erofs: support STATX_DIOALIGN

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

[Before]
```
./statx_test /mnt/erofs/testfile
statx(/mnt/erofs/testfile) = 0
dio mem align:0
dio offset align:0
```

[After]
```
./statx_test /mnt/erofs/testfile
statx(/mnt/erofs/testfile) = 0
dio mem align:512
dio offset align:512
```

Signed-off-by: Hongbo Li <lihongbo22@huawei.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240718083243.2485437-1-hsiangkao@linux.alibaba.com

diff --git a/fs/erofs/inode.c b/fs/erofs/inode.c
index 5f6439a63af798512f325beb4d0af112c2b252eb..43c09aae2afcd19aa01c0380f06120535c8d78c7 100644 (file)
--- a/fs/erofs/inode.c
+++ b/fs/erofs/inode.c
@@ -334,14 +334,29 @@ int erofs_getattr(struct mnt_idmap *idmap, const struct path *path,
                  unsigned int query_flags)
 {
        struct inode *const inode = d_inode(path->dentry);
+       bool compressed =
+               erofs_inode_is_data_compressed(EROFS_I(inode)->datalayout);
 
-       if (erofs_inode_is_data_compressed(EROFS_I(inode)->datalayout))
+       if (compressed)
                stat->attributes |= STATX_ATTR_COMPRESSED;
-
        stat->attributes |= STATX_ATTR_IMMUTABLE;
        stat->attributes_mask |= (STATX_ATTR_COMPRESSED |
                                  STATX_ATTR_IMMUTABLE);
 
+       /*
+        * Return the DIO alignment restrictions if requested.
+        *
+        * In EROFS, STATX_DIOALIGN is not supported in ondemand mode and
+        * compressed files, so in these cases we report no DIO support.
+        */
+       if ((request_mask & STATX_DIOALIGN) && S_ISREG(inode->i_mode)) {
+               stat->result_mask |= STATX_DIOALIGN;
+               if (!erofs_is_fscache_mode(inode->i_sb) && !compressed) {
+                       stat->dio_mem_align =
+                               bdev_logical_block_size(inode->i_sb->s_bdev);
+                       stat->dio_offset_align = stat->dio_mem_align;
+               }
+       }
        generic_fillattr(idmap, request_mask, inode, stat);
        return 0;
 }