ksmbd: set fixed sector size to FS_SECTOR_SIZE_INFORMATION

Currently ksmbd is using ->f_bsize from vfs_statfs() as sector size.
If fat/exfat is a local share, ->f_bsize is a cluster size that is too
large to be used as a sector size. Sector sizes larger than 4K cause
problem occurs when mounting an iso file through windows client.

The error message can be obtained using Mount-DiskImage command,
 the error is:
"Mount-DiskImage : The sector size of the physical disk on which the
virtual disk resides is not supported."

This patch reports fixed 4KB sector size if ->s_blocksize is bigger
than 4KB.
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/ksmbd/smb2pdu.c

@@ -11,6 +11,7 @@
 #include <linux/statfs.h>
 #include <linux/ethtool.h>
 #include <linux/falloc.h>
+#include <linux/mount.h>
 
 #include "glob.h"
 #include "smbfsctl.h"
@@ -4995,15 +4996,17 @@ static int smb2_get_info_filesystem(struct ksmbd_work *work,
 	case FS_SECTOR_SIZE_INFORMATION:
 	{
 		struct smb3_fs_ss_info *info;
+		unsigned int sector_size =
+			min_t(unsigned int, path.mnt->mnt_sb->s_blocksize, 4096);
 
 		info = (struct smb3_fs_ss_info *)(rsp->Buffer);
 
-		info->LogicalBytesPerSector = cpu_to_le32(stfs.f_bsize);
+		info->LogicalBytesPerSector = cpu_to_le32(sector_size);
 		info->PhysicalBytesPerSectorForAtomicity =
-				cpu_to_le32(stfs.f_bsize);
-		info->PhysicalBytesPerSectorForPerf = cpu_to_le32(stfs.f_bsize);
+				cpu_to_le32(sector_size);
+		info->PhysicalBytesPerSectorForPerf = cpu_to_le32(sector_size);
 		info->FSEffPhysicalBytesPerSectorForAtomicity =
-				cpu_to_le32(stfs.f_bsize);
+				cpu_to_le32(sector_size);
 		info->Flags = cpu_to_le32(SSINFO_FLAGS_ALIGNED_DEVICE |
 				    SSINFO_FLAGS_PARTITION_ALIGNED_ON_DEVICE);
 		info->ByteOffsetForSectorAlignment = 0;