btrfs: move some zstd work data from stack to workspace

* ZSTD_inBuffer in_buf
* ZSTD_outBuffer out_buf

are used in all functions to pass the compression parameters and the
local variables consume some space. We can move them to the workspace
and reduce the stack consumption:

zstd.c:zstd_decompress                        -24 (136 -> 112)
zstd.c:zstd_decompress_bio                    -24 (144 -> 120)
zstd.c:zstd_compress_pages                    -24 (264 -> 240)

Signed-off-by: David Sterba <dsterba@suse.com>
Reviewed-by: Nick Terrell <terrelln@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/zstd.c b/fs/btrfs/zstd.c
index 17f2dd8fddb8140829dd3a174ed5e57a1f3ce4d6..01a4eab602a3a72d216d71ed91829bd63459e136 100644 (file)
--- a/fs/btrfs/zstd.c
+++ b/fs/btrfs/zstd.c
@@ -43,6 +43,8 @@ struct workspace {
        size_t size;
        char *buf;
        struct list_head list;
+       ZSTD_inBuffer in_buf;
+       ZSTD_outBuffer out_buf;
 };
 
 static void zstd_free_workspace(struct list_head *ws)
@@ -94,8 +96,6 @@ static int zstd_compress_pages(struct list_head *ws,
        int nr_pages = 0;
        struct page *in_page = NULL;  /* The current page to read */
        struct page *out_page = NULL; /* The current page to write to */
-       ZSTD_inBuffer in_buf = { NULL, 0, 0 };
-       ZSTD_outBuffer out_buf = { NULL, 0, 0 };
        unsigned long tot_in = 0;
        unsigned long tot_out = 0;
        unsigned long len = *total_out;
@@ -118,9 +118,9 @@ static int zstd_compress_pages(struct list_head *ws,
 
        /* map in the first page of input data */
        in_page = find_get_page(mapping, start >> PAGE_SHIFT);
-       in_buf.src = kmap(in_page);
-       in_buf.pos = 0;
-       in_buf.size = min_t(size_t, len, PAGE_SIZE);
+       workspace->in_buf.src = kmap(in_page);
+       workspace->in_buf.pos = 0;
+       workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE);
 
 
        /* Allocate and map in the output buffer */
@@ -130,14 +130,15 @@ static int zstd_compress_pages(struct list_head *ws,
                goto out;
        }
        pages[nr_pages++] = out_page;
-       out_buf.dst = kmap(out_page);
-       out_buf.pos = 0;
-       out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
+       workspace->out_buf.dst = kmap(out_page);
+       workspace->out_buf.pos = 0;
+       workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
 
        while (1) {
                size_t ret2;
 
-               ret2 = ZSTD_compressStream(stream, &out_buf, &in_buf);
+               ret2 = ZSTD_compressStream(stream, &workspace->out_buf,
+                               &workspace->in_buf);
                if (ZSTD_isError(ret2)) {
                        pr_debug("BTRFS: ZSTD_compressStream returned %d\n",
                                        ZSTD_getErrorCode(ret2));
@@ -146,22 +147,22 @@ static int zstd_compress_pages(struct list_head *ws,
                }
 
                /* Check to see if we are making it bigger */
-               if (tot_in + in_buf.pos > 8192 &&
-                               tot_in + in_buf.pos <
-                               tot_out + out_buf.pos) {
+               if (tot_in + workspace->in_buf.pos > 8192 &&
+                               tot_in + workspace->in_buf.pos <
+                               tot_out + workspace->out_buf.pos) {
                        ret = -E2BIG;
                        goto out;
                }
 
                /* We've reached the end of our output range */
-               if (out_buf.pos >= max_out) {
-                       tot_out += out_buf.pos;
+               if (workspace->out_buf.pos >= max_out) {
+                       tot_out += workspace->out_buf.pos;
                        ret = -E2BIG;
                        goto out;
                }
 
                /* Check if we need more output space */
-               if (out_buf.pos == out_buf.size) {
+               if (workspace->out_buf.pos == workspace->out_buf.size) {
                        tot_out += PAGE_SIZE;
                        max_out -= PAGE_SIZE;
                        kunmap(out_page);
@@ -176,19 +177,20 @@ static int zstd_compress_pages(struct list_head *ws,
                                goto out;
                        }
                        pages[nr_pages++] = out_page;
-                       out_buf.dst = kmap(out_page);
-                       out_buf.pos = 0;
-                       out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
+                       workspace->out_buf.dst = kmap(out_page);
+                       workspace->out_buf.pos = 0;
+                       workspace->out_buf.size = min_t(size_t, max_out,
+                                                       PAGE_SIZE);
                }
 
                /* We've reached the end of the input */
-               if (in_buf.pos >= len) {
-                       tot_in += in_buf.pos;
+               if (workspace->in_buf.pos >= len) {
+                       tot_in += workspace->in_buf.pos;
                        break;
                }
 
                /* Check if we need more input */
-               if (in_buf.pos == in_buf.size) {
+               if (workspace->in_buf.pos == workspace->in_buf.size) {
                        tot_in += PAGE_SIZE;
                        kunmap(in_page);
                        put_page(in_page);
@@ -196,15 +198,15 @@ static int zstd_compress_pages(struct list_head *ws,
                        start += PAGE_SIZE;
                        len -= PAGE_SIZE;
                        in_page = find_get_page(mapping, start >> PAGE_SHIFT);
-                       in_buf.src = kmap(in_page);
-                       in_buf.pos = 0;
-                       in_buf.size = min_t(size_t, len, PAGE_SIZE);
+                       workspace->in_buf.src = kmap(in_page);
+                       workspace->in_buf.pos = 0;
+                       workspace->in_buf.size = min_t(size_t, len, PAGE_SIZE);
                }
        }
        while (1) {
                size_t ret2;
 
-               ret2 = ZSTD_endStream(stream, &out_buf);
+               ret2 = ZSTD_endStream(stream, &workspace->out_buf);
                if (ZSTD_isError(ret2)) {
                        pr_debug("BTRFS: ZSTD_endStream returned %d\n",
                                        ZSTD_getErrorCode(ret2));
@@ -212,11 +214,11 @@ static int zstd_compress_pages(struct list_head *ws,
                        goto out;
                }
                if (ret2 == 0) {
-                       tot_out += out_buf.pos;
+                       tot_out += workspace->out_buf.pos;
                        break;
                }
-               if (out_buf.pos >= max_out) {
-                       tot_out += out_buf.pos;
+               if (workspace->out_buf.pos >= max_out) {
+                       tot_out += workspace->out_buf.pos;
                        ret = -E2BIG;
                        goto out;
                }
@@ -235,9 +237,9 @@ static int zstd_compress_pages(struct list_head *ws,
                        goto out;
                }
                pages[nr_pages++] = out_page;
-               out_buf.dst = kmap(out_page);
-               out_buf.pos = 0;
-               out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
+               workspace->out_buf.dst = kmap(out_page);
+               workspace->out_buf.pos = 0;
+               workspace->out_buf.size = min_t(size_t, max_out, PAGE_SIZE);
        }
 
        if (tot_out >= tot_in) {
@@ -273,8 +275,6 @@ static int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
        unsigned long total_pages_in = DIV_ROUND_UP(srclen, PAGE_SIZE);
        unsigned long buf_start;
        unsigned long total_out = 0;
-       ZSTD_inBuffer in_buf = { NULL, 0, 0 };
-       ZSTD_outBuffer out_buf = { NULL, 0, 0 };
 
        stream = ZSTD_initDStream(
                        ZSTD_BTRFS_MAX_INPUT, workspace->mem, workspace->size);
@@ -284,18 +284,19 @@ static int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
                goto done;
        }
 
-       in_buf.src = kmap(pages_in[page_in_index]);
-       in_buf.pos = 0;
-       in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
+       workspace->in_buf.src = kmap(pages_in[page_in_index]);
+       workspace->in_buf.pos = 0;
+       workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
 
-       out_buf.dst = workspace->buf;
-       out_buf.pos = 0;
-       out_buf.size = PAGE_SIZE;
+       workspace->out_buf.dst = workspace->buf;
+       workspace->out_buf.pos = 0;
+       workspace->out_buf.size = PAGE_SIZE;
 
        while (1) {
                size_t ret2;
 
-               ret2 = ZSTD_decompressStream(stream, &out_buf, &in_buf);
+               ret2 = ZSTD_decompressStream(stream, &workspace->out_buf,
+                               &workspace->in_buf);
                if (ZSTD_isError(ret2)) {
                        pr_debug("BTRFS: ZSTD_decompressStream returned %d\n",
                                        ZSTD_getErrorCode(ret2));
@@ -303,38 +304,38 @@ static int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
                        goto done;
                }
                buf_start = total_out;
-               total_out += out_buf.pos;
-               out_buf.pos = 0;
+               total_out += workspace->out_buf.pos;
+               workspace->out_buf.pos = 0;
 
-               ret = btrfs_decompress_buf2page(out_buf.dst, buf_start,
-                               total_out, disk_start, orig_bio);
+               ret = btrfs_decompress_buf2page(workspace->out_buf.dst,
+                               buf_start, total_out, disk_start, orig_bio);
                if (ret == 0)
                        break;
 
-               if (in_buf.pos >= srclen)
+               if (workspace->in_buf.pos >= srclen)
                        break;
 
                /* Check if we've hit the end of a frame */
                if (ret2 == 0)
                        break;
 
-               if (in_buf.pos == in_buf.size) {
+               if (workspace->in_buf.pos == workspace->in_buf.size) {
                        kunmap(pages_in[page_in_index++]);
                        if (page_in_index >= total_pages_in) {
-                               in_buf.src = NULL;
+                               workspace->in_buf.src = NULL;
                                ret = -EIO;
                                goto done;
                        }
                        srclen -= PAGE_SIZE;
-                       in_buf.src = kmap(pages_in[page_in_index]);
-                       in_buf.pos = 0;
-                       in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
+                       workspace->in_buf.src = kmap(pages_in[page_in_index]);
+                       workspace->in_buf.pos = 0;
+                       workspace->in_buf.size = min_t(size_t, srclen, PAGE_SIZE);
                }
        }
        ret = 0;
        zero_fill_bio(orig_bio);
 done:
-       if (in_buf.src)
+       if (workspace->in_buf.src)
                kunmap(pages_in[page_in_index]);
        return ret;
 }
@@ -348,8 +349,6 @@ static int zstd_decompress(struct list_head *ws, unsigned char *data_in,
        ZSTD_DStream *stream;
        int ret = 0;
        size_t ret2;
-       ZSTD_inBuffer in_buf = { NULL, 0, 0 };
-       ZSTD_outBuffer out_buf = { NULL, 0, 0 };
        unsigned long total_out = 0;
        unsigned long pg_offset = 0;
        char *kaddr;
@@ -364,16 +363,17 @@ static int zstd_decompress(struct list_head *ws, unsigned char *data_in,
 
        destlen = min_t(size_t, destlen, PAGE_SIZE);
 
-       in_buf.src = data_in;
-       in_buf.pos = 0;
-       in_buf.size = srclen;
+       workspace->in_buf.src = data_in;
+       workspace->in_buf.pos = 0;
+       workspace->in_buf.size = srclen;
 
-       out_buf.dst = workspace->buf;
-       out_buf.pos = 0;
-       out_buf.size = PAGE_SIZE;
+       workspace->out_buf.dst = workspace->buf;
+       workspace->out_buf.pos = 0;
+       workspace->out_buf.size = PAGE_SIZE;
 
        ret2 = 1;
-       while (pg_offset < destlen && in_buf.pos < in_buf.size) {
+       while (pg_offset < destlen
+              && workspace->in_buf.pos < workspace->in_buf.size) {
                unsigned long buf_start;
                unsigned long buf_offset;
                unsigned long bytes;
@@ -384,7 +384,8 @@ static int zstd_decompress(struct list_head *ws, unsigned char *data_in,
                        ret = -EIO;
                        goto finish;
                }
-               ret2 = ZSTD_decompressStream(stream, &out_buf, &in_buf);
+               ret2 = ZSTD_decompressStream(stream, &workspace->out_buf,
+                               &workspace->in_buf);
                if (ZSTD_isError(ret2)) {
                        pr_debug("BTRFS: ZSTD_decompressStream returned %d\n",
                                        ZSTD_getErrorCode(ret2));
@@ -393,8 +394,8 @@ static int zstd_decompress(struct list_head *ws, unsigned char *data_in,
                }
 
                buf_start = total_out;
-               total_out += out_buf.pos;
-               out_buf.pos = 0;
+               total_out += workspace->out_buf.pos;
+               workspace->out_buf.pos = 0;
 
                if (total_out <= start_byte)
                        continue;
@@ -405,10 +406,11 @@ static int zstd_decompress(struct list_head *ws, unsigned char *data_in,
                        buf_offset = 0;
 
                bytes = min_t(unsigned long, destlen - pg_offset,
-                               out_buf.size - buf_offset);
+                               workspace->out_buf.size - buf_offset);
 
                kaddr = kmap_atomic(dest_page);
-               memcpy(kaddr + pg_offset, out_buf.dst + buf_offset, bytes);
+               memcpy(kaddr + pg_offset, workspace->out_buf.dst + buf_offset,
+                               bytes);
                kunmap_atomic(kaddr);
 
                pg_offset += bytes;