[PATCH 6.12.y] erofs: skip sufficiently large global buffers when resizing

[Sasha Levin <sashal@kernel.org>]

From: Nikhil Gurudasani <nikhilgurudasani314@gmail.com>

[ Upstream commit a7d097cf01301c5da37927c8f26123d006f0fd8a ]

z_erofs_gbuf_nrpages is advanced only after every global buffer has been
grown. If a resize fails after some buffers were enlarged, a retry
revisits those enlarged buffers.

Retrying the same size then returns -ENOMEM because alloc_pages_bulk()
has no pages to add and the unchanged return value is treated as a
failure. Retrying an intermediate size allocates a temporary pointer
array smaller than gbuf->nrpages and copies more existing pointers than
the array can hold.

Skip buffers that already satisfy the request. Once all remaining
buffers have caught up, advancing z_erofs_gbuf_nrpages again describes
the guaranteed minimum size across the pool.

Fixes: d6db47e571dc ("erofs: do not use pagepool in z_erofs_gbuf_growsize()")
Cc: stable@vger.kernel.org # 6.10+
Signed-off-by: Nikhil Gurudasani <nikhilgurudasani314@gmail.com>
Reviewed-by: Gao Xiang <xiang@kernel.org>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <xiang@kernel.org>
[ preserved the existing kcalloc() allocation instead of upstream kzalloc_objs() ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/erofs/zutil.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/erofs/zutil.c b/fs/erofs/zutil.c
index 0dd65cefce33e..af485617fd5ff 100644
--- a/fs/erofs/zutil.c
+++ b/fs/erofs/zutil.c
@@ -79,6 +79,8 @@ int z_erofs_gbuf_growsize(unsigned int nrpages)
 
 	for (i = 0; i < z_erofs_gbuf_count; ++i) {
 		gbuf = &z_erofs_gbufpool[i];
+		if (gbuf->nrpages >= nrpages)
+			continue;
 		tmp_pages = kcalloc(nrpages, sizeof(*tmp_pages), GFP_KERNEL);
 		if (!tmp_pages)
 			goto out;
-- 
2.53.0