On Fri, Dec 04, 2020 at 06:45:54PM +0300, Konstantin Komarov wrote:
> +/* external compression lzx/xpress */
> +static int decompress_lzx_xpress(struct ntfs_sb_info *sbi, const char *cmpr,
> + size_t cmpr_size, void *unc, size_t unc_size,
> + u32 frame_size)
> +{
> + int err;
> + void *ctx;
> +
> + if (cmpr_size == unc_size) {
> + /* frame not compressed */
> + memcpy(unc, cmpr, unc_size);
> + return 0;
> + }
> +
> + err = 0;
> + ctx = NULL;
> + spin_lock(&sbi->compress.lock);
> + if (frame_size == 0x8000) {
> + /* LZX: frame compressed */
> + if (!sbi->compress.lzx) {
> + /* Lazy initialize lzx decompress context */
> + spin_unlock(&sbi->compress.lock);
> + ctx = lzx_allocate_decompressor(0x8000);
> + if (!ctx)
> + return -ENOMEM;
> + if (IS_ERR(ctx)) {
> + /* should never failed */
> + err = PTR_ERR(ctx);
> + goto out;
> + }
> +
> + spin_lock(&sbi->compress.lock);
> + if (!sbi->compress.lzx) {
> + sbi->compress.lzx = ctx;
> + ctx = NULL;
> + }
> + }
> +
> + if (lzx_decompress(sbi->compress.lzx, cmpr, cmpr_size, unc,
> + unc_size)) {
> + err = -EINVAL;
> + }
> + } else {
> + /* XPRESS: frame compressed */
> + if (!sbi->compress.xpress) {
> + /* Lazy initialize xpress decompress context */
> + spin_unlock(&sbi->compress.lock);
> + ctx = xpress_allocate_decompressor();
> + if (!ctx)
> + return -ENOMEM;
> +
> + spin_lock(&sbi->compress.lock);
> + if (!sbi->compress.xpress) {
> + sbi->compress.xpress = ctx;
> + ctx = NULL;
> + }
> + }
> +
> + if (xpress_decompress(sbi->compress.xpress, cmpr, cmpr_size,
> + unc, unc_size)) {
> + err = -EINVAL;
> + }
> + }
> + spin_unlock(&sbi->compress.lock);
> +out:
> + ntfs_free(ctx);
> + return err;
> +}
Decompression is a somewhat heavyweight operation. Not the type of thing that
should be done while holding a spin lock.
- Eric
