--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <linux/zstd.h>
+#include "compress.h"
+
+struct z_erofs_zstd {
+ struct z_erofs_zstd *next;
+ u8 bounce[PAGE_SIZE];
+ void *wksp;
+ unsigned int wkspsz;
+};
+
+static DEFINE_SPINLOCK(z_erofs_zstd_lock);
+static unsigned int z_erofs_zstd_max_dictsize;
+static unsigned int z_erofs_zstd_nstrms, z_erofs_zstd_avail_strms;
+static struct z_erofs_zstd *z_erofs_zstd_head;
+static DECLARE_WAIT_QUEUE_HEAD(z_erofs_zstd_wq);
+
+module_param_named(zstd_streams, z_erofs_zstd_nstrms, uint, 0444);
+
+static struct z_erofs_zstd *z_erofs_isolate_strms(bool all)
+{
+ struct z_erofs_zstd *strm;
+
+again:
+ spin_lock(&z_erofs_zstd_lock);
+ strm = z_erofs_zstd_head;
+ if (!strm) {
+ spin_unlock(&z_erofs_zstd_lock);
+ wait_event(z_erofs_zstd_wq, READ_ONCE(z_erofs_zstd_head));
+ goto again;
+ }
+ z_erofs_zstd_head = all ? NULL : strm->next;
+ spin_unlock(&z_erofs_zstd_lock);
+ return strm;
+}
+
+void z_erofs_zstd_exit(void)
+{
+ while (z_erofs_zstd_avail_strms) {
+ struct z_erofs_zstd *strm, *n;
+
+ for (strm = z_erofs_isolate_strms(true); strm; strm = n) {
+ n = strm->next;
+
+ kvfree(strm->wksp);
+ kfree(strm);
+ --z_erofs_zstd_avail_strms;
+ }
+ }
+}
+
+int __init z_erofs_zstd_init(void)
+{
+ /* by default, use # of possible CPUs instead */
+ if (!z_erofs_zstd_nstrms)
+ z_erofs_zstd_nstrms = num_possible_cpus();
+
+ for (; z_erofs_zstd_avail_strms < z_erofs_zstd_nstrms;
+ ++z_erofs_zstd_avail_strms) {
+ struct z_erofs_zstd *strm;
+
+ strm = kzalloc(sizeof(*strm), GFP_KERNEL);
+ if (!strm) {
+ z_erofs_zstd_exit();
+ return -ENOMEM;
+ }
+ spin_lock(&z_erofs_zstd_lock);
+ strm->next = z_erofs_zstd_head;
+ z_erofs_zstd_head = strm;
+ spin_unlock(&z_erofs_zstd_lock);
+ }
+ return 0;
+}
+
+int z_erofs_load_zstd_config(struct super_block *sb,
+ struct erofs_super_block *dsb, void *data, int size)
+{
+ static DEFINE_MUTEX(zstd_resize_mutex);
+ struct z_erofs_zstd_cfgs *zstd = data;
+ unsigned int dict_size, wkspsz;
+ struct z_erofs_zstd *strm, *head = NULL;
+ void *wksp;
+
+ if (!zstd || size < sizeof(struct z_erofs_zstd_cfgs) || zstd->format) {
+ erofs_err(sb, "unsupported zstd format, size=%u", size);
+ return -EINVAL;
+ }
+
+ if (zstd->windowlog > ilog2(Z_EROFS_ZSTD_MAX_DICT_SIZE) - 10) {
+ erofs_err(sb, "unsupported zstd window log %u", zstd->windowlog);
+ return -EINVAL;
+ }
+ dict_size = 1U << (zstd->windowlog + 10);
+
+ /* in case 2 z_erofs_load_zstd_config() race to avoid deadlock */
+ mutex_lock(&zstd_resize_mutex);
+ if (z_erofs_zstd_max_dictsize >= dict_size) {
+ mutex_unlock(&zstd_resize_mutex);
+ return 0;
+ }
+
+ /* 1. collect/isolate all streams for the following check */
+ while (z_erofs_zstd_avail_strms) {
+ struct z_erofs_zstd *n;
+
+ for (strm = z_erofs_isolate_strms(true); strm; strm = n) {
+ n = strm->next;
+ strm->next = head;
+ head = strm;
+ --z_erofs_zstd_avail_strms;
+ }
+ }
+
+ /* 2. walk each isolated stream and grow max dict_size if needed */
+ wkspsz = zstd_dstream_workspace_bound(dict_size);
+ for (strm = head; strm; strm = strm->next) {
+ wksp = kvmalloc(wkspsz, GFP_KERNEL);
+ if (!wksp)
+ break;
+ kvfree(strm->wksp);
+ strm->wksp = wksp;
+ strm->wkspsz = wkspsz;
+ }
+
+ /* 3. push back all to the global list and update max dict_size */
+ spin_lock(&z_erofs_zstd_lock);
+ DBG_BUGON(z_erofs_zstd_head);
+ z_erofs_zstd_head = head;
+ spin_unlock(&z_erofs_zstd_lock);
+ z_erofs_zstd_avail_strms = z_erofs_zstd_nstrms;
+ wake_up_all(&z_erofs_zstd_wq);
+ if (!strm)
+ z_erofs_zstd_max_dictsize = dict_size;
+ mutex_unlock(&zstd_resize_mutex);
+ return strm ? -ENOMEM : 0;
+}
+
+int z_erofs_zstd_decompress(struct z_erofs_decompress_req *rq,
+ struct page **pgpl)
+{
+ const unsigned int nrpages_out =
+ PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
+ const unsigned int nrpages_in =
+ PAGE_ALIGN(rq->inputsize) >> PAGE_SHIFT;
+ zstd_dstream *stream;
+ struct super_block *sb = rq->sb;
+ unsigned int insz, outsz, pofs;
+ struct z_erofs_zstd *strm;
+ zstd_in_buffer in_buf = { NULL, 0, 0 };
+ zstd_out_buffer out_buf = { NULL, 0, 0 };
+ u8 *kin, *kout = NULL;
+ bool bounced = false;
+ int no = -1, ni = 0, j = 0, zerr, err;
+
+ /* 1. get the exact compressed size */
+ kin = kmap_local_page(*rq->in);
+ err = z_erofs_fixup_insize(rq, kin + rq->pageofs_in,
+ min_t(unsigned int, rq->inputsize,
+ sb->s_blocksize - rq->pageofs_in));
+ if (err) {
+ kunmap_local(kin);
+ return err;
+ }
+
+ /* 2. get an available ZSTD context */
+ strm = z_erofs_isolate_strms(false);
+
+ /* 3. multi-call decompress */
+ insz = rq->inputsize;
+ outsz = rq->outputsize;
+ stream = zstd_init_dstream(z_erofs_zstd_max_dictsize, strm->wksp, strm->wkspsz);
+ if (!stream) {
+ err = -EIO;
+ goto failed_zinit;
+ }
+
+ pofs = rq->pageofs_out;
+ in_buf.size = min_t(u32, insz, PAGE_SIZE - rq->pageofs_in);
+ insz -= in_buf.size;
+ in_buf.src = kin + rq->pageofs_in;
+ do {
+ if (out_buf.size == out_buf.pos) {
+ if (++no >= nrpages_out || !outsz) {
+ erofs_err(sb, "insufficient space for decompressed data");
+ err = -EFSCORRUPTED;
+ break;
+ }
+
+ if (kout)
+ kunmap_local(kout);
+ out_buf.size = min_t(u32, outsz, PAGE_SIZE - pofs);
+ outsz -= out_buf.size;
+ if (!rq->out[no]) {
+ rq->out[no] = erofs_allocpage(pgpl, rq->gfp);
+ if (!rq->out[no]) {
+ kout = NULL;
+ err = -ENOMEM;
+ break;
+ }
+ set_page_private(rq->out[no],
+ Z_EROFS_SHORTLIVED_PAGE);
+ }
+ kout = kmap_local_page(rq->out[no]);
+ out_buf.dst = kout + pofs;
+ out_buf.pos = 0;
+ pofs = 0;
+ }
+
+ if (in_buf.size == in_buf.pos && insz) {
+ if (++ni >= nrpages_in) {
+ erofs_err(sb, "invalid compressed data");
+ err = -EFSCORRUPTED;
+ break;
+ }
+
+ if (kout) /* unlike kmap(), take care of the orders */
+ kunmap_local(kout);
+ kunmap_local(kin);
+ in_buf.size = min_t(u32, insz, PAGE_SIZE);
+ insz -= in_buf.size;
+ kin = kmap_local_page(rq->in[ni]);
+ in_buf.src = kin;
+ in_buf.pos = 0;
+ bounced = false;
+ if (kout) {
+ j = (u8 *)out_buf.dst - kout;
+ kout = kmap_local_page(rq->out[no]);
+ out_buf.dst = kout + j;
+ }
+ }
+
+ /*
+ * Handle overlapping: Use bounced buffer if the compressed
+ * data is under processing; Or use short-lived pages from the
+ * on-stack pagepool where pages share among the same request
+ * and not _all_ inplace I/O pages are needed to be doubled.
+ */
+ if (!bounced && rq->out[no] == rq->in[ni]) {
+ memcpy(strm->bounce, in_buf.src, in_buf.size);
+ in_buf.src = strm->bounce;
+ bounced = true;
+ }
+
+ for (j = ni + 1; j < nrpages_in; ++j) {
+ struct page *tmppage;
+
+ if (rq->out[no] != rq->in[j])
+ continue;
+ tmppage = erofs_allocpage(pgpl, rq->gfp);
+ if (!tmppage) {
+ err = -ENOMEM;
+ goto failed;
+ }
+ set_page_private(tmppage, Z_EROFS_SHORTLIVED_PAGE);
+ copy_highpage(tmppage, rq->in[j]);
+ rq->in[j] = tmppage;
+ }
+ zerr = zstd_decompress_stream(stream, &out_buf, &in_buf);
+ if (zstd_is_error(zerr) || (!zerr && outsz)) {
+ erofs_err(sb, "failed to decompress in[%u] out[%u]: %s",
+ rq->inputsize, rq->outputsize,
+ zerr ? zstd_get_error_name(zerr) : "unexpected end of stream");
+ err = -EFSCORRUPTED;
+ break;
+ }
+ } while (outsz || out_buf.pos < out_buf.size);
+failed:
+ if (kout)
+ kunmap_local(kout);
+failed_zinit:
+ kunmap_local(kin);
+ /* 4. push back ZSTD stream context to the global list */
+ spin_lock(&z_erofs_zstd_lock);
+ strm->next = z_erofs_zstd_head;
+ z_erofs_zstd_head = strm;
+ spin_unlock(&z_erofs_zstd_lock);
+ wake_up(&z_erofs_zstd_wq);
+ return err;
+}
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