Re: [PATCH] fs: warn if stale pagecache is left after direct write

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On 30/10/2019 03.20, kbuild test robot wrote:
Hi Konstantin,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v5.4-rc5 next-20191029]
[if your patch is applied to the wrong git tree, please drop us a note to help
improve the system. BTW, we also suggest to use '--base' option to specify the
base tree in git format-patch, please see https://stackoverflow.com/a/37406982]

url:    https://github.com/0day-ci/linux/commits/Konstantin-Khlebnikov/fs-warn-if-stale-pagecache-is-left-after-direct-write/20191030-073543
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 23fdb198ae81f47a574296dab5167c5e136a02ba
config: i386-tinyconfig (attached as .config)
compiler: gcc-7 (Debian 7.4.0-14) 7.4.0
reproduce:
         # save the attached .config to linux build tree
         make ARCH=i386

If you fix the issue, kindly add following tag
Reported-by: kbuild test robot <lkp@xxxxxxxxx>

All errors (new ones prefixed by >>):

    mm/filemap.c: In function 'generic_file_direct_write':
mm/filemap.c:3229:3: error: implicit declaration of function 'dio_warn_stale_pagecache'; did you mean 'truncate_pagecache'? [-Werror=implicit-function-declaration]
       dio_warn_stale_pagecache(file);
       ^~~~~~~~~~~~~~~~~~~~~~~~
       truncate_pagecache
    cc1: some warnings being treated as errors

This config has CONFIG_BLOCK=n while O_DIRECT is still here.
For example, NFS has it too.

I'll move dio_warn_stale_pagecache() into different file.


vim +3229 mm/filemap.c

   3163	
   3164	ssize_t
   3165	generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
   3166	{
   3167		struct file	*file = iocb->ki_filp;
   3168		struct address_space *mapping = file->f_mapping;
   3169		struct inode	*inode = mapping->host;
   3170		loff_t		pos = iocb->ki_pos;
   3171		ssize_t		written;
   3172		size_t		write_len;
   3173		pgoff_t		end;
   3174	
   3175		write_len = iov_iter_count(from);
   3176		end = (pos + write_len - 1) >> PAGE_SHIFT;
   3177	
   3178		if (iocb->ki_flags & IOCB_NOWAIT) {
   3179			/* If there are pages to writeback, return */
   3180			if (filemap_range_has_page(inode->i_mapping, pos,
   3181						   pos + write_len - 1))
   3182				return -EAGAIN;
   3183		} else {
   3184			written = filemap_write_and_wait_range(mapping, pos,
   3185								pos + write_len - 1);
   3186			if (written)
   3187				goto out;
   3188		}
   3189	
   3190		/*
   3191		 * After a write we want buffered reads to be sure to go to disk to get
   3192		 * the new data.  We invalidate clean cached page from the region we're
   3193		 * about to write.  We do this *before* the write so that we can return
   3194		 * without clobbering -EIOCBQUEUED from ->direct_IO().
   3195		 */
   3196		written = invalidate_inode_pages2_range(mapping,
   3197						pos >> PAGE_SHIFT, end);
   3198		/*
   3199		 * If a page can not be invalidated, return 0 to fall back
   3200		 * to buffered write.
   3201		 */
   3202		if (written) {
   3203			if (written == -EBUSY)
   3204				return 0;
   3205			goto out;
   3206		}
   3207	
   3208		written = mapping->a_ops->direct_IO(iocb, from);
   3209	
   3210		/*
   3211		 * Finally, try again to invalidate clean pages which might have been
   3212		 * cached by non-direct readahead, or faulted in by get_user_pages()
   3213		 * if the source of the write was an mmap'ed region of the file
   3214		 * we're writing.  Either one is a pretty crazy thing to do,
   3215		 * so we don't support it 100%.  If this invalidation
   3216		 * fails, tough, the write still worked...
   3217		 *
   3218		 * Most of the time we do not need this since dio_complete() will do
   3219		 * the invalidation for us. However there are some file systems that
   3220		 * do not end up with dio_complete() being called, so let's not break
   3221		 * them by removing it completely.
   3222		 *
   3223		 * Noticeable case is a blkdev_direct_IO().
   3224		 *
   3225		 * Skip invalidation for async writes or if mapping has no pages.
   3226		 */
   3227		if (written > 0 && mapping->nrpages &&
   3228		    invalidate_inode_pages2_range(mapping, pos >> PAGE_SHIFT, end))
3229			dio_warn_stale_pagecache(file);
   3230	
   3231		if (written > 0) {
   3232			pos += written;
   3233			write_len -= written;
   3234			if (pos > i_size_read(inode) && !S_ISBLK(inode->i_mode)) {
   3235				i_size_write(inode, pos);
   3236				mark_inode_dirty(inode);
   3237			}
   3238			iocb->ki_pos = pos;
   3239		}
   3240		iov_iter_revert(from, write_len - iov_iter_count(from));
   3241	out:
   3242		return written;
   3243	}
   3244	EXPORT_SYMBOL(generic_file_direct_write);
   3245	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation




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