NFS doesn't have DIO alignment constraints, so have NFS respond with
accommodating DIO alignment attributes (rather than plumb in GETATTR
support for STATX_DIOALIGN and STATX_DIO_READ_ALIGN).
The most coarse-grained dio_offset_align is the most accommodating
(e.g. PAGE_SIZE, in future larger may be supported).
Now that NFS has support, NFS reexport will now handle unaligned DIO
(NFSD's NFSD_IO_DIRECT support requires the underlying filesystem
support STATX_DIOALIGN and/or STATX_DIO_READ_ALIGN).
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
---
fs/nfs/inode.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index 338ef77ae4230..7866d60b18452 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -1066,6 +1066,21 @@ int nfs_getattr(struct mnt_idmap *idmap, const struct path *path,
if (S_ISDIR(inode->i_mode))
stat->blksize = NFS_SERVER(inode)->dtsize;
stat->btime = NFS_I(inode)->btime;
+
+ /* Special handling for STATX_DIOALIGN and STATX_DIO_READ_ALIGN
+ * - NFS doesn't have DIO alignment constraints, avoid getting
+ * these DIO attrs from remote and just respond with most
+ * accommodating limits (so client will issue supported DIO).
+ * - this is unintuitive, but the most coarse-grained
+ * dio_offset_align is the most accommodating.
+ */
+ if ((request_mask & (STATX_DIOALIGN | STATX_DIO_READ_ALIGN)) &&
+ S_ISREG(inode->i_mode)) {
+ stat->result_mask |= STATX_DIOALIGN | STATX_DIO_READ_ALIGN;
+ stat->dio_mem_align = 4; /* 4-byte alignment */
+ stat->dio_offset_align = PAGE_SIZE;
+ stat->dio_read_offset_align = stat->dio_offset_align;
+ }
out:
trace_nfs_getattr_exit(inode, err);
return err;
--
2.44.0
