Hi,
generic_forget_inode() don't call trancate_inode_pages() if FS is still active
see the 10449 line below:
1040 static void generic_forget_inode(struct inode *inode)
1041 {
1042 struct super_block *sb = inode->i_sb;
1043
1044 if (!hlist_unhashed(&inode->i_hash)) {
1045 if (!(inode->i_state & (I_DIRTY|I_LOCK)))
1046 list_move(&inode->i_list, &inode_unused);
1047 inodes_stat.nr_unused++;
1048 spin_unlock(&inode_lock);
1049 if (!sb || (sb->s_flags & MS_ACTIVE))
1050 return;
1051 write_inode_now(inode, 1);
1052 spin_lock(&inode_lock);
1053 inodes_stat.nr_unused--;
1054 hlist_del_init(&inode->i_hash);
1055 }
1056 list_del_init(&inode->i_list);
1057 list_del_init(&inode->i_sb_list);
1058 inode->i_state|=I_FREEING;
1059 inodes_stat.nr_inodes--;
1060 spin_unlock(&inode_lock);
1061 if (inode->i_data.nrpages)
1062 truncate_inode_pages(&inode->i_data, 0);
1063 clear_inode(inode);
1064 destroy_inode(inode);
1065
On 3/28/07, Xin Zhao <uszhaoxin@xxxxxxxxx> wrote:
Hi,
If a Linux process opens and reads a file A, then it closes the file.
Will Linux keep the file A's data in cache for a while in case another
process opens and reads the same in a short time? I think that is what
I heard before.
But after I digged into the kernel code, I am confused.
When a process closes the file A, iput() will be called, which in turn
calls the follows two functions:
iput_final()->generic_drop_inode()
But from the following calling chain, we can see that file close will
eventually lead to evict and free all cached pages. Actually in
truncate_complete_page(), the pages will be freed. This seems to
imply that Linux has to re-read the same data from disk even if
another process B read the same file right after process A closes the
file. That does not make sense to me.
/***calling chain ***/
generic_delete_inode/generic_forget_inode()->
truncate_inode_pages()->truncate_inode_pages_range()->
truncate_complete_page()->remove_from_page_cache()->
__remove_from_page_cache()->radix_tree_delete()
Am I missing something? Can someone please provide some advise?
Thanks a lot
-x
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