Re: [PATCH 6.9.y] erofs: avoid allocating DEFLATE streams before mounting

Gao Xiang
2024-06-04T12:33:14Z

Hi Greg,

ping? Do these backport fixes miss the 6.6, 6.8, 6.9 queues..

Thanks,
Gao XIang

On 2024/5/30 17:21, Gao Xiang wrote:
> commit 80eb4f62056d6ae709bdd0636ab96ce660f494b2 upstream.
>
> 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+
> Reviewed-by: Sandeep Dhavale <dhavale@google.com>
> Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
> Link: https://lore.kernel.org/r/20240520090106.2898681-1-hsiangkao@linux.alibaba.com
> ---
> 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,