erofs: tidy up stream decompressors

Just use a generic helper to prepare buffers for all supported
stream decompressors, eliminating similar logic.

Signed-off-by: Gao Xiang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: hsiangkao

fs/erofs/compress.h

@@ -88,6 +88,21 @@ extern const struct z_erofs_decompressor z_erofs_deflate_decomp;
 extern const struct z_erofs_decompressor z_erofs_zstd_decomp;
 extern const struct z_erofs_decompressor *z_erofs_decomp[];
 
+struct z_erofs_stream_dctx {
+	struct z_erofs_decompress_req *rq;
+	unsigned int inpages, outpages;	/* # of {en,de}coded pages */
+	int no, ni;			/* the current {en,de}coded page # */
+
+	unsigned int avail_out;		/* remaining bytes in the decoded buffer */
+	unsigned int inbuf_pos, inbuf_sz;
+					/* current status of the encoded buffer */
+	u8 *kin, *kout;			/* buffer mapped pointers */
+	void *bounce;			/* bounce buffer for inplace I/Os */
+	bool bounced;			/* is the bounce buffer used now? */
+};
+
+int z_erofs_stream_switch_bufs(struct z_erofs_stream_dctx *dctx, void **dst,
+			       void **src, struct page **pgpl);
 int z_erofs_fixup_insize(struct z_erofs_decompress_req *rq, const char *padbuf,
 			 unsigned int padbufsize);
 int __init z_erofs_init_decompressor(void);

fs/erofs/decompressor.c

@@ -372,6 +372,89 @@ static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq,
 	return 0;
 }
 
+int z_erofs_stream_switch_bufs(struct z_erofs_stream_dctx *dctx, void **dst,
+			       void **src, struct page **pgpl)
+{
+	struct z_erofs_decompress_req *rq = dctx->rq;
+	struct super_block *sb = rq->sb;
+	struct page **pgo, *tmppage;
+	unsigned int j;
+
+	if (!dctx->avail_out) {
+		if (++dctx->no >= dctx->outpages || !rq->outputsize) {
+			erofs_err(sb, "insufficient space for decompressed data");
+			return -EFSCORRUPTED;
+		}
+
+		if (dctx->kout)
+			kunmap_local(dctx->kout);
+		dctx->avail_out = min(rq->outputsize, PAGE_SIZE - rq->pageofs_out);
+		rq->outputsize -= dctx->avail_out;
+		pgo = &rq->out[dctx->no];
+		if (!*pgo && rq->fillgaps) {		/* deduped */
+			*pgo = erofs_allocpage(pgpl, rq->gfp);
+			if (!*pgo) {
+				dctx->kout = NULL;
+				return -ENOMEM;
+			}
+			set_page_private(*pgo, Z_EROFS_SHORTLIVED_PAGE);
+		}
+		if (*pgo) {
+			dctx->kout = kmap_local_page(*pgo);
+			*dst = dctx->kout + rq->pageofs_out;
+		} else {
+			*dst = dctx->kout = NULL;
+		}
+		rq->pageofs_out = 0;
+	}
+
+	if (dctx->inbuf_pos == dctx->inbuf_sz && rq->inputsize) {
+		if (++dctx->ni >= dctx->inpages) {
+			erofs_err(sb, "invalid compressed data");
+			return -EFSCORRUPTED;
+		}
+		if (dctx->kout) /* unlike kmap(), take care of the orders */
+			kunmap_local(dctx->kout);
+		kunmap_local(dctx->kin);
+
+		dctx->inbuf_sz = min_t(u32, rq->inputsize, PAGE_SIZE);
+		rq->inputsize -= dctx->inbuf_sz;
+		dctx->kin = kmap_local_page(rq->in[dctx->ni]);
+		*src = dctx->kin;
+		dctx->bounced = false;
+		if (dctx->kout) {
+			j = (u8 *)*dst - dctx->kout;
+			dctx->kout = kmap_local_page(rq->out[dctx->no]);
+			*dst = dctx->kout + j;
+		}
+		dctx->inbuf_pos = 0;
+	}
+
+	/*
+	 * Handle overlapping: Use the given bounce buffer if the input data is
+	 * under processing; Or utilize short-lived pages from the on-stack page
+	 * pool, where pages are shared among the same request.  Note that only
+	 * a few inplace I/O pages need to be doubled.
+	 */
+	if (!dctx->bounced && rq->out[dctx->no] == rq->in[dctx->ni]) {
+		memcpy(dctx->bounce, *src, dctx->inbuf_sz);
+		*src = dctx->bounce;
+		dctx->bounced = true;
+	}
+
+	for (j = dctx->ni + 1; j < dctx->inpages; ++j) {
+		if (rq->out[dctx->no] != rq->in[j])
+			continue;
+		tmppage = erofs_allocpage(pgpl, rq->gfp);
+		if (!tmppage)
+			return -ENOMEM;
+		set_page_private(tmppage, Z_EROFS_SHORTLIVED_PAGE);
+		copy_highpage(tmppage, rq->in[j]);
+		rq->in[j] = tmppage;
+	}
+	return 0;
+}
+
 const struct z_erofs_decompressor *z_erofs_decomp[] = {
 	[Z_EROFS_COMPRESSION_SHIFTED] = &(const struct z_erofs_decompressor) {
 		.decompress = z_erofs_transform_plain,

fs/erofs/decompressor_deflate.c

@@ -100,24 +100,23 @@ static int z_erofs_load_deflate_config(struct super_block *sb,
 static int z_erofs_deflate_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;
 	struct super_block *sb = rq->sb;
-	unsigned int insz, outsz, pofs;
+	struct z_erofs_stream_dctx dctx = {
+		.rq = rq,
+		.inpages = PAGE_ALIGN(rq->inputsize) >> PAGE_SHIFT,
+		.outpages = PAGE_ALIGN(rq->pageofs_out + rq->outputsize)
+				>> PAGE_SHIFT,
+		.no = -1, .ni = 0,
+	};
 	struct z_erofs_deflate *strm;
-	u8 *kin, *kout = NULL;
-	bool bounced = false;
-	int no = -1, ni = 0, j = 0, zerr, err;
+	int zerr, err;
 
 	/* 1. get the exact DEFLATE 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));
+	dctx.kin = kmap_local_page(*rq->in);
+	err = z_erofs_fixup_insize(rq, dctx.kin + rq->pageofs_in,
+			min(rq->inputsize, sb->s_blocksize - rq->pageofs_in));
 	if (err) {
-		kunmap_local(kin);
+		kunmap_local(dctx.kin);
 		return err;
 	}
 
@@ -134,116 +133,48 @@ static int z_erofs_deflate_decompress(struct z_erofs_decompress_req *rq,
 	spin_unlock(&z_erofs_deflate_lock);
 
 	/* 3. multi-call decompress */
-	insz = rq->inputsize;
-	outsz = rq->outputsize;
 	zerr = zlib_inflateInit2(&strm->z, -MAX_WBITS);
 	if (zerr != Z_OK) {
 		err = -EIO;
 		goto failed_zinit;
 	}
 
-	pofs = rq->pageofs_out;
-	strm->z.avail_in = min_t(u32, insz, PAGE_SIZE - rq->pageofs_in);
-	insz -= strm->z.avail_in;
-	strm->z.next_in = kin + rq->pageofs_in;
+	rq->fillgaps = true;	/* DEFLATE doesn't support NULL output buffer */
+	strm->z.avail_in = min(rq->inputsize, PAGE_SIZE - rq->pageofs_in);
+	rq->inputsize -= strm->z.avail_in;
+	strm->z.next_in = dctx.kin + rq->pageofs_in;
 	strm->z.avail_out = 0;
+	dctx.bounce = strm->bounce;
 
 	while (1) {
-		if (!strm->z.avail_out) {
-			if (++no >= nrpages_out || !outsz) {
-				erofs_err(sb, "insufficient space for decompressed data");
-				err = -EFSCORRUPTED;
-				break;
-			}
-
-			if (kout)
-				kunmap_local(kout);
-			strm->z.avail_out = min_t(u32, outsz, PAGE_SIZE - pofs);
-			outsz -= strm->z.avail_out;
-			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]);
-			strm->z.next_out = kout + pofs;
-			pofs = 0;
-		}
-
-		if (!strm->z.avail_in && insz) {
-			if (++ni >= nrpages_in) {
-				erofs_err(sb, "invalid compressed data");
-				err = -EFSCORRUPTED;
-				break;
-			}
-
-			if (kout) { /* unlike kmap(), take care of the orders */
-				j = strm->z.next_out - kout;
-				kunmap_local(kout);
-			}
-			kunmap_local(kin);
-			strm->z.avail_in = min_t(u32, insz, PAGE_SIZE);
-			insz -= strm->z.avail_in;
-			kin = kmap_local_page(rq->in[ni]);
-			strm->z.next_in = kin;
-			bounced = false;
-			if (kout) {
-				kout = kmap_local_page(rq->out[no]);
-				strm->z.next_out = 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, strm->z.next_in, strm->z.avail_in);
-			strm->z.next_in = 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;
-		}
+		dctx.avail_out = strm->z.avail_out;
+		dctx.inbuf_sz = strm->z.avail_in;
+		err = z_erofs_stream_switch_bufs(&dctx,
+					(void **)&strm->z.next_out,
+					(void **)&strm->z.next_in, pgpl);
+		if (err)
+			break;
+		strm->z.avail_out = dctx.avail_out;
+		strm->z.avail_in = dctx.inbuf_sz;
 
 		zerr = zlib_inflate(&strm->z, Z_SYNC_FLUSH);
-		if (zerr != Z_OK || !(outsz + strm->z.avail_out)) {
+		if (zerr != Z_OK || !(rq->outputsize + strm->z.avail_out)) {
 			if (zerr == Z_OK && rq->partial_decoding)
 				break;
-			if (zerr == Z_STREAM_END && !outsz)
+			if (zerr == Z_STREAM_END && !rq->outputsize)
 				break;
 			erofs_err(sb, "failed to decompress %d in[%u] out[%u]",
 				  zerr, rq->inputsize, rq->outputsize);
 			err = -EFSCORRUPTED;
 			break;
 		}
 	}
-failed:
 	if (zlib_inflateEnd(&strm->z) != Z_OK && !err)
 		err = -EIO;
-	if (kout)
-		kunmap_local(kout);
+	if (dctx.kout)
+		kunmap_local(dctx.kout);
 failed_zinit:
-	kunmap_local(kin);
+	kunmap_local(dctx.kin);
 	/* 4. push back DEFLATE stream context to the global list */
 	spin_lock(&z_erofs_deflate_lock);
 	strm->next = z_erofs_deflate_head;