Re: [f2fs-dev] [RFC PATCH] f2fs: compress: reduce one page array alloc and free when write compressed page

[Fengnan Chang]

Sorry, I didn't get your point, in my opinion, new_nr_cpages should 
always little than nr_cpages, is this right? So we can just use cpages, 
don't need to alloc new one.

Thanks.

On 2021/7/22 21:53, Chao Yu wrote:
On 2021/7/22 11:47, Fengnan Chang wrote:
Don't alloc new page array to replace old, just use old page array, try
to reduce one page array alloc and free when write compress page.

Nope, see whole story in below link:

https://lore.kernel.org/patchwork/patch/1305096/

Thanks,


Signed-off-by: Fengnan Chang <changfeng...@vivo.com>
---
  fs/f2fs/compress.c | 14 ++------------
  fs/f2fs/f2fs.h     |  1 +
  2 files changed, 3 insertions(+), 12 deletions(-)

diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
index 455561826c7d..43daafe382e7 100644
--- a/fs/f2fs/compress.c
+++ b/fs/f2fs/compress.c
@@ -618,7 +618,6 @@ static int f2fs_compress_pages(struct compress_ctx 
*cc)
      const struct f2fs_compress_ops *cops =
                  f2fs_cops[fi->i_compress_algorithm];
      unsigned int max_len, new_nr_cpages;
-    struct page **new_cpages;
      u32 chksum = 0;
      int i, ret;
@@ -633,6 +632,7 @@ static int f2fs_compress_pages(struct compress_ctx 
*cc)
      max_len = COMPRESS_HEADER_SIZE + cc->clen;
      cc->nr_cpages = DIV_ROUND_UP(max_len, PAGE_SIZE);
+    cc->raw_nr_cpages = cc->nr_cpages;
      cc->cpages = page_array_alloc(cc->inode, cc->nr_cpages);
      if (!cc->cpages) {
@@ -683,13 +683,6 @@ static int f2fs_compress_pages(struct 
compress_ctx *cc)
      new_nr_cpages = DIV_ROUND_UP(cc->clen + COMPRESS_HEADER_SIZE, 
PAGE_SIZE);
-    /* Now we're going to cut unnecessary tail pages */
-    new_cpages = page_array_alloc(cc->inode, new_nr_cpages);
-    if (!new_cpages) {
-        ret = -ENOMEM;
-        goto out_vunmap_cbuf;
-    }
-
      /* zero out any unused part of the last page */
      memset(&cc->cbuf->cdata[cc->clen], 0,
              (new_nr_cpages * PAGE_SIZE) -
@@ -700,7 +693,6 @@ static int f2fs_compress_pages(struct compress_ctx 
*cc)
      for (i = 0; i < cc->nr_cpages; i++) {
          if (i < new_nr_cpages) {
-            new_cpages[i] = cc->cpages[i];
              continue;
          }
          f2fs_compress_free_page(cc->cpages[i]);
@@ -710,8 +702,6 @@ static int f2fs_compress_pages(struct compress_ctx 
*cc)
      if (cops->destroy_compress_ctx)
          cops->destroy_compress_ctx(cc);
-    page_array_free(cc->inode, cc->cpages, cc->nr_cpages);
-    cc->cpages = new_cpages;
      cc->nr_cpages = new_nr_cpages;
      trace_f2fs_compress_pages_end(cc->inode, cc->cluster_idx,
@@ -1330,7 +1320,7 @@ static int f2fs_write_compressed_pages(struct 
compress_ctx *cc,
      spin_unlock(&fi->i_size_lock);
      f2fs_put_rpages(cc);
-    page_array_free(cc->inode, cc->cpages, cc->nr_cpages);
+    page_array_free(cc->inode, cc->cpages, cc->raw_nr_cpages);
      cc->cpages = NULL;
      f2fs_destroy_compress_ctx(cc, false);
      return 0;
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 867f2c5d9559..8b1f84d88a65 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1454,6 +1454,7 @@ struct compress_ctx {
      unsigned int nr_rpages;        /* total page number in rpages */
      struct page **cpages;        /* pages store compressed data in 
cluster */
      unsigned int nr_cpages;        /* total page number in cpages */
+    unsigned int raw_nr_cpages;    /* max total page number in cpages */
      void *rbuf;            /* virtual mapped address on rpages */
      struct compress_data *cbuf;    /* virtual mapped address on 
cpages */
      size_t rlen;            /* valid data length in rbuf */




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