAULT);
> +		if (ret)
> +			goto err_out;
> +got_it:
> +		if ((map.m_flags & F2FS_MAP_MAPPED)) {
> +			block_nr = map.m_pblk + index - map.m_lblk;
> +			if (!f2fs_is_valid_blkaddr(F2FS_I_SB(inode), block_nr,
> +						DATA_GENERIC_ENHANCE_READ)) {
> +				ret = -EFSCORRUPTED;
> +				goto err_out;
> +			}
> +		} else {
> +			folio_zero_range(folio, offset << PAGE_SHIFT, PAGE_SIZE);
> +			if (f2fs_need_verity(inode, index) &&
> +			    !fsverity_verify_page(folio_file_page(folio,
> +								index))) {
> +				ret = -EIO;
> +				goto err_out;
> +			}
> +			continue;
> +		}
> +
> +		/*
> +		 * This page will go to BIO.  Do we need to send this
> +		 * BIO off first?
> +		 */
> +		if (bio && (!page_is_mergeable(F2FS_I_SB(inode), bio,
> +						last_block_in_bio, block_nr) ||
> +			!f2fs_crypt_mergeable_bio(bio, inode, index, NULL))) {
> +submit_and_realloc:
> +			f2fs_submit_read_bio(F2FS_I_SB(inode), bio, DATA);
> +			bio = NULL;
> +		}
> +		if (bio == NULL)
> +			bio = f2fs_grab_read_bio(inode, block_nr,
> +					max_nr_pages,
> +					f2fs_ra_op_flags(rac),
> +					index, false);
> +
> +		/*
> +		 * If the page is under writeback, we need to wait for
> +		 * its completion to see the correct decrypted data.
> +		 */
> +		f2fs_wait_on_block_writeback(inode, block_nr);
> +
> +		if (!bio_add_folio(bio, folio, F2FS_BLKSIZE,
> +					offset << PAGE_SHIFT))

What do you think of adding physical contiguous folio in batch? I guess we can
reduce loop number of calling several functions here?

Thanks,

> +			goto submit_and_realloc;
> +
> +		if (folio_test_large(folio)) {
> +			ffs = ffs_find_or_alloc(folio);
> +
> +			/* set the bitmap to wait */
> +			spin_lock_irq(&ffs->state_lock);
> +			ffs->read_pages_pending++;
> +			spin_unlock_irq(&ffs->state_lock);
> +		}
> +
> +		inc_page_count(F2FS_I_SB(inode), F2FS_RD_DATA);
> +		f2fs_update_iostat(F2FS_I_SB(inode), NULL, FS_DATA_READ_IO,
> +				F2FS_BLKSIZE);
> +		last_block_in_bio = block_nr;
> +		index++;
> +		offset++;
> +	}
> +	if (rac) {
> +		folio = readahead_folio(rac);
> +		goto next_folio;
> +	}
> +err_out:
> +	/* Nothing was submitted. */
> +	if (!bio) {
> +		if (!ret)
> +			folio_mark_uptodate(folio);
> +		folio_unlock(folio);
> +		return ret;
> +	}
> +
> +	if (ret) {
> +		f2fs_submit_read_bio(F2FS_I_SB(inode), bio, DATA);
> +
> +		/* Wait bios and clear uptodate. */
> +		folio_lock(folio);
> +		folio_clear_uptodate(folio);
> +		folio_unlock(folio);
> +	}
> +out:
> +	f2fs_submit_read_bio(F2FS_I_SB(inode), bio, DATA);
> +	return ret;
> +}
> +
>  /*
>   * This function was originally taken from fs/mpage.c, and customized for f2fs.
>   * Major change was from block_size == page_size in f2fs by default.
> @@ -2366,9 +2574,13 @@ static int f2fs_mpage_readpages(struct inode *inode,
>  	pgoff_t index;
>  #endif
>  	unsigned nr_pages = rac ? readahead_count(rac) : 1;
> +	struct address_space *mapping = rac ? rac->mapping : folio->mapping;
>  	unsigned max_nr_pages = nr_pages;
>  	int ret = 0;
>  
> +	if (mapping_large_folio_support(mapping))
> +		return f2fs_read_data_large_folio(inode, rac, folio);
> +
>  #ifdef CONFIG_F2FS_FS_COMPRESSION
>  	if (f2fs_compressed_file(inode)) {
>  		index = rac ? readahead_index(rac) : folio->index;
> @@ -2459,8 +2671,7 @@ static int f2fs_mpage_readpages(struct inode *inode,
>  		}
>  #endif
>  	}
> -	if (bio)
> -		f2fs_submit_read_bio(F2FS_I_SB(inode), bio, DATA);
> +	f2fs_submit_read_bio(F2FS_I_SB(inode), bio, DATA);
>  	return ret;
>  }
>  
> @@ -3747,7 +3958,12 @@ void f2fs_invalidate_folio(struct folio *folio, size_t offset, size_t length)
>  			f2fs_remove_dirty_inode(inode);
>  		}
>  	}
> -	folio_detach_private(folio);
> +
> +	if (offset || length != folio_size(folio))
> +		return;
> +
> +	folio_cancel_dirty(folio);
> +	ffs_detach_free(folio);
>  }
>  
>  bool f2fs_release_folio(struct folio *folio, gfp_t wait)
> @@ -3756,7 +3972,7 @@ bool f2fs_release_folio(struct folio *folio, gfp_t wait)
>  	if (folio_test_dirty(folio))
>  		return false;
>  
> -	folio_detach_private(folio);
> +	ffs_detach_free(folio);
>  	return true;
>  }
>  
> @@ -4162,12 +4378,25 @@ int __init f2fs_init_bio_entry_cache(void)
>  {
>  	bio_entry_slab = f2fs_kmem_cache_create("f2fs_bio_entry_slab",
>  			sizeof(struct bio_entry));
> -	return bio_entry_slab ? 0 : -ENOMEM;
> +
> +	if (!bio_entry_slab)
> +		return -ENOMEM;
> +
> +	ffs_entry_slab = f2fs_kmem_cache_create("f2fs_ffs_slab",
> +			sizeof(struct f2fs_folio_state));
> +
> +	if (!ffs_entry_slab) {
> +		kmem_cache_destroy(bio_entry_slab);
> +		return -ENOMEM;
> +	}
> +
> +	return 0;
>  }
>  
>  void f2fs_destroy_bio_entry_cache(void)
>  {
>  	kmem_cache_destroy(bio_entry_slab);
> +	kmem_cache_destroy(ffs_entry_slab);
>  }
>  
>  static int f2fs_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 86785068554f..d7600979218e 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -4928,6 +4928,22 @@ static inline bool is_journalled_quota(struct f2fs_sb_info *sbi)
>  	return false;
>  }
>  
> +static inline bool f2fs_quota_file(struct inode *inode)
> +{
> +#ifdef CONFIG_QUOTA
> +	int i;
> +
> +	if (!f2fs_sb_has_quota_ino(F2FS_I_SB(inode)))
> +		return false;
> +
> +	for (i = 0; i < MAXQUOTAS; i++) {
> +		if (f2fs_qf_ino(F2FS_I_SB(inode)->sb, i) == inode->i_ino)
> +			return true;
> +	}
> +#endif
> +	return false;
> +}
> +
>  static inline bool f2fs_block_unit_discard(struct f2fs_sb_info *sbi)
>  {
>  	return F2FS_OPTION(sbi).discard_unit == DISCARD_UNIT_BLOCK;
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index d7047ca6b98d..e75e61ac50d7 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -624,6 +624,10 @@ static int f2fs_file_open(struct inode *inode, struct file *filp)
>  	if (!f2fs_is_compress_backend_ready(inode))
>  		return -EOPNOTSUPP;
>  
> +	if (mapping_large_folio_support(inode->i_mapping) &&
> +	    filp->f_mode & FMODE_WRITE)
> +		return -EOPNOTSUPP;
> +
>  	err = fsverity_file_open(inode, filp);
>  	if (err)
>  		return err;
> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
> index e2405b79b3cc..9162154d5211 100644
> --- a/fs/f2fs/inode.c
> +++ b/fs/f2fs/inode.c
> @@ -597,6 +597,8 @@ struct inode *f2fs_iget(struct super_block *sb, unsigned long ino)
>  	if (ret)
>  		goto bad_inode;
>  make_now:
> +	f2fs_set_inode_flags(inode);
> +
>  	if (ino == F2FS_NODE_INO(sbi)) {
>  		inode->i_mapping->a_ops = &f2fs_node_aops;
>  		mapping_set_gfp_mask(inode->i_mapping, GFP_NOFS);
> @@ -618,6 +620,9 @@ struct inode *f2fs_iget(struct super_block *sb, unsigned long ino)
>  		inode->i_op = &f2fs_file_inode_operations;
>  		inode->i_fop = &f2fs_file_operations;
>  		inode->i_mapping->a_ops = &f2fs_dblock_aops;
> +		if (IS_IMMUTABLE(inode) && !f2fs_compressed_file(inode) &&
> +		    !f2fs_quota_file(inode))
> +			mapping_set_folio_min_order(inode->i_mapping, 0);
>  	} else if (S_ISDIR(inode->i_mode)) {
>  		inode->i_op = &f2fs_dir_inode_operations;
>  		inode->i_fop = &f2fs_dir_operations;
> @@ -638,7 +643,6 @@ struct inode *f2fs_iget(struct super_block *sb, unsigned long ino)
>  		ret = -EIO;
>  		goto bad_inode;
>  	}
> -	f2fs_set_inode_flags(inode);
>  
>  	unlock_new_inode(inode);
>  	trace_f2fs_iget(inode);



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