Re: [f2fs-dev] [PATCH 2/2] f2fs: support POSIX_FADV_DONTNEED drop compressed page cache

Thu, 25 Nov 2021 18:59:00 -0800 

On 2021/11/26 10:14, 常凤楠 wrote:




-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Chao
Yu
Sent: Thursday, November 25, 2021 11:15 PM
To: 常凤楠 <[email protected]>; [email protected]
Cc: [email protected]
Subject: Re: [PATCH 2/2] f2fs: support POSIX_FADV_DONTNEED drop
compressed page cache

On 2021/11/24 16:39, Fengnan Chang wrote:

Previously, compressed page cache drop when clean page cache, but
POSIX_FADV_DONTNEED can't clean compressed page cache, this commit try
to support it.

Signed-off-by: Fengnan Chang <[email protected]>
---
   fs/f2fs/compress.c | 10 ++++++++--
   fs/f2fs/f2fs.h     |  7 ++++---
   2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c index
fb9e5149af5d..7ec5e3c2590b 100644
--- a/fs/f2fs/compress.c
+++ b/fs/f2fs/compress.c
@@ -842,7 +842,7 @@ void f2fs_end_read_compressed_page(struct page

*page, bool failed,

                WRITE_ONCE(dic->failed, true);
        else if (blkaddr)
                f2fs_cache_compressed_page(sbi, page,
-                                       dic->inode->i_ino, blkaddr);
+                                       dic, blkaddr);

        if (atomic_dec_and_test(&dic->remaining_pages))
                f2fs_decompress_cluster(dic);
@@ -1659,6 +1659,7 @@ static void f2fs_put_dic(struct decompress_io_ctx

*dic)

   static void __f2fs_decompress_end_io(struct decompress_io_ctx *dic, bool

failed)

   {
        int i;
+       nid_t ino = dic->inode->i_ino;

        for (i = 0; i < dic->cluster_size; i++) {
                struct page *rpage = dic->rpages[i]; @@ -1666,6 +1667,9 @@

static

void __f2fs_decompress_end_io(struct decompress_io_ctx *dic, bool failed)
                if (!rpage)
                        continue;

+               if (dic->cpage_cached)
+                       set_page_private_data(rpage, ino);


I didn't get the point, why should we set ino into raw page's private field?

Yes, because raw page will add into page cache, and
POSIX_FADV_DONTNEED:
invalidate_mapping_pagevec
   ->__invalidate_mapping_pages
     ->invalidate_inode_page
       ->invalidate_complete_page  // call try_to_release_page when page has 
private data

So, if raw page don't have private data, it will not call 
f2fs_invalidate_compress_pages.
This commit try use private data to connect raw page which compressed page has 
been cached.


Oh, yup, how about calling f2fs_invalidate_compress_pages() directly in 
f2fs_file_fadvise()
for POSIX_FADV_DONTNEED case? it can avoid unneeded use of private field space.

Thanks,


  


Thanks,


+
                /* PG_error was set if verity failed. */
                if (failed || PageError(rpage)) {
                        ClearPageUptodate(rpage);
@@ -1772,10 +1776,11 @@ void f2fs_invalidate_compress_page(struct

f2fs_sb_info *sbi, block_t blkaddr)

   }

   void f2fs_cache_compressed_page(struct f2fs_sb_info *sbi, struct page

*page,

-                                               nid_t ino, block_t blkaddr)
+                               struct decompress_io_ctx *dic, block_t blkaddr)
   {
        struct page *cpage;
        int ret;
+       nid_t ino = dic->inode->i_ino;

        if (!test_opt(sbi, COMPRESS_CACHE))
                return;
@@ -1804,6 +1809,7 @@ void f2fs_cache_compressed_page(struct

f2fs_sb_info *sbi, struct page *page,

        }

        set_page_private_data(cpage, ino);
+       dic->cpage_cached = true;

        if (!f2fs_is_valid_blkaddr(sbi, blkaddr,

DATA_GENERIC_ENHANCE_READ))

                goto out;
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h index
ac6dda6c4c5a..128190b0c737 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1551,6 +1551,7 @@ struct decompress_io_ctx {
         */
        refcount_t refcnt;

+       bool cpage_cached;              /* indicate cpages cached in compress

mapping*/

        bool failed;                    /* IO error occurred before 
decompression?

*/

        bool need_verity;               /* need fs-verity verification after

decompression? */

        void *private;                  /* payload buffer for specified

decompression algorithm */

@@ -4085,7 +4086,7 @@ void f2fs_destroy_compress_cache(void);
   struct address_space *COMPRESS_MAPPING(struct f2fs_sb_info *sbi);
   void f2fs_invalidate_compress_page(struct f2fs_sb_info *sbi, block_t

blkaddr);

   void f2fs_cache_compressed_page(struct f2fs_sb_info *sbi, struct page

*page,

-                                               nid_t ino, block_t blkaddr);
+                               struct decompress_io_ctx *dic, block_t blkaddr);
   bool f2fs_load_compressed_page(struct f2fs_sb_info *sbi, struct page

*page,

                                                                block_t 
blkaddr);
   void f2fs_invalidate_compress_pages(struct f2fs_sb_info *sbi, nid_t
ino); @@ -4137,8 +4138,8 @@ static inline int __init

f2fs_init_compress_cache(void) { return 0; }

   static inline void f2fs_destroy_compress_cache(void) { }
   static inline void f2fs_invalidate_compress_page(struct f2fs_sb_info *sbi,
                                block_t blkaddr) { }
-static inline void f2fs_cache_compressed_page(struct f2fs_sb_info *sbi,
-                               struct page *page, nid_t ino, block_t blkaddr) 
{ }
+static inline void f2fs_cache_compressed_page(struct f2fs_sb_info *sbi,

struct page *page,

+                               struct decompress_io_ctx *dic, block_t blkaddr) 
{ }
   static inline bool f2fs_load_compressed_page(struct f2fs_sb_info *sbi,
                                struct page *page, block_t blkaddr) { return 
false; }
   static inline void f2fs_invalidate_compress_pages(struct
f2fs_sb_info *sbi,




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