__block_commit_write的疑问。。。

chishanmingshen

1. static int __block_commit_write(struct inode *inode, struct page *page,
   
2.         unsigned from, unsigned to)
   
3. {
   
4.     unsigned block_start, block_end;
   
5.     int partial = 0;
   
6.     unsigned blocksize;
   
7.     struct buffer_head *bh, *head;
   
8. 
   
9.     bh = head = page_buffers(page);
   
10.     blocksize = bh->b_size;
    
11. 
    
12.     block_start = 0;
    
13.     do {
    
14.         block_end = block_start + blocksize;
    
15.         if (block_end <= from || block_start >= to) {//分支1
    
16.             if (!buffer_uptodate(bh))
    
17.                 partial = 1;
    
18.         } else {//分支2
    
19.             set_buffer_uptodate(bh);
    
20.             mark_buffer_dirty(bh);
    
21.         }
    
22.         clear_buffer_new(bh);<---------为何不涉及的bh（分支1）也清new标志了？
    
23. 
    
24.         block_start = block_end;
    
25.         bh = bh->b_this_page;
    
26.     } while (bh != head);
    
27. 
    
28.     /*
    
29.      * If this is a partial write which happened to make all buffers
    
30.      * uptodate then we can optimize away a bogus readpage() for
    
31.      * the next read(). Here we 'discover' whether the page went
    
32.      * uptodate as a result of this (potentially partial) write.
    
33.      */
    
34.     if (!partial)
    
35.         SetPageUptodate(page);
    
36.     return 0;
    
37. }
    

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望大家指点啊，谢谢！

humjb_1983

个人理解，在提交之后，new标记应该没有存在的意义了~

chishanmingshen

回复 2# humjb_1983


    是的。