[PATCH 1/1] erofs: fix unused pcluster_pools for higher page sizes

[Ojaswin Mujoo <ojaswin@linux.ibm.com>]

pcluster_pool[] hardcodes {1,4,16,64,128,Z_EROFS_PCLUSTER_MAX_PAGES+1},
but the assumption of Z_EROFS_PCLUSTER_MAX_PAGES == 256 is only right
for 4k page sizes. For higher page sizes like 16k or 64k, This results
in us ending up with clusters bigger than what we will ever use, since
we only support upto 1MB of compressed data. For example, on 64k page
size we will only ever use clusters with nrpages= 1, 4 and 17.

This patch fixes the allocation for such higher pages sizes by adding
some compile time checks.

Below are the clusters created right after boot on a 64KB page size
machine

$cat /proc/slabinfo | grep pcluster | cut -d" " -f1:

Before the patch:

erofs_pcluster-1
erofs_pcluster-4
erofs_pcluster-16
erofs_pcluster-17
erofs_pcluster-64
erofs_pcluster-128


After the patch:

erofs_pcluster-1
erofs_pcluster-4
erofs_pcluster-17

Fixes: 9f6cc76e6ff0 ("erofs: introduce physical cluster slab pools")
Reported-by: Shirisha G <shirisha@linux.ibm.com>
Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
---
 fs/erofs/zdata.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 602ba8b7cc79..5c2c22ed64d0 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -128,7 +128,17 @@ struct z_erofs_pcluster_slab {
 #define _PCLP(n) { .maxpages = n }
 
 static struct z_erofs_pcluster_slab pcluster_pool[] __read_mostly = {
-	_PCLP(1), _PCLP(4), _PCLP(16), _PCLP(64), _PCLP(128),
+	_PCLP(1),
+	_PCLP(4),
+#if Z_EROFS_PCLUSTER_MAX_PAGES > 16
+	_PCLP(16),
+#endif
+#if Z_EROFS_PCLUSTER_MAX_PAGES > 64
+	_PCLP(64),
+#endif
+#if Z_EROFS_PCLUSTER_MAX_PAGES > 128
+	_PCLP(128),
+#endif
 	_PCLP(Z_EROFS_PCLUSTER_MAX_PAGES + 1)
 };
 
-- 
2.55.0