zstd: import usptream v1.5.2

Updates the kernel's zstd library to v1.5.2, the latest zstd release.
The upstream tag it is updated to is `v1.5.2-kernel`, which contains
several cherry-picked commits on top of the v1.5.2 release which are
required for the kernel update. I will create this tag once the PR is
ready to merge, until then reference the temporary upstream branch
`v1.5.2-kernel-cherrypicks`.

I plan to submit this patch as part of the v6.2 merge window.

I've done basic build testing & testing on x86-64, i386, and aarch64.
I'm merging these patches into my `zstd-next` branch, which is pulled
into `linux-next` for further testing.

I've benchmarked BtrFS with zstd compression on a x86-64 machine, and
saw these results. Decompression speed is a small win across the board.
The lower compression levels 1-4 see both compression speed and
compression ratio wins. The higher compression levels see a small
compression speed loss and about neutral ratio. I expect the lower
compression levels to be used much more heavily than the high
compression levels, so this should be a net win.

Level	CTime	DTime	Ratio
1	-2.95%	-1.1%	-0.7%
3	-3.5%	-1.2%	-0.5%
5	+3.7%	-1.0%	+0.0%
7	+3.2%	-0.9%	+0.0%
9	-4.3%	-0.8%	+0.1%

Signed-off-by: Nick Terrell <terrelln@fb.com>

1 files changed, 57 insertions, 19 deletions

diff --git a/lib/zstd/compress/zstd_ldm.c b/lib/zstd/compress/zstd_ldm.c
index 8ef7e88a5add..dd86fc83e7dd 100644
--- a/lib/zstd/compress/zstd_ldm.c
+++ b/lib/zstd/compress/zstd_ldm.c
@@ -57,6 +57,33 @@ static void ZSTD_ldm_gear_init(ldmRollingHashState_t* state, ldmParams_t const*
     }
 }
 
+/* ZSTD_ldm_gear_reset()
+ * Feeds [data, data + minMatchLength) into the hash without registering any
+ * splits. This effectively resets the hash state. This is used when skipping
+ * over data, either at the beginning of a block, or skipping sections.
+ */
+static void ZSTD_ldm_gear_reset(ldmRollingHashState_t* state,
+                                BYTE const* data, size_t minMatchLength)
+{
+    U64 hash = state->rolling;
+    size_t n = 0;
+
+#define GEAR_ITER_ONCE() do {                                  \
+        hash = (hash << 1) + ZSTD_ldm_gearTab[data[n] & 0xff]; \
+        n += 1;                                                \
+    } while (0)
+    while (n + 3 < minMatchLength) {
+        GEAR_ITER_ONCE();
+        GEAR_ITER_ONCE();
+        GEAR_ITER_ONCE();
+        GEAR_ITER_ONCE();
+    }
+    while (n < minMatchLength) {
+        GEAR_ITER_ONCE();
+    }
+#undef GEAR_ITER_ONCE
+}
+
 /* ZSTD_ldm_gear_feed():
  *
  * Registers in the splits array all the split points found in the first
@@ -132,12 +159,12 @@ size_t ZSTD_ldm_getTableSize(ldmParams_t params)
     size_t const ldmBucketSize = ((size_t)1) << (params.hashLog - ldmBucketSizeLog);
     size_t const totalSize = ZSTD_cwksp_alloc_size(ldmBucketSize)
                            + ZSTD_cwksp_alloc_size(ldmHSize * sizeof(ldmEntry_t));
-    return params.enableLdm ? totalSize : 0;
+    return params.enableLdm == ZSTD_ps_enable ? totalSize : 0;
 }
 
 size_t ZSTD_ldm_getMaxNbSeq(ldmParams_t params, size_t maxChunkSize)
 {
-    return params.enableLdm ? (maxChunkSize / params.minMatchLength) : 0;
+    return params.enableLdm == ZSTD_ps_enable ? (maxChunkSize / params.minMatchLength) : 0;
 }
 
 /* ZSTD_ldm_getBucket() :
@@ -255,7 +282,7 @@ void ZSTD_ldm_fillHashTable(
     while (ip < iend) {
         size_t hashed;
         unsigned n;
-        
+
         numSplits = 0;
         hashed = ZSTD_ldm_gear_feed(&hashState, ip, iend - ip, splits, &numSplits);
 
@@ -327,16 +354,8 @@ static size_t ZSTD_ldm_generateSequences_internal(
 
     /* Initialize the rolling hash state with the first minMatchLength bytes */
     ZSTD_ldm_gear_init(&hashState, params);
-    {
-        size_t n = 0;
-
-        while (n < minMatchLength) {
-            numSplits = 0;
-            n += ZSTD_ldm_gear_feed(&hashState, ip + n, minMatchLength - n,
-                                    splits, &numSplits);
-        }
-        ip += minMatchLength;
-    }
+    ZSTD_ldm_gear_reset(&hashState, ip, minMatchLength);
+    ip += minMatchLength;
 
     while (ip < ilimit) {
         size_t hashed;
@@ -361,6 +380,7 @@ static size_t ZSTD_ldm_generateSequences_internal(
         for (n = 0; n < numSplits; n++) {
             size_t forwardMatchLength = 0, backwardMatchLength = 0,
                    bestMatchLength = 0, mLength;
+            U32 offset;
             BYTE const* const split = candidates[n].split;
             U32 const checksum = candidates[n].checksum;
             U32 const hash = candidates[n].hash;
@@ -428,9 +448,9 @@ static size_t ZSTD_ldm_generateSequences_internal(
             }
 
             /* Match found */
+            offset = (U32)(split - base) - bestEntry->offset;
             mLength = forwardMatchLength + backwardMatchLength;
             {
-                U32 const offset = (U32)(split - base) - bestEntry->offset;
                 rawSeq* const seq = rawSeqStore->seq + rawSeqStore->size;
 
                 /* Out of sequence storage */
@@ -447,6 +467,21 @@ static size_t ZSTD_ldm_generateSequences_internal(
             ZSTD_ldm_insertEntry(ldmState, hash, newEntry, *params);
 
             anchor = split + forwardMatchLength;
+
+            /* If we find a match that ends after the data that we've hashed
+             * then we have a repeating, overlapping, pattern. E.g. all zeros.
+             * If one repetition of the pattern matches our `stopMask` then all
+             * repetitions will. We don't need to insert them all into out table,
+             * only the first one. So skip over overlapping matches.
+             * This is a major speed boost (20x) for compressing a single byte
+             * repeated, when that byte ends up in the table.
+             */
+            if (anchor > ip + hashed) {
+                ZSTD_ldm_gear_reset(&hashState, anchor - minMatchLength, minMatchLength);
+                /* Continue the outer loop at anchor (ip + hashed == anchor). */
+                ip = anchor - hashed;
+                break;
+            }
         }
 
         ip += hashed;
@@ -500,7 +535,7 @@ size_t ZSTD_ldm_generateSequences(
 
         assert(chunkStart < iend);
         /* 1. Perform overflow correction if necessary. */
-        if (ZSTD_window_needOverflowCorrection(ldmState->window, chunkEnd)) {
+        if (ZSTD_window_needOverflowCorrection(ldmState->window, 0, maxDist, ldmState->loadedDictEnd, chunkStart, chunkEnd)) {
             U32 const ldmHSize = 1U << params->hashLog;
             U32 const correction = ZSTD_window_correctOverflow(
                 &ldmState->window, /* cycleLog */ 0, maxDist, chunkStart);
@@ -544,7 +579,9 @@ size_t ZSTD_ldm_generateSequences(
     return 0;
 }
 
-void ZSTD_ldm_skipSequences(rawSeqStore_t* rawSeqStore, size_t srcSize, U32 const minMatch) {
+void
+ZSTD_ldm_skipSequences(rawSeqStore_t* rawSeqStore, size_t srcSize, U32 const minMatch)
+{
     while (srcSize > 0 && rawSeqStore->pos < rawSeqStore->size) {
         rawSeq* seq = rawSeqStore->seq + rawSeqStore->pos;
         if (srcSize <= seq->litLength) {
@@ -622,12 +659,13 @@ void ZSTD_ldm_skipRawSeqStoreBytes(rawSeqStore_t* rawSeqStore, size_t nbBytes) {
 
 size_t ZSTD_ldm_blockCompress(rawSeqStore_t* rawSeqStore,
     ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
+    ZSTD_paramSwitch_e useRowMatchFinder,
     void const* src, size_t srcSize)
 {
     const ZSTD_compressionParameters* const cParams = &ms->cParams;
     unsigned const minMatch = cParams->minMatch;
     ZSTD_blockCompressor const blockCompressor =
-        ZSTD_selectBlockCompressor(cParams->strategy, ZSTD_matchState_dictMode(ms));
+        ZSTD_selectBlockCompressor(cParams->strategy, useRowMatchFinder, ZSTD_matchState_dictMode(ms));
     /* Input bounds */
     BYTE const* const istart = (BYTE const*)src;
     BYTE const* const iend = istart + srcSize;
@@ -673,8 +711,8 @@ size_t ZSTD_ldm_blockCompress(rawSeqStore_t* rawSeqStore,
             rep[0] = sequence.offset;
             /* Store the sequence */
             ZSTD_storeSeq(seqStore, newLitLength, ip - newLitLength, iend,
-                          sequence.offset + ZSTD_REP_MOVE,
-                          sequence.matchLength - MINMATCH);
+                          STORE_OFFSET(sequence.offset),
+                          sequence.matchLength);
             ip += sequence.matchLength;
         }
     }