linux-kernel - [PATCH 1/2] f2fs: improve readahead for POSIX_FADV

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Message-ID: <20251121014202.1969909-1-jaegeuk@kernel.org>
Date: Fri, 21 Nov 2025 01:42:01 +0000
From: Jaegeuk Kim <jaegeuk@...nel.org>
To: linux-kernel@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net
Cc: Jaegeuk Kim <jaegeuk@...nel.org>
Subject: [PATCH 1/2] f2fs: improve readahead for POSIX_FADV_WILLNEED

This patch boosts readahead for POSIX_FADV_WILLNEED.

Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
---
 fs/f2fs/data.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++
 fs/f2fs/f2fs.h |  1 +
 fs/f2fs/file.c |  9 +++++---
 3 files changed, 68 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index a0433c8a4d84..d95974d79fb3 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2710,6 +2710,67 @@ static void f2fs_readahead(struct readahead_control *rac)
 	f2fs_mpage_readpages(inode, rac, NULL);
 }
 
+int f2fs_readahead_pages(struct file *file, loff_t offset, loff_t len)
+{
+	struct inode *inode = file_inode(file);
+	struct address_space *mapping = file->f_mapping;
+	pgoff_t start_index = offset >> PAGE_SHIFT;
+	loff_t endbyte = offset + len;
+	pgoff_t end_index;
+	unsigned long nrpages;
+	unsigned long ra_pages = (16 * 1024 * 1024) / PAGE_SIZE;
+	DEFINE_READAHEAD(ractl, NULL, &file->f_ra, mapping, start_index);
+
+	if (!S_ISREG(inode->i_mode))
+		return -EOPNOTSUPP;
+
+	/* Should be read only. */
+	if (!(file->f_mode & FMODE_READ))
+		return -EBADF;
+
+	/* Do not support compressed file for large folio. */
+	if (f2fs_compressed_file(inode))
+		return -EINVAL;
+
+	if (!mapping || len < 0)
+		return -EINVAL;
+
+	if (unlikely(!mapping->a_ops->read_folio && !mapping->a_ops->readahead))
+		return -EINVAL;
+
+	/* Load extent cache at the first readahead. */
+	f2fs_precache_extents(inode);
+
+	/*
+	 * Careful about overflows. Len == 0 means "as much as possible".  Use
+	 * unsigned math because signed overflows are undefined and UBSan
+	 * complains.
+	 */
+	if (!len || endbyte > i_size_read(inode) || endbyte < len)
+		endbyte = i_size_read(inode) - 1;
+	else
+		endbyte--;		/* inclusive */
+
+	/* First and last PARTIAL page! */
+	end_index = endbyte >> PAGE_SHIFT;
+
+	if (start_index > end_index)
+		return 0;
+
+	nrpages = end_index - start_index + 1;
+
+	while (nrpages) {
+		unsigned long this_chunk = min(nrpages, ra_pages);
+
+		ractl.ra->ra_pages = this_chunk;
+
+		page_cache_sync_ra(&ractl, this_chunk << 1);
+
+		nrpages -= this_chunk;
+	}
+	return 0;
+}
+
 int f2fs_encrypt_one_page(struct f2fs_io_info *fio)
 {
 	struct inode *inode = fio_inode(fio);
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 3340db04a7c2..934287cc5624 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -4047,6 +4047,7 @@ int f2fs_init_bio_entry_cache(void);
 void f2fs_destroy_bio_entry_cache(void);
 void f2fs_submit_read_bio(struct f2fs_sb_info *sbi, struct bio *bio,
 			  enum page_type type);
+int f2fs_readahead_pages(struct file *file, loff_t offset, loff_t len);
 int f2fs_init_write_merge_io(struct f2fs_sb_info *sbi);
 void f2fs_submit_merged_write(struct f2fs_sb_info *sbi, enum page_type type);
 void f2fs_submit_merged_write_cond(struct f2fs_sb_info *sbi,
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index d7047ca6b98d..b6f71efd6d2a 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -5305,9 +5305,12 @@ static int f2fs_file_fadvise(struct file *filp, loff_t offset, loff_t len,
 		filp->f_mode &= ~FMODE_RANDOM;
 		spin_unlock(&filp->f_lock);
 		return 0;
-	} else if (advice == POSIX_FADV_WILLNEED && offset == 0) {
-		/* Load extent cache at the first readahead. */
-		f2fs_precache_extents(inode);
+	} else if (advice == POSIX_FADV_WILLNEED) {
+		if (offset == 0 && len == -1) {
+			f2fs_precache_extents(inode);
+			return 0;
+		}
+		return f2fs_readahead_pages(filp, offset, len);
 	}
 
 	err = generic_fadvise(filp, offset, len, advice);
-- 
2.52.0.487.g5c8c507ade-goog