Re: [PATCH] erofs: avoid allocating DEFLATE streams before mounting

On Mon, May 20, 2024 at 2:06 AM Gao Xiang hsiangkao@linux.alibaba.com wrote:

Currently, each DEFLATE stream takes one 32 KiB permanent internal window buffer even if there is no running instance which uses DEFLATE algorithm.

It's unexpected and wasteful on embedded devices with limited resources and servers with hundreds of CPU cores if DEFLATE is enabled but unused.

Fixes: ffa09b3bd024 ("erofs: DEFLATE compression support") Cc: stable@vger.kernel.org # 6.6+ Signed-off-by: Gao Xiang hsiangkao@linux.alibaba.com

LGTM.

Reviewed-by: Sandeep Dhavale dhavale@google.com

Thanks, Sandeep.

---

fs/erofs/decompressor_deflate.c | 55 +++++++++++++++++---------------- 1 file changed, 29 insertions(+), 26 deletions(-)

diff --git a/fs/erofs/decompressor_deflate.c b/fs/erofs/decompressor_deflate.c index 81e65c453ef0..3a3461561a3c 100644 --- a/fs/erofs/decompressor_deflate.c +++ b/fs/erofs/decompressor_deflate.c @@ -46,39 +46,15 @@ int __init z_erofs_deflate_init(void) /* by default, use # of possible CPUs instead */ if (!z_erofs_deflate_nstrms) z_erofs_deflate_nstrms = num_possible_cpus();

•   for (; z_erofs_deflate_avail_strms < z_erofs_deflate_nstrms;
  

•        ++z_erofs_deflate_avail_strms) {
  

•           struct z_erofs_deflate *strm;
  

•           strm = kzalloc(sizeof(*strm), GFP_KERNEL);
  

•           if (!strm)
  

•                   goto out_failed;
  

•           /* XXX: in-kernel zlib cannot shrink windowbits currently */
  

•           strm->z.workspace = vmalloc(zlib_inflate_workspacesize());
  

•           if (!strm->z.workspace) {
  

•                   kfree(strm);
  

•                   goto out_failed;
  

•           }
  

•           spin_lock(&z_erofs_deflate_lock);
  

•           strm->next = z_erofs_deflate_head;
  

•           z_erofs_deflate_head = strm;
  

•           spin_unlock(&z_erofs_deflate_lock);
  

•   }
    return 0;
  

-out_failed:

•   erofs_err(NULL, "failed to allocate zlib workspace");
  

•   z_erofs_deflate_exit();
  

•   return -ENOMEM;
  

}

int z_erofs_load_deflate_config(struct super_block *sb, struct erofs_super_block *dsb, void *data, int size) { struct z_erofs_deflate_cfgs *dfl = data;

•   static DEFINE_MUTEX(deflate_resize_mutex);
  

•   static bool inited;
  
    if (!dfl || size < sizeof(struct z_erofs_deflate_cfgs)) {
            erofs_err(sb, "invalid deflate cfgs, size=%u", size);
  

@@ -89,9 +65,36 @@ int z_erofs_load_deflate_config(struct super_block *sb, erofs_err(sb, "unsupported windowbits %u", dfl->windowbits); return -EOPNOTSUPP; }

•   mutex_lock(&deflate_resize_mutex);
  

•   if (!inited) {
  

•           for (; z_erofs_deflate_avail_strms < z_erofs_deflate_nstrms;
  

•                ++z_erofs_deflate_avail_strms) {
  

•                   struct z_erofs_deflate *strm;
  

•                   strm = kzalloc(sizeof(*strm), GFP_KERNEL);
  

•                   if (!strm)
  

•                           goto failed;
  

•                   /* XXX: in-kernel zlib cannot customize windowbits */
  

•                   strm->z.workspace = vmalloc(zlib_inflate_workspacesize());
  

•                   if (!strm->z.workspace) {
  

•                           kfree(strm);
  

•                           goto failed;
  

•                   }
  
  

•                   spin_lock(&z_erofs_deflate_lock);
  

•                   strm->next = z_erofs_deflate_head;
  

•                   z_erofs_deflate_head = strm;
  

•                   spin_unlock(&z_erofs_deflate_lock);
  

•           }
  

•           inited = true;
  

•   }
  

•   mutex_unlock(&deflate_resize_mutex);
    erofs_info(sb, "EXPERIMENTAL DEFLATE feature in use. Use at your own risk!");
    return 0;
  

+failed:

•   mutex_unlock(&deflate_resize_mutex);
  

•   z_erofs_deflate_exit();
  

•   return -ENOMEM;
  

}

int z_erofs_deflate_decompress(struct z_erofs_decompress_req *rq,

2.39.3