Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 736 insertions, 0 deletions

diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c
new file mode 100644
index 000000000..86919293f
--- /dev/null
+++ b/fs/btrfs/zstd.c
@@ -0,0 +1,736 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2016-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ */
+
+#include <linux/bio.h>
+#include <linux/bitmap.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/sched/mm.h>
+#include <linux/pagemap.h>
+#include <linux/refcount.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/zstd.h>
+#include "misc.h"
+#include "fs.h"
+#include "btrfs_inode.h"
+#include "compression.h"
+#include "super.h"
+
+#define ZSTD_BTRFS_MAX_WINDOWLOG 17
+#define ZSTD_BTRFS_MAX_INPUT (1U << ZSTD_BTRFS_MAX_WINDOWLOG)
+#define ZSTD_BTRFS_DEFAULT_LEVEL 3
+#define ZSTD_BTRFS_MIN_LEVEL -15
+#define ZSTD_BTRFS_MAX_LEVEL 15
+/* 307s to avoid pathologically clashing with transaction commit */
+#define ZSTD_BTRFS_RECLAIM_JIFFIES (307 * HZ)
+
+static zstd_parameters zstd_get_btrfs_parameters(int level,
+						 size_t src_len)
+{
+	zstd_parameters params = zstd_get_params(level, src_len);
+
+	if (params.cParams.windowLog > ZSTD_BTRFS_MAX_WINDOWLOG)
+		params.cParams.windowLog = ZSTD_BTRFS_MAX_WINDOWLOG;
+	WARN_ON(src_len > ZSTD_BTRFS_MAX_INPUT);
+	return params;
+}
+
+struct workspace {
+	void *mem;
+	size_t size;
+	char *buf;
+	int level;
+	int req_level;
+	unsigned long last_used; /* jiffies */
+	struct list_head list;
+	struct list_head lru_list;
+	zstd_in_buffer in_buf;
+	zstd_out_buffer out_buf;
+	zstd_parameters params;
+};
+
+/*
+ * Zstd Workspace Management
+ *
+ * Zstd workspaces have different memory requirements depending on the level.
+ * The zstd workspaces are managed by having individual lists for each level
+ * and a global lru.  Forward progress is maintained by protecting a max level
+ * workspace.
+ *
+ * Getting a workspace is done by using the bitmap to identify the levels that
+ * have available workspaces and scans up.  This lets us recycle higher level
+ * workspaces because of the monotonic memory guarantee.  A workspace's
+ * last_used is only updated if it is being used by the corresponding memory
+ * level.  Putting a workspace involves adding it back to the appropriate places
+ * and adding it back to the lru if necessary.
+ *
+ * A timer is used to reclaim workspaces if they have not been used for
+ * ZSTD_BTRFS_RECLAIM_JIFFIES.  This helps keep only active workspaces around.
+ * The upper bound is provided by the workqueue limit which is 2 (percpu limit).
+ */
+
+struct zstd_workspace_manager {
+	spinlock_t lock;
+	struct list_head lru_list;
+	struct list_head idle_ws[ZSTD_BTRFS_MAX_LEVEL];
+	unsigned long active_map;
+	wait_queue_head_t wait;
+	struct timer_list timer;
+};
+
+static size_t zstd_ws_mem_sizes[ZSTD_BTRFS_MAX_LEVEL];
+
+static inline struct workspace *list_to_workspace(struct list_head *list)
+{
+	return container_of(list, struct workspace, list);
+}
+
+static inline int clip_level(int level)
+{
+	return max(0, level - 1);
+}
+
+/*
+ * Timer callback to free unused workspaces.
+ *
+ * @t: timer
+ *
+ * This scans the lru_list and attempts to reclaim any workspace that hasn't
+ * been used for ZSTD_BTRFS_RECLAIM_JIFFIES.
+ *
+ * The context is softirq and does not need the _bh locking primitives.
+ */
+static void zstd_reclaim_timer_fn(struct timer_list *timer)
+{
+	struct zstd_workspace_manager *zwsm =
+		container_of(timer, struct zstd_workspace_manager, timer);
+	unsigned long reclaim_threshold = jiffies - ZSTD_BTRFS_RECLAIM_JIFFIES;
+	struct list_head *pos, *next;
+
+	spin_lock(&zwsm->lock);
+
+	if (list_empty(&zwsm->lru_list)) {
+		spin_unlock(&zwsm->lock);
+		return;
+	}
+
+	list_for_each_prev_safe(pos, next, &zwsm->lru_list) {
+		struct workspace *victim = container_of(pos, struct workspace,
+							lru_list);
+		int level;
+
+		if (time_after(victim->last_used, reclaim_threshold))
+			break;
+
+		/* workspace is in use */
+		if (victim->req_level)
+			continue;
+
+		level = victim->level;
+		list_del(&victim->lru_list);
+		list_del(&victim->list);
+		zstd_free_workspace(&victim->list);
+
+		if (list_empty(&zwsm->idle_ws[level]))
+			clear_bit(level, &zwsm->active_map);
+
+	}
+
+	if (!list_empty(&zwsm->lru_list))
+		mod_timer(&zwsm->timer, jiffies + ZSTD_BTRFS_RECLAIM_JIFFIES);
+
+	spin_unlock(&zwsm->lock);
+}
+
+/*
+ * Calculate monotonic memory bounds.
+ *
+ * It is possible based on the level configurations that a higher level
+ * workspace uses less memory than a lower level workspace.  In order to reuse
+ * workspaces, this must be made a monotonic relationship.  This precomputes
+ * the required memory for each level and enforces the monotonicity between
+ * level and memory required.
+ */
+static void zstd_calc_ws_mem_sizes(void)
+{
+	size_t max_size = 0;
+	int level;
+
+	for (level = ZSTD_BTRFS_MIN_LEVEL; level <= ZSTD_BTRFS_MAX_LEVEL; level++) {
+		if (level == 0)
+			continue;
+		zstd_parameters params =
+			zstd_get_btrfs_parameters(level, ZSTD_BTRFS_MAX_INPUT);
+		size_t level_size =
+			max_t(size_t,
+			      zstd_cstream_workspace_bound(&params.cParams),
+			      zstd_dstream_workspace_bound(ZSTD_BTRFS_MAX_INPUT));
+
+		max_size = max_t(size_t, max_size, level_size);
+		/* Use level 1 workspace size for all the fast mode negative levels. */
+		zstd_ws_mem_sizes[clip_level(level)] = max_size;
+	}
+}
+
+int zstd_alloc_workspace_manager(struct btrfs_fs_info *fs_info)
+{
+	struct zstd_workspace_manager *zwsm;
+	struct list_head *ws;
+
+	ASSERT(fs_info->compr_wsm[BTRFS_COMPRESS_ZSTD] == NULL);
+	zwsm = kzalloc_obj(*zwsm);
+	if (!zwsm)
+		return -ENOMEM;
+	zstd_calc_ws_mem_sizes();
+	spin_lock_init(&zwsm->lock);
+	init_waitqueue_head(&zwsm->wait);
+	timer_setup(&zwsm->timer, zstd_reclaim_timer_fn, 0);
+
+	INIT_LIST_HEAD(&zwsm->lru_list);
+	for (int i = 0; i < ZSTD_BTRFS_MAX_LEVEL; i++)
+		INIT_LIST_HEAD(&zwsm->idle_ws[i]);
+	fs_info->compr_wsm[BTRFS_COMPRESS_ZSTD] = zwsm;
+
+	ws = zstd_alloc_workspace(fs_info, ZSTD_BTRFS_MAX_LEVEL);
+	if (IS_ERR(ws)) {
+		btrfs_warn(NULL, "cannot preallocate zstd compression workspace");
+	} else {
+		set_bit(ZSTD_BTRFS_MAX_LEVEL - 1, &zwsm->active_map);
+		list_add(ws, &zwsm->idle_ws[ZSTD_BTRFS_MAX_LEVEL - 1]);
+	}
+	return 0;
+}
+
+void zstd_free_workspace_manager(struct btrfs_fs_info *fs_info)
+{
+	struct zstd_workspace_manager *zwsm = fs_info->compr_wsm[BTRFS_COMPRESS_ZSTD];
+	struct workspace *workspace;
+
+	if (!zwsm)
+		return;
+	fs_info->compr_wsm[BTRFS_COMPRESS_ZSTD] = NULL;
+	spin_lock_bh(&zwsm->lock);
+	for (int i = 0; i < ZSTD_BTRFS_MAX_LEVEL; i++) {
+		while (!list_empty(&zwsm->idle_ws[i])) {
+			workspace = container_of(zwsm->idle_ws[i].next,
+						 struct workspace, list);
+			list_del(&workspace->list);
+			list_del(&workspace->lru_list);
+			zstd_free_workspace(&workspace->list);
+		}
+	}
+	spin_unlock_bh(&zwsm->lock);
+	timer_delete_sync(&zwsm->timer);
+	kfree(zwsm);
+}
+
+/*
+ * Find workspace for given level.
+ *
+ * @level: compression level
+ *
+ * This iterates over the set bits in the active_map beginning at the requested
+ * compression level.  This lets us utilize already allocated workspaces before
+ * allocating a new one.  If the workspace is of a larger size, it is used, but
+ * the place in the lru_list and last_used times are not updated.  This is to
+ * offer the opportunity to reclaim the workspace in favor of allocating an
+ * appropriately sized one in the future.
+ */
+static struct list_head *zstd_find_workspace(struct btrfs_fs_info *fs_info, int level)
+{
+	struct zstd_workspace_manager *zwsm = fs_info->compr_wsm[BTRFS_COMPRESS_ZSTD];
+	struct list_head *ws;
+	struct workspace *workspace;
+	int i = clip_level(level);
+
+	ASSERT(zwsm);
+	spin_lock_bh(&zwsm->lock);
+	for_each_set_bit_from(i, &zwsm->active_map, ZSTD_BTRFS_MAX_LEVEL) {
+		if (!list_empty(&zwsm->idle_ws[i])) {
+			ws = zwsm->idle_ws[i].next;
+			workspace = list_to_workspace(ws);
+			list_del_init(ws);
+			/* keep its place if it's a lower level using this */
+			workspace->req_level = level;
+			if (clip_level(level) == workspace->level)
+				list_del(&workspace->lru_list);
+			if (list_empty(&zwsm->idle_ws[i]))
+				clear_bit(i, &zwsm->active_map);
+			spin_unlock_bh(&zwsm->lock);
+			return ws;
+		}
+	}
+	spin_unlock_bh(&zwsm->lock);
+
+	return NULL;
+}
+
+/*
+ * Zstd get_workspace for level.
+ *
+ * @level: compression level
+ *
+ * If @level is 0, then any compression level can be used.  Therefore, we begin
+ * scanning from 1.  We first scan through possible workspaces and then after
+ * attempt to allocate a new workspace.  If we fail to allocate one due to
+ * memory pressure, go to sleep waiting for the max level workspace to free up.
+ */
+struct list_head *zstd_get_workspace(struct btrfs_fs_info *fs_info, int level)
+{
+	struct zstd_workspace_manager *zwsm = fs_info->compr_wsm[BTRFS_COMPRESS_ZSTD];
+	struct list_head *ws;
+	unsigned int nofs_flag;
+
+	ASSERT(zwsm);
+
+	/* level == 0 means we can use any workspace */
+	if (!level)
+		level = 1;
+
+again:
+	ws = zstd_find_workspace(fs_info, level);
+	if (ws)
+		return ws;
+
+	nofs_flag = memalloc_nofs_save();
+	ws = zstd_alloc_workspace(fs_info, level);
+	memalloc_nofs_restore(nofs_flag);
+
+	if (IS_ERR(ws)) {
+		DEFINE_WAIT(wait);
+
+		prepare_to_wait(&zwsm->wait, &wait, TASK_UNINTERRUPTIBLE);
+		schedule();
+		finish_wait(&zwsm->wait, &wait);
+
+		goto again;
+	}
+
+	return ws;
+}
+
+/*
+ * Zstd put_workspace.
+ *
+ * @ws: list_head for the workspace
+ *
+ * When putting back a workspace, we only need to update the LRU if we are of
+ * the requested compression level.  Here is where we continue to protect the
+ * max level workspace or update last_used accordingly.  If the reclaim timer
+ * isn't set, it is also set here.  Only the max level workspace tries and wakes
+ * up waiting workspaces.
+ */
+void zstd_put_workspace(struct btrfs_fs_info *fs_info, struct list_head *ws)
+{
+	struct zstd_workspace_manager *zwsm = fs_info->compr_wsm[BTRFS_COMPRESS_ZSTD];
+	struct workspace *workspace = list_to_workspace(ws);
+
+	ASSERT(zwsm);
+	spin_lock_bh(&zwsm->lock);
+
+	/* A node is only taken off the lru if we are the corresponding level */
+	if (clip_level(workspace->req_level) == workspace->level) {
+		/* Hide a max level workspace from reclaim */
+		if (list_empty(&zwsm->idle_ws[ZSTD_BTRFS_MAX_LEVEL - 1])) {
+			INIT_LIST_HEAD(&workspace->lru_list);
+		} else {
+			workspace->last_used = jiffies;
+			list_add(&workspace->lru_list, &zwsm->lru_list);
+			if (!timer_pending(&zwsm->timer))
+				mod_timer(&zwsm->timer,
+					  jiffies + ZSTD_BTRFS_RECLAIM_JIFFIES);
+		}
+	}
+
+	set_bit(workspace->level, &zwsm->active_map);
+	list_add(&workspace->list, &zwsm->idle_ws[workspace->level]);
+	workspace->req_level = 0;
+
+	spin_unlock_bh(&zwsm->lock);
+
+	if (workspace->level == clip_level(ZSTD_BTRFS_MAX_LEVEL))
+		cond_wake_up(&zwsm->wait);
+}
+
+void zstd_free_workspace(struct list_head *ws)
+{
+	struct workspace *workspace = list_entry(ws, struct workspace, list);
+
+	kvfree(workspace->mem);
+	kfree(workspace->buf);
+	kfree(workspace);
+}
+
+struct list_head *zstd_alloc_workspace(struct btrfs_fs_info *fs_info, int level)
+{
+	struct workspace *workspace;
+
+	workspace = kzalloc_obj(*workspace);
+	if (!workspace)
+		return ERR_PTR(-ENOMEM);
+
+	/* Use level 1 workspace size for all the fast mode negative levels. */
+	workspace->size = zstd_ws_mem_sizes[clip_level(level)];
+	workspace->level = clip_level(level);
+	workspace->req_level = level;
+	workspace->last_used = jiffies;
+	workspace->mem = kvmalloc(workspace->size, GFP_KERNEL | __GFP_NOWARN);
+	workspace->buf = kmalloc(fs_info->sectorsize, GFP_KERNEL);
+	if (!workspace->mem || !workspace->buf)
+		goto fail;
+
+	INIT_LIST_HEAD(&workspace->list);
+	INIT_LIST_HEAD(&workspace->lru_list);
+
+	return &workspace->list;
+fail:
+	zstd_free_workspace(&workspace->list);
+	return ERR_PTR(-ENOMEM);
+}
+
+int zstd_compress_bio(struct list_head *ws, struct compressed_bio *cb)
+{
+	struct btrfs_inode *inode = cb->bbio.inode;
+	struct btrfs_fs_info *fs_info = inode->root->fs_info;
+	struct workspace *workspace = list_entry(ws, struct workspace, list);
+	struct address_space *mapping = inode->vfs_inode.i_mapping;
+	struct bio *bio = &cb->bbio.bio;
+	zstd_cstream *stream;
+	int ret = 0;
+	/* The current folio to read. */
+	struct folio *in_folio = NULL;
+	/* The current folio to write to. */
+	struct folio *out_folio = NULL;
+	unsigned long tot_in = 0;
+	unsigned long tot_out = 0;
+	const u64 start = cb->start;
+	const u32 len = cb->len;
+	const u64 end = start + len;
+	const u32 min_folio_size = btrfs_min_folio_size(fs_info);
+
+	workspace->params = zstd_get_btrfs_parameters(workspace->req_level, len);
+
+	/* Initialize the stream. */
+	stream = zstd_init_cstream(&workspace->params, len, workspace->mem, workspace->size);
+	if (unlikely(!stream)) {
+		btrfs_err(fs_info,
+	"zstd compression init level %d failed, root %llu inode %llu offset %llu",
+			  workspace->req_level, btrfs_root_id(inode->root),
+			  btrfs_ino(inode), start);
+		ret = -EIO;
+		goto out;
+	}
+
+	/* Map in the first page of input data. */
+	ret = btrfs_compress_filemap_get_folio(mapping, start, &in_folio);
+	if (ret < 0)
+		goto out;
+	workspace->in_buf.src = kmap_local_folio(in_folio, offset_in_folio(in_folio, start));
+	workspace->in_buf.pos = 0;
+	workspace->in_buf.size = btrfs_calc_input_length(in_folio, end, start);
+
+	/* Allocate and map in the output buffer. */
+	out_folio = btrfs_alloc_compr_folio(fs_info, GFP_NOFS);
+	if (out_folio == NULL) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	workspace->out_buf.dst = folio_address(out_folio);
+	workspace->out_buf.pos = 0;
+	workspace->out_buf.size = min_folio_size;
+
+	while (1) {
+		size_t ret2;
+
+		ret2 = zstd_compress_stream(stream, &workspace->out_buf, &workspace->in_buf);
+		if (unlikely(zstd_is_error(ret2))) {
+			btrfs_warn(fs_info,
+"zstd compression level %d failed, error %d root %llu inode %llu offset %llu",
+				   workspace->req_level, zstd_get_error_code(ret2),
+				   btrfs_root_id(inode->root), btrfs_ino(inode),
+				   start + tot_in);
+			ret = -EIO;
+			goto out;
+		}
+
+		/* Check to see if we are making it bigger. */
+		if (tot_in + workspace->in_buf.pos > fs_info->sectorsize * 2 &&
+		    tot_in + workspace->in_buf.pos < tot_out + workspace->out_buf.pos) {
+			ret = -E2BIG;
+			goto out;
+		}
+
+		/* Check if we need more output space. */
+		if (workspace->out_buf.pos >= workspace->out_buf.size) {
+			tot_out += min_folio_size;
+			if (tot_out >= len) {
+				ret = -E2BIG;
+				goto out;
+			}
+			/* Queue the current foliot into the bio. */
+			if (!bio_add_folio(bio, out_folio, folio_size(out_folio), 0)) {
+				ret = -E2BIG;
+				goto out;
+			}
+
+			out_folio = btrfs_alloc_compr_folio(fs_info, GFP_NOFS);
+			if (out_folio == NULL) {
+				ret = -ENOMEM;
+				goto out;
+			}
+			workspace->out_buf.dst = folio_address(out_folio);
+			workspace->out_buf.pos = 0;
+			workspace->out_buf.size = min_folio_size;
+		}
+
+		/* We've reached the end of the input. */
+		if (tot_in + workspace->in_buf.pos >= len) {
+			tot_in += workspace->in_buf.pos;
+			break;
+		}
+
+		/* Check if we need more input. */
+		if (workspace->in_buf.pos >= workspace->in_buf.size) {
+			u64 cur;
+
+			tot_in += workspace->in_buf.size;
+			cur = start + tot_in;
+
+			kunmap_local(workspace->in_buf.src);
+			workspace->in_buf.src = NULL;
+			folio_put(in_folio);
+
+			ret = btrfs_compress_filemap_get_folio(mapping, cur, &in_folio);
+			if (ret < 0)
+				goto out;
+			workspace->in_buf.src = kmap_local_folio(in_folio,
+							 offset_in_folio(in_folio, cur));
+			workspace->in_buf.pos = 0;
+			workspace->in_buf.size = btrfs_calc_input_length(in_folio, end, cur);
+		}
+	}
+
+	while (1) {
+		size_t ret2;
+
+		ret2 = zstd_end_stream(stream, &workspace->out_buf);
+		if (unlikely(zstd_is_error(ret2))) {
+			btrfs_err(fs_info,
+"zstd compression end level %d failed, error %d root %llu inode %llu offset %llu",
+				  workspace->req_level, zstd_get_error_code(ret2),
+				  btrfs_root_id(inode->root), btrfs_ino(inode),
+				  start + tot_in);
+			ret = -EIO;
+			goto out;
+		}
+		/* Queue the remaining part of the output folio into bio. */
+		if (ret2 == 0) {
+			tot_out += workspace->out_buf.pos;
+			if (tot_out >= len) {
+				ret = -E2BIG;
+				goto out;
+			}
+			if (!bio_add_folio(bio, out_folio, workspace->out_buf.pos, 0)) {
+				ret = -E2BIG;
+				goto out;
+			}
+			out_folio = NULL;
+			break;
+		}
+		tot_out += min_folio_size;
+		if (tot_out >= len) {
+			ret = -E2BIG;
+			goto out;
+		}
+		if (!bio_add_folio(bio, out_folio, folio_size(out_folio), 0)) {
+			ret = -E2BIG;
+			goto out;
+		}
+		out_folio = btrfs_alloc_compr_folio(fs_info, GFP_NOFS);
+		if (out_folio == NULL) {
+			ret = -ENOMEM;
+			goto out;
+		}
+		workspace->out_buf.dst = folio_address(out_folio);
+		workspace->out_buf.pos = 0;
+		workspace->out_buf.size = min_folio_size;
+	}
+
+	if (tot_out >= tot_in) {
+		ret = -E2BIG;
+		goto out;
+	}
+
+	ret = 0;
+	ASSERT(tot_out == bio->bi_iter.bi_size);
+out:
+	if (out_folio)
+		btrfs_free_compr_folio(out_folio);
+	if (workspace->in_buf.src) {
+		kunmap_local(workspace->in_buf.src);
+		folio_put(in_folio);
+	}
+	return ret;
+}
+
+int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
+{
+	struct btrfs_fs_info *fs_info = cb_to_fs_info(cb);
+	struct workspace *workspace = list_entry(ws, struct workspace, list);
+	struct folio_iter fi;
+	size_t srclen = bio_get_size(&cb->bbio.bio);
+	zstd_dstream *stream;
+	int ret = 0;
+	const unsigned int min_folio_size = btrfs_min_folio_size(fs_info);
+	unsigned long folio_in_index = 0;
+	unsigned long total_folios_in = DIV_ROUND_UP(srclen, min_folio_size);
+	unsigned long buf_start;
+	unsigned long total_out = 0;
+
+	bio_first_folio(&fi, &cb->bbio.bio, 0);
+	if (unlikely(!fi.folio))
+		return -EINVAL;
+	ASSERT(folio_size(fi.folio) == min_folio_size);
+
+	stream = zstd_init_dstream(
+			ZSTD_BTRFS_MAX_INPUT, workspace->mem, workspace->size);
+	if (unlikely(!stream)) {
+		struct btrfs_inode *inode = cb->bbio.inode;
+
+		btrfs_err(inode->root->fs_info,
+		"zstd decompression init failed, root %llu inode %llu offset %llu",
+			  btrfs_root_id(inode->root), btrfs_ino(inode), cb->start);
+		ret = -EIO;
+		goto done;
+	}
+
+	workspace->in_buf.src = kmap_local_folio(fi.folio, 0);
+	workspace->in_buf.pos = 0;
+	workspace->in_buf.size = min_t(size_t, srclen, min_folio_size);
+
+	workspace->out_buf.dst = workspace->buf;
+	workspace->out_buf.pos = 0;
+	workspace->out_buf.size = fs_info->sectorsize;
+
+	while (1) {
+		size_t ret2;
+
+		ret2 = zstd_decompress_stream(stream, &workspace->out_buf,
+				&workspace->in_buf);
+		if (unlikely(zstd_is_error(ret2))) {
+			struct btrfs_inode *inode = cb->bbio.inode;
+
+			btrfs_err(inode->root->fs_info,
+		"zstd decompression failed, error %d root %llu inode %llu offset %llu",
+				  zstd_get_error_code(ret2), btrfs_root_id(inode->root),
+				  btrfs_ino(inode), cb->start);
+			ret = -EIO;
+			goto done;
+		}
+		buf_start = total_out;
+		total_out += workspace->out_buf.pos;
+		workspace->out_buf.pos = 0;
+
+		ret = btrfs_decompress_buf2page(workspace->out_buf.dst,
+				total_out - buf_start, cb, buf_start);
+		if (ret == 0)
+			break;
+
+		if (workspace->in_buf.pos >= srclen)
+			break;
+
+		/* Check if we've hit the end of a frame */
+		if (ret2 == 0)
+			break;
+
+		if (workspace->in_buf.pos == workspace->in_buf.size) {
+			kunmap_local(workspace->in_buf.src);
+			folio_in_index++;
+			if (unlikely(folio_in_index >= total_folios_in)) {
+				workspace->in_buf.src = NULL;
+				ret = -EIO;
+				goto done;
+			}
+			srclen -= min_folio_size;
+			bio_next_folio(&fi, &cb->bbio.bio);
+			ASSERT(fi.folio);
+			workspace->in_buf.src = kmap_local_folio(fi.folio, 0);
+			workspace->in_buf.pos = 0;
+			workspace->in_buf.size = min_t(size_t, srclen, min_folio_size);
+		}
+	}
+	ret = 0;
+done:
+	if (workspace->in_buf.src)
+		kunmap_local(workspace->in_buf.src);
+	return ret;
+}
+
+int zstd_decompress(struct list_head *ws, const u8 *data_in,
+		struct folio *dest_folio, unsigned long dest_pgoff, size_t srclen,
+		size_t destlen)
+{
+	struct workspace *workspace = list_entry(ws, struct workspace, list);
+	struct btrfs_fs_info *fs_info = btrfs_sb(folio_inode(dest_folio)->i_sb);
+	zstd_dstream *stream;
+	int ret = 0;
+	unsigned long to_copy = 0;
+
+	stream = zstd_init_dstream(
+			ZSTD_BTRFS_MAX_INPUT, workspace->mem, workspace->size);
+	if (unlikely(!stream)) {
+		struct btrfs_inode *inode = folio_to_inode(dest_folio);
+
+		btrfs_err(inode->root->fs_info,
+		"zstd decompression init failed, root %llu inode %llu offset %llu",
+			  btrfs_root_id(inode->root), btrfs_ino(inode),
+			  folio_pos(dest_folio));
+		ret = -EIO;
+		goto finish;
+	}
+
+	workspace->in_buf.src = data_in;
+	workspace->in_buf.pos = 0;
+	workspace->in_buf.size = srclen;
+
+	workspace->out_buf.dst = workspace->buf;
+	workspace->out_buf.pos = 0;
+	workspace->out_buf.size = fs_info->sectorsize;
+
+	/*
+	 * Since both input and output buffers should not exceed one sector,
+	 * one call should end the decompression.
+	 */
+	ret = zstd_decompress_stream(stream, &workspace->out_buf, &workspace->in_buf);
+	if (unlikely(zstd_is_error(ret))) {
+		struct btrfs_inode *inode = folio_to_inode(dest_folio);
+
+		btrfs_err(inode->root->fs_info,
+		"zstd decompression failed, error %d root %llu inode %llu offset %llu",
+			  zstd_get_error_code(ret), btrfs_root_id(inode->root),
+			  btrfs_ino(inode), folio_pos(dest_folio));
+		goto finish;
+	}
+	to_copy = workspace->out_buf.pos;
+	memcpy_to_folio(dest_folio, dest_pgoff, workspace->out_buf.dst, to_copy);
+finish:
+	/* Error or early end. */
+	if (unlikely(to_copy < destlen)) {
+		ret = -EIO;
+		folio_zero_range(dest_folio, dest_pgoff + to_copy, destlen - to_copy);
+	}
+	return ret;
+}
+
+const struct btrfs_compress_levels btrfs_zstd_compress = {
+	.min_level	= ZSTD_BTRFS_MIN_LEVEL,
+	.max_level	= ZSTD_BTRFS_MAX_LEVEL,
+	.default_level	= ZSTD_BTRFS_DEFAULT_LEVEL,
+};