f2fs: support STATX_DIOALIGN

Add support for STATX_DIOALIGN to f2fs, so that direct I/O alignment
restrictions are exposed to userspace in a generic way.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Acked-by: Jaegeuk Kim <jaegeuk@kernel.org>
Link: https://lore.kernel.org/r/20220827065851.135710-8-ebiggers@kernel.org

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 8e11311db21060e68a600dd8c0c8fc0cdb26762e..79177050732803eadd5e3d3bb68577b67e743ccc 100644 (file)
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -847,6 +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;