ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 372 insertions, 0 deletions

diff --git a/fs/smb/client/compress.c b/fs/smb/client/compress.c
new file mode 100644
index 000000000..8f0860970
--- /dev/null
+++ b/fs/smb/client/compress.c
@@ -0,0 +1,372 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2024, SUSE LLC
+ *
+ * Authors: Enzo Matsumiya <ematsumiya@suse.de>
+ *
+ * This file implements I/O compression support for SMB2 messages (SMB 3.1.1 only).
+ * See compress/ for implementation details of each algorithm.
+ *
+ * References:
+ * MS-SMB2 "3.1.4.4 Compressing the Message"
+ * MS-SMB2 "3.1.5.3 Decompressing the Chained Message"
+ * MS-XCA - for details of the supported algorithms
+ */
+#include <linux/slab.h>
+#include <linux/kernel.h>
+#include <linux/uio.h>
+#include <linux/sort.h>
+
+#include "cifsglob.h"
+#include "../common/smb2pdu.h"
+#include "cifsproto.h"
+#include "smb2proto.h"
+
+#include "../common/compress/lz77.h"
+#include "compress.h"
+
+/*
+ * The heuristic_*() functions below try to determine data compressibility.
+ *
+ * Derived from fs/btrfs/compression.c, changing coding style, some parameters, and removing
+ * unused parts.
+ *
+ * Read that file for better and more detailed explanation of the calculations.
+ *
+ * The algorithms are ran in a collected sample of the input (uncompressed) data.
+ * The sample is formed of 2K reads in PAGE_SIZE intervals, with a maximum size of 4M.
+ *
+ * Parsing the sample goes from "low-hanging fruits" (fastest algorithms, likely compressible)
+ * to "need more analysis" (likely uncompressible).
+ */
+
+struct bucket {
+	unsigned int count;
+};
+
+static inline size_t pow4(size_t n)
+{
+	return n * n * n * n;
+}
+
+/*
+ * has_low_entropy() - Compute Shannon entropy of the sampled data.
+ * @bkt:	Bytes counts of the sample.
+ * @slen:	Size of the sample.
+ *
+ * Return: true if the level (percentage of number of bits that would be required to
+ *	   compress the data) is below the minimum threshold.
+ *
+ * Note:
+ * There _is_ an entropy level here that's > 65 (minimum threshold) that would indicate a
+ * possibility of compression, but compressing, or even further analysing, it would waste so much
+ * resources that it's simply not worth it.
+ *
+ * Also Shannon entropy is the last computed heuristic; if we got this far and ended up
+ * with uncertainty, just stay on the safe side and call it uncompressible.
+ */
+static bool has_low_entropy(struct bucket *bkt, size_t slen)
+{
+	const size_t threshold = 65, max_entropy = 8 * ilog2(16);
+	size_t i, p, p2, len, sum = 0;
+
+	len = ilog2(pow4(slen));
+
+	for (i = 0; i < 256 && bkt[i].count > 0; i++) {
+		p = bkt[i].count;
+		p2 = ilog2(pow4(p));
+		sum += p * (len - p2);
+	}
+
+	sum /= slen;
+
+	return ((sum * 100 / max_entropy) <= threshold);
+}
+
+#define BYTE_DIST_BAD		0
+#define BYTE_DIST_GOOD		1
+#define BYTE_DIST_MAYBE		2
+/*
+ * calc_byte_distribution() - Compute byte distribution on the sampled data.
+ * @bkt:	Byte counts of the sample.
+ * @slen:	Size of the sample.
+ *
+ * Return:
+ * BYTE_DIST_BAD:	A "hard no" for compression -- a computed uniform distribution of
+ *			the bytes (e.g. random or encrypted data).
+ * BYTE_DIST_GOOD:	High probability (normal (Gaussian) distribution) of the data being
+ *			compressible.
+ * BYTE_DIST_MAYBE:	When computed byte distribution resulted in "low > n < high"
+ *			grounds.  has_low_entropy() should be used for a final decision.
+ */
+static int calc_byte_distribution(struct bucket *bkt, size_t slen)
+{
+	const size_t low = 64, high = 200, threshold = slen * 90 / 100;
+	size_t sum = 0;
+	int i;
+
+	for (i = 0; i < low; i++)
+		sum += bkt[i].count;
+
+	if (sum > threshold)
+		return BYTE_DIST_BAD;
+
+	for (; i < high && bkt[i].count > 0; i++) {
+		sum += bkt[i].count;
+		if (sum > threshold)
+			break;
+	}
+
+	if (i <= low)
+		return BYTE_DIST_GOOD;
+
+	if (i >= high)
+		return BYTE_DIST_BAD;
+
+	return BYTE_DIST_MAYBE;
+}
+
+static bool is_mostly_ascii(const struct bucket *bkt)
+{
+	size_t count = 0;
+	int i;
+
+	for (i = 0; i < 256; i++)
+		if (bkt[i].count > 0)
+			/* Too many non-ASCII (0-63) bytes. */
+			if (++count > 64)
+				return false;
+
+	return true;
+}
+
+static bool has_repeated_data(const u8 *sample, size_t len)
+{
+	size_t s = len / 2;
+
+	return (!memcmp(&sample[0], &sample[s], s));
+}
+
+static int cmp_bkt(const void *_a, const void *_b)
+{
+	const struct bucket *a = _a, *b = _b;
+
+	/* Reverse sort. */
+	if (a->count > b->count)
+		return -1;
+
+	return 1;
+}
+
+/*
+ * Collect some 2K samples with 2K gaps between.
+ */
+static int collect_sample(const struct iov_iter *source, ssize_t max, u8 *sample)
+{
+	struct iov_iter iter = *source;
+	size_t s = 0;
+
+	while (iov_iter_count(&iter) >= SZ_2K) {
+		size_t part = umin(umin(iov_iter_count(&iter), SZ_2K), max);
+		size_t n;
+
+		n = copy_from_iter(sample + s, part, &iter);
+		if (n != part)
+			return -EFAULT;
+
+		s += n;
+		max -= n;
+
+		if (iov_iter_count(&iter) < PAGE_SIZE - SZ_2K)
+			break;
+
+		iov_iter_advance(&iter, SZ_2K);
+	}
+
+	return s;
+}
+
+/*
+ * is_compressible() - Determines if a chunk of data is compressible.
+ * @data: Iterator containing uncompressed data.
+ *
+ * Return: true if @data is compressible, false otherwise.
+ *
+ * Tests shows that this function is quite reliable in predicting data compressibility,
+ * matching close to 1:1 with the behaviour of LZ77 compression success and failures.
+ */
+static bool is_compressible(const struct iov_iter *data)
+{
+	const size_t read_size = SZ_2K, bkt_size = 256, max = SZ_4M;
+	struct bucket *bkt = NULL;
+	size_t len;
+	u8 *sample;
+	bool ret = false;
+	int i;
+
+	/* Preventive double check -- already checked in should_compress(). */
+	len = iov_iter_count(data);
+	if (unlikely(len < read_size))
+		return ret;
+
+	if (len - read_size > max)
+		len = max;
+
+	sample = kvzalloc(len, GFP_KERNEL);
+	if (!sample) {
+		WARN_ON_ONCE(1);
+
+		return ret;
+	}
+
+	/* Sample 2K bytes per page of the uncompressed data. */
+	i = collect_sample(data, len, sample);
+	if (i <= 0) {
+		WARN_ON_ONCE(1);
+
+		goto out;
+	}
+
+	len = i;
+	ret = true;
+
+	if (has_repeated_data(sample, len))
+		goto out;
+
+	bkt = kzalloc_objs(*bkt, bkt_size);
+	if (!bkt) {
+		WARN_ON_ONCE(1);
+		ret = false;
+
+		goto out;
+	}
+
+	for (i = 0; i < len; i++)
+		bkt[sample[i]].count++;
+
+	if (is_mostly_ascii(bkt))
+		goto out;
+
+	/* Sort in descending order */
+	sort(bkt, bkt_size, sizeof(*bkt), cmp_bkt, NULL);
+
+	i = calc_byte_distribution(bkt, len);
+	if (i != BYTE_DIST_MAYBE) {
+		ret = !!i;
+
+		goto out;
+	}
+
+	ret = has_low_entropy(bkt, len);
+out:
+	kvfree(sample);
+	kfree(bkt);
+
+	return ret;
+}
+
+/*
+ * should_compress() - Determines if a request (write) or the response to a
+ *		       request (read) should be compressed.
+ * @tcon: tcon of the request is being sent to
+ * @rqst: request to evaluate
+ *
+ * Return: true iff:
+ * - compression was successfully negotiated with server
+ * - server has enabled compression for the share
+ * - it's a read or write request
+ * - (write only) request length is >= SMB_COMPRESS_MIN_LEN
+ * - (write only) is_compressible() returns 1
+ *
+ * Return false otherwise.
+ */
+bool should_compress(const struct cifs_tcon *tcon, const struct smb_rqst *rq)
+{
+	const struct smb2_hdr *shdr = rq->rq_iov->iov_base;
+
+	if (unlikely(!tcon || !tcon->ses || !tcon->ses->server))
+		return false;
+
+	if (!tcon->ses->server->compression.enabled)
+		return false;
+
+	if (!(tcon->share_flags & SMB2_SHAREFLAG_COMPRESS_DATA))
+		return false;
+
+	if (shdr->Command == SMB2_WRITE) {
+		const struct smb2_write_req *wreq = rq->rq_iov->iov_base;
+
+		if (le32_to_cpu(wreq->Length) < SMB_COMPRESS_MIN_LEN)
+			return false;
+
+		return is_compressible(&rq->rq_iter);
+	}
+
+	return (shdr->Command == SMB2_READ);
+}
+
+int smb_compress(struct TCP_Server_Info *server, struct smb_rqst *rq, compress_send_fn send_fn)
+{
+	struct iov_iter iter;
+	u32 slen, dlen;
+	void *src, *dst = NULL;
+	int ret;
+
+	if (!server || !rq || !rq->rq_iov || !rq->rq_iov->iov_base)
+		return -EINVAL;
+
+	if (rq->rq_iov->iov_len != sizeof(struct smb2_write_req))
+		return -EINVAL;
+
+	slen = iov_iter_count(&rq->rq_iter);
+	src = kvzalloc(slen, GFP_KERNEL);
+	if (!src) {
+		ret = -ENOMEM;
+		goto err_free;
+	}
+
+	/* Keep the original iter intact. */
+	iter = rq->rq_iter;
+
+	if (!copy_from_iter_full(src, slen, &iter)) {
+		ret = smb_EIO(smb_eio_trace_compress_copy);
+		goto err_free;
+	}
+
+	dlen = smb_lz77_compressed_alloc_size(slen);
+	dst = kvzalloc(dlen, GFP_KERNEL);
+	if (!dst) {
+		ret = -ENOMEM;
+		goto err_free;
+	}
+
+	ret = smb_lz77_compress(src, slen, dst, &dlen);
+	if (!ret) {
+		struct smb2_compression_hdr hdr = { 0 };
+		struct smb_rqst comp_rq = { .rq_nvec = 3, };
+		struct kvec iov[3];
+
+		hdr.ProtocolId = SMB2_COMPRESSION_TRANSFORM_ID;
+		hdr.OriginalCompressedSegmentSize = cpu_to_le32(slen);
+		hdr.CompressionAlgorithm = SMB3_COMPRESS_LZ77;
+		hdr.Flags = SMB2_COMPRESSION_FLAG_NONE;
+		hdr.Offset = cpu_to_le32(rq->rq_iov[0].iov_len);
+
+		iov[0].iov_base = &hdr;
+		iov[0].iov_len = sizeof(hdr);
+		iov[1] = rq->rq_iov[0];
+		iov[2].iov_base = dst;
+		iov[2].iov_len = dlen;
+
+		comp_rq.rq_iov = iov;
+
+		ret = send_fn(server, 1, &comp_rq);
+	} else if (ret == -EMSGSIZE || dlen >= slen) {
+		ret = send_fn(server, 1, rq);
+	}
+err_free:
+	kvfree(dst);
+	kvfree(src);
+
+	return ret;
+}