Merge tag 'f2fs-for-6.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs

Pull f2fs updates from Jaegeuk Kim:
 "This focuses on two primary updates for Android devices.

  First, it sets hash-based file name lookup as the default method to
  improve performance, while retaining an option to fall back to a
  linear lookup.

  Second, it resolves a persistent issue with the 'checkpoint=enable'
  feature.

  The update further boosts performance by prefetching node blocks,
  merging FUA writes more efficiently, and optimizing block allocation
  policies.

  The release is rounded out by a comprehensive set of bug fixes that
  address memory safety, data integrity, and potential system hangs,
  along with minor documentation and code clean-ups.

  Enhancements:
   - add mount option and sysfs entry to tune the lookup mode
   - dump more information and add a timeout when enabling/disabling
     checkpoints
   - readahead node blocks in F2FS_GET_BLOCK_PRECACHE mode
   - merge FUA command with the existing writes
   - allocate HOT_DATA for IPU writes
   - Use allocate_section_policy to control write priority in
     multi-devices setups
   - add reserved nodes for privileged users
   - Add bggc_io_aware to adjust the priority of BG_GC when issuing IO
   - show the list of donation files

  Bug fixes:
   - add missing dput() when printing the donation list
   - fix UAF issue in f2fs_merge_page_bio()
   - add sanity check on ei.len in __update_extent_tree_range()
   - fix infinite loop in __insert_extent_tree()
   - fix zero-sized extent for precache extents
   - fix to mitigate overhead of f2fs_zero_post_eof_page()
   - fix to avoid migrating empty section
   - fix to truncate first page in error path of f2fs_truncate()
   - fix to update map->m_next_extent correctly in f2fs_map_blocks()
   - fix wrong layout information on 16KB page
   - fix to do sanity check on node footer for non inode dnode
   - fix to avoid NULL pointer dereference in
     f2fs_check_quota_consistency()
   - fix to detect potential corrupted nid in free_nid_list
   - fix to clear unusable_cap for checkpoint=enable
   - fix to zero data after EOF for compressed file correctly
   - fix to avoid overflow while left shift operation
   - fix condition in __allow_reserved_blocks()"

* tag 'f2fs-for-6.18-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jaegeuk/f2fs: (43 commits)
  f2fs: add missing dput() when printing the donation list
  f2fs: fix UAF issue in f2fs_merge_page_bio()
  f2fs: readahead node blocks in F2FS_GET_BLOCK_PRECACHE mode
  f2fs: add sanity check on ei.len in __update_extent_tree_range()
  f2fs: fix infinite loop in __insert_extent_tree()
  f2fs: fix zero-sized extent for precache extents
  f2fs: fix to mitigate overhead of f2fs_zero_post_eof_page()
  f2fs: fix to avoid migrating empty section
  f2fs: fix to truncate first page in error path of f2fs_truncate()
  f2fs: fix to update map->m_next_extent correctly in f2fs_map_blocks()
  f2fs: fix wrong layout information on 16KB page
  f2fs: clean up error handing of f2fs_submit_page_read()
  f2fs: avoid unnecessary folio_clear_uptodate() for cleanup
  f2fs: merge FUA command with the existing writes
  f2fs: allocate HOT_DATA for IPU writes
  f2fs: Use allocate_section_policy to control write priority in multi-devices setups
  Documentation: f2fs: Reword title
  Documentation: f2fs: Indent compression_mode option list
  Documentation: f2fs: Wrap snippets in literal code blocks
  Documentation: f2fs: Span write hint table section rows
  ...

Author: torvalds

Documentation/ABI/testing/sysfs-fs-f2fs

@@ -822,8 +822,8 @@ What:		/sys/fs/f2fs/<disk>/gc_valid_thresh_ratio
 Date:		September 2024
 Contact:	"Daeho Jeong" <[email protected]>
 Description:	It controls the valid block ratio threshold not to trigger excessive GC
-		for zoned deivces. The initial value of it is 95(%). F2FS will stop the
-		background GC thread from intiating GC for sections having valid blocks
+		for zoned devices. The initial value of it is 95(%). F2FS will stop the
+		background GC thread from initiating GC for sections having valid blocks
 		exceeding the ratio.
 
 What:		/sys/fs/f2fs/<disk>/max_read_extent_count
@@ -847,7 +847,7 @@ Description:	For several zoned storage devices, vendors will provide extra space
 		filesystem level GC. To do that, we can reserve the space using
 		reserved_blocks. However, it is not enough, since this extra space should
 		not be shown to users. So, with this new sysfs node, we can hide the space
-		by substracting reserved_blocks from total bytes.
+		by subtracting reserved_blocks from total bytes.
 
 What:		/sys/fs/f2fs/<disk>/encoding_flags
 Date:		April 2025
@@ -883,3 +883,53 @@ Date:		June 2025
 Contact:	"Daeho Jeong" <[email protected]>
 Description:	Control GC algorithm for boost GC. 0: cost benefit, 1: greedy
 		Default: 1
+
+What:		/sys/fs/f2fs/<disk>/effective_lookup_mode
+Date:		August 2025
+Contact:	"Daniel Lee" <[email protected]>
+Description:
+		This is a read-only entry to show the effective directory lookup mode
+		F2FS is currently using for casefolded directories.
+		This considers both the "lookup_mode" mount option and the on-disk
+		encoding flag, SB_ENC_NO_COMPAT_FALLBACK_FL.
+
+		Possible values are:
+		- "perf": Hash-only lookup.
+		- "compat": Hash-based lookup with a linear search fallback enabled
+		- "auto:perf": lookup_mode is auto and fallback is disabled on-disk
+		- "auto:compat": lookup_mode is auto and fallback is enabled on-disk
+
+What:		/sys/fs/f2fs/<disk>/bggc_io_aware
+Date:		August 2025
+Contact:	"Liao Yuanhong" <[email protected]>
+Description:	Used to adjust the BG_GC priority when pending IO, with a default value
+		of 0. Specifically, for ZUFS, the default value is 1.
+
+		==================  ======================================================
+		value				description
+		bggc_io_aware = 0   skip background GC if there is any kind of pending IO
+		bggc_io_aware = 1   skip background GC if there is pending read IO
+		bggc_io_aware = 2   don't aware IO for background GC
+		==================  ======================================================
+
+What:		/sys/fs/f2fs/<disk>/allocate_section_hint
+Date:		August 2025
+Contact:	"Liao Yuanhong" <[email protected]>
+Description:	Indicates the hint section between the first device and others in multi-devices
+		setup. It defaults to the end of the first device in sections. For a single storage
+		device, it defaults to the total number of sections. It can be manually set to match
+		scenarios where multi-devices are mapped to the same dm device.
+
+What:		/sys/fs/f2fs/<disk>/allocate_section_policy
+Date:		August 2025
+Contact:	"Liao Yuanhong" <[email protected]>
+Description:	Controls write priority in multi-devices setups. A value of 0 means normal writing.
+		A value of 1 prioritizes writing to devices before the allocate_section_hint. A value of 2
+		prioritizes writing to devices after the allocate_section_hint. The default is 0.
+
+		===========================  ==========================================================
+		value					     description
+		allocate_section_policy = 0  Normal writing
+		allocate_section_policy = 1  Prioritize writing to section before allocate_section_hint
+		allocate_section_policy = 2  Prioritize writing to section after allocate_section_hint
+		===========================  ==========================================================

Documentation/filesystems/f2fs.rst

@@ -1,8 +1,11 @@
 .. SPDX-License-Identifier: GPL-2.0
 
-==========================================
-WHAT IS Flash-Friendly File System (F2FS)?
-==========================================
+=================================
+Flash-Friendly File System (F2FS)
+=================================
+
+Overview
+========
 
 NAND flash memory-based storage devices, such as SSD, eMMC, and SD cards, have
 been equipped on a variety systems ranging from mobile to server systems. Since
@@ -173,9 +176,12 @@ data_flush		 Enable data flushing before checkpoint in order to
 			 persist data of regular and symlink.
 reserve_root=%d		 Support configuring reserved space which is used for
 			 allocation from a privileged user with specified uid or
-			 gid, unit: 4KB, the default limit is 0.2% of user blocks.
-resuid=%d		 The user ID which may use the reserved blocks.
-resgid=%d		 The group ID which may use the reserved blocks.
+			 gid, unit: 4KB, the default limit is 12.5% of user blocks.
+reserve_node=%d		 Support configuring reserved nodes which are used for
+			 allocation from a privileged user with specified uid or
+			 gid, the default limit is 12.5% of all nodes.
+resuid=%d		 The user ID which may use the reserved blocks and nodes.
+resgid=%d		 The group ID which may use the reserved blocks and nodes.
 fault_injection=%d	 Enable fault injection in all supported types with
 			 specified injection rate.
 fault_type=%d		 Support configuring fault injection type, should be
@@ -291,9 +297,13 @@ compress_algorithm=%s	 Control compress algorithm, currently f2fs supports "lzo"
 			 "lz4", "zstd" and "lzo-rle" algorithm.
 compress_algorithm=%s:%d Control compress algorithm and its compress level, now, only
 			 "lz4" and "zstd" support compress level config.
+
+                         =========      ===========
 			 algorithm	level range
+                         =========      ===========
 			 lz4		3 - 16
 			 zstd		1 - 22
+                         =========      ===========
 compress_log_size=%u	 Support configuring compress cluster size. The size will
 			 be 4KB * (1 << %u). The default and minimum sizes are 16KB.
 compress_extension=%s	 Support adding specified extension, so that f2fs can enable
@@ -357,6 +367,7 @@ errors=%s		 Specify f2fs behavior on critical errors. This supports modes:
 			 panic immediately, continue without doing anything, and remount
 			 the partition in read-only mode. By default it uses "continue"
 			 mode.
+
 			 ====================== =============== =============== ========
 			 mode			continue	remount-ro	panic
 			 ====================== =============== =============== ========
@@ -370,6 +381,25 @@ errors=%s		 Specify f2fs behavior on critical errors. This supports modes:
 			 ====================== =============== =============== ========
 nat_bits		 Enable nat_bits feature to enhance full/empty nat blocks access,
 			 by default it's disabled.
+lookup_mode=%s		 Control the directory lookup behavior for casefolded
+			 directories. This option has no effect on directories
+			 that do not have the casefold feature enabled.
+
+			 ================== ========================================
+			 Value		    Description
+			 ================== ========================================
+			 perf		    (Default) Enforces a hash-only lookup.
+					    The linear search fallback is always
+					    disabled, ignoring the on-disk flag.
+			 compat		    Enables the linear search fallback for
+					    compatibility with directory entries
+					    created by older kernel that used a
+					    different case-folding algorithm.
+					    This mode ignores the on-disk flag.
+			 auto		    F2FS determines the mode based on the
+					    on-disk `SB_ENC_NO_COMPAT_FALLBACK_FL`
+					    flag.
+			 ================== ========================================
 ======================== ============================================================
 
 Debugfs Entries
@@ -795,11 +825,13 @@ ioctl(COLD)           COLD_DATA                WRITE_LIFE_EXTREME
 extension list        "                        "
 
 -- buffered io
+------------------------------------------------------------------
 N/A                   COLD_DATA                WRITE_LIFE_EXTREME
 N/A                   HOT_DATA                 WRITE_LIFE_SHORT
 N/A                   WARM_DATA                WRITE_LIFE_NOT_SET
 
 -- direct io
+------------------------------------------------------------------
 WRITE_LIFE_EXTREME    COLD_DATA                WRITE_LIFE_EXTREME
 WRITE_LIFE_SHORT      HOT_DATA                 WRITE_LIFE_SHORT
 WRITE_LIFE_NOT_SET    WARM_DATA                WRITE_LIFE_NOT_SET
@@ -915,24 +947,26 @@ compression enabled files (refer to "Compression implementation" section for how
 enable compression on a regular inode).
 
 1) compress_mode=fs
-This is the default option. f2fs does automatic compression in the writeback of the
-compression enabled files.
+
+   This is the default option. f2fs does automatic compression in the writeback of the
+   compression enabled files.
 
 2) compress_mode=user
-This disables the automatic compression and gives the user discretion of choosing the
-target file and the timing. The user can do manual compression/decompression on the
-compression enabled files using F2FS_IOC_DECOMPRESS_FILE and F2FS_IOC_COMPRESS_FILE
-ioctls like the below.
 
-To decompress a file,
+   This disables the automatic compression and gives the user discretion of choosing the
+   target file and the timing. The user can do manual compression/decompression on the
+   compression enabled files using F2FS_IOC_DECOMPRESS_FILE and F2FS_IOC_COMPRESS_FILE
+   ioctls like the below.
+
+To decompress a file::
 
-fd = open(filename, O_WRONLY, 0);
-ret = ioctl(fd, F2FS_IOC_DECOMPRESS_FILE);
+  fd = open(filename, O_WRONLY, 0);
+  ret = ioctl(fd, F2FS_IOC_DECOMPRESS_FILE);
 
-To compress a file,
+To compress a file::
 
-fd = open(filename, O_WRONLY, 0);
-ret = ioctl(fd, F2FS_IOC_COMPRESS_FILE);
+  fd = open(filename, O_WRONLY, 0);
+  ret = ioctl(fd, F2FS_IOC_COMPRESS_FILE);
 
 NVMe Zoned Namespace devices
 ----------------------------
@@ -962,32 +996,32 @@ reserved and used by another filesystem or for different purposes. Once that
 external usage is complete, the device aliasing file can be deleted, releasing
 the reserved space back to F2FS for its own use.
 
-<use-case>
-
-# ls /dev/vd*
-/dev/vdb (32GB) /dev/vdc (32GB)
-# mkfs.ext4 /dev/vdc
-# mkfs.f2fs -c /dev/[email protected] /dev/vdb
-# mount /dev/vdb /mnt/f2fs
-# ls -l /mnt/f2fs
-vdc.file
-# df -h
-/dev/vdb                            64G   33G   32G  52% /mnt/f2fs
-
-# mount -o loop /dev/vdc /mnt/ext4
-# df -h
-/dev/vdb                            64G   33G   32G  52% /mnt/f2fs
-/dev/loop7                          32G   24K   30G   1% /mnt/ext4
-# umount /mnt/ext4
-
-# f2fs_io getflags /mnt/f2fs/vdc.file
-get a flag on /mnt/f2fs/vdc.file ret=0, flags=nocow(pinned),immutable
-# f2fs_io setflags noimmutable /mnt/f2fs/vdc.file
-get a flag on noimmutable ret=0, flags=800010
-set a flag on /mnt/f2fs/vdc.file ret=0, flags=noimmutable
-# rm /mnt/f2fs/vdc.file
-# df -h
-/dev/vdb                            64G  753M   64G   2% /mnt/f2fs
+.. code-block::
+
+   # ls /dev/vd*
+   /dev/vdb (32GB) /dev/vdc (32GB)
+   # mkfs.ext4 /dev/vdc
+   # mkfs.f2fs -c /dev/[email protected] /dev/vdb
+   # mount /dev/vdb /mnt/f2fs
+   # ls -l /mnt/f2fs
+   vdc.file
+   # df -h
+   /dev/vdb                            64G   33G   32G  52% /mnt/f2fs
+
+   # mount -o loop /dev/vdc /mnt/ext4
+   # df -h
+   /dev/vdb                            64G   33G   32G  52% /mnt/f2fs
+   /dev/loop7                          32G   24K   30G   1% /mnt/ext4
+   # umount /mnt/ext4
+
+   # f2fs_io getflags /mnt/f2fs/vdc.file
+   get a flag on /mnt/f2fs/vdc.file ret=0, flags=nocow(pinned),immutable
+   # f2fs_io setflags noimmutable /mnt/f2fs/vdc.file
+   get a flag on noimmutable ret=0, flags=800010
+   set a flag on /mnt/f2fs/vdc.file ret=0, flags=noimmutable
+   # rm /mnt/f2fs/vdc.file
+   # df -h
+   /dev/vdb                            64G  753M   64G   2% /mnt/f2fs
 
 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.