Merge tag 'statx-dioalign-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux

Pull STATX_DIOALIGN support from Eric Biggers:
 "Make statx() support reporting direct I/O (DIO) alignment information.

  This provides a generic interface for userspace programs to determine
  whether a file supports DIO, and if so with what alignment
  restrictions. Specifically, STATX_DIOALIGN works on block devices, and
  on regular files when their containing filesystem has implemented
  support.

  An interface like this has been requested for years, since the
  conditions for when DIO is supported in Linux have gotten increasingly
  complex over time. Today, DIO support and alignment requirements can
  be affected by various filesystem features such as multi-device
  support, data journalling, inline data, encryption, verity,
  compression, checkpoint disabling, log-structured mode, etc.

  Further complicating things, Linux v6.0 relaxed the traditional rule
  of DIO needing to be aligned to the block device's logical block size;
  now user buffers (but not file offsets) only need to be aligned to the
  DMA alignment.

  The approach of uplifting the XFS specific ioctl XFS_IOC_DIOINFO was
  discarded in favor of creating a clean new interface with statx().

  For more information, see the individual commits and the man page
  update[1]"

Link: https://lore.kernel.org/r/20220722074229.148925-1-ebiggers@kernel.org [1]

* tag 'statx-dioalign-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux:
  xfs: support STATX_DIOALIGN
  f2fs: support STATX_DIOALIGN
  f2fs: simplify f2fs_force_buffered_io()
  f2fs: move f2fs_force_buffered_io() into file.c
  ext4: support STATX_DIOALIGN
  fscrypt: change fscrypt_dio_supported() to prepare for STATX_DIOALIGN
  vfs: support STATX_DIOALIGN on block devices
  statx: add direct I/O alignment information

1 files changed, 42 insertions, 1 deletions

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index ce4905a073b3..791770507328 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -808,6 +808,29 @@ int f2fs_truncate(struct inode *inode)
 	return 0;
 }
 
+static bool f2fs_force_buffered_io(struct inode *inode, int rw)
+{
+	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
+
+	if (!fscrypt_dio_supported(inode))
+		return true;
+	if (fsverity_active(inode))
+		return true;
+	if (f2fs_compressed_file(inode))
+		return true;
+
+	/* disallow direct IO if any of devices has unaligned blksize */
+	if (f2fs_is_multi_device(sbi) && !sbi->aligned_blksize)
+		return true;
+
+	if (f2fs_lfs_mode(sbi) && rw == WRITE && F2FS_IO_ALIGNED(sbi))
+		return true;
+	if (is_sbi_flag_set(sbi, SBI_CP_DISABLED))
+		return true;
+
+	return false;
+}
+
 int f2fs_getattr(struct user_namespace *mnt_userns, const struct path *path,
 		 struct kstat *stat, u32 request_mask, unsigned int query_flags)
 {
@@ -824,6 +847,24 @@ int f2fs_getattr(struct user_namespace *mnt_userns, const struct path *path,
 		stat->btime.tv_nsec = fi->i_crtime.tv_nsec;
 	}
 
+	/*
+	 * Return the DIO alignment restrictions if requested.  We only return
+	 * this information when requested, since on encrypted files it might
+	 * take a fair bit of work to get if the file wasn't opened recently.
+	 *
+	 * f2fs sometimes supports DIO reads but not DIO writes.  STATX_DIOALIGN
+	 * cannot represent that, so in that case we report no DIO support.
+	 */
+	if ((request_mask & STATX_DIOALIGN) && S_ISREG(inode->i_mode)) {
+		unsigned int bsize = i_blocksize(inode);
+
+		stat->result_mask |= STATX_DIOALIGN;
+		if (!f2fs_force_buffered_io(inode, WRITE)) {
+			stat->dio_mem_align = bsize;
+			stat->dio_offset_align = bsize;
+		}
+	}
+
 	flags = fi->i_flags;
 	if (flags & F2FS_COMPR_FL)
 		stat->attributes |= STATX_ATTR_COMPRESSED;
@@ -4182,7 +4223,7 @@ static bool f2fs_should_use_dio(struct inode *inode, struct kiocb *iocb,
 	if (!(iocb->ki_flags & IOCB_DIRECT))
 		return false;
 
-	if (f2fs_force_buffered_io(inode, iocb, iter))
+	if (f2fs_force_buffered_io(inode, iov_iter_rw(iter)))
 		return false;
 
 	/*