[PATCH v2 3/3] ceph: switch to 4KB block size if quota size is not aligned to 4MB

[xiubli@redhat.com]

From: Xiubo Li <xiubli@redhat.com>

If the quota size is larger than but not aligned to 4MB, the statfs
will always set the block size to 4MB and round down the fragment
size. For exmaple if the quota size is 6MB, the `df` will always
show 4MB capacity.

Make the block size to 4KB as default if quota size is set unless
the quota size is larger than or equals to 4MB and at the same time
it aligns to 4MB.

Signed-off-by: Xiubo Li <xiubli@redhat.com>
---
 fs/ceph/quota.c | 32 ++++++++++++++++++++------------
 1 file changed, 20 insertions(+), 12 deletions(-)

diff --git a/fs/ceph/quota.c b/fs/ceph/quota.c
index 64592adfe48f..37fe86bfb919 100644
--- a/fs/ceph/quota.c
+++ b/fs/ceph/quota.c
@@ -483,6 +483,7 @@ bool ceph_quota_update_statfs(struct ceph_fs_client *fsc, struct kstatfs *buf)
 	struct inode *in;
 	u64 total = 0, used, free;
 	bool is_updated = false;
+	u32 block_shift = CEPH_4K_BLOCK_SHIFT;
 
 	down_read(&mdsc->snap_rwsem);
 	realm = get_quota_realm(mdsc, d_inode(fsc->sb->s_root),
@@ -498,25 +499,32 @@ bool ceph_quota_update_statfs(struct ceph_fs_client *fsc, struct kstatfs *buf)
 		ci = ceph_inode(in);
 		spin_lock(&ci->i_ceph_lock);
 		if (ci->i_max_bytes) {
-			total = ci->i_max_bytes >> CEPH_BLOCK_SHIFT;
-			used = ci->i_rbytes >> CEPH_BLOCK_SHIFT;
-			/* For quota size less than 4MB, use 4KB block size */
-			if (!total) {
-				total = ci->i_max_bytes >> CEPH_4K_BLOCK_SHIFT;
-				used = ci->i_rbytes >> CEPH_4K_BLOCK_SHIFT;
-	                        buf->f_frsize = 1 << CEPH_4K_BLOCK_SHIFT;
-			}
-			/* It is possible for a quota to be exceeded.
+			/*
+			 * Switch to 4MB block size if quota size is
+			 * larger than or equals to 4MB and at the
+			 * same time is aligned to 4MB.
+			 */
+			if (IS_ALIGNED(ci->i_max_bytes, CEPH_BLOCK_SIZE))
+				block_shift = CEPH_BLOCK_SHIFT;
+
+			total = ci->i_max_bytes >> block_shift;
+			used = ci->i_rbytes >> block_shift;
+			buf->f_frsize = 1 << block_shift;
+
+			/*
+			 * It is possible for a quota to be exceeded.
 			 * Report 'zero' in that case
 			 */
 			free = total > used ? total - used : 0;
-			/* For quota size less than 4KB, report the
+			/*
+			 * For quota size less than 4KB, report the
 			 * total=used=4KB,free=0 when quota is full
-			 * and total=free=4KB, used=0 otherwise */
+			 * and total=free=4KB, used=0 otherwise
+			 */
 			if (!total) {
 				total = 1;
 				free = ci->i_max_bytes > ci->i_rbytes ? 1 : 0;
-	                        buf->f_frsize = 1 << CEPH_4K_BLOCK_SHIFT;
+	                        buf->f_frsize = CEPH_4K_BLOCK_SIZE;
 			}
 		}
 		spin_unlock(&ci->i_ceph_lock);
-- 
2.36.0.rc1