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Date: Wed, 30 Oct 2019 11:09:06 +0300
From: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To: kbuild test robot <lkp@...el.com>
Cc: kbuild-all@...ts.01.org, linux-mm@...ck.org,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org,
Alexander Viro <viro@...iv.linux.org.uk>,
linux-fsdevel@...r.kernel.org, Jan Kara <jack@...e.cz>
Subject: Re: [PATCH] fs: warn if stale pagecache is left after direct write
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@...el.com>
>
> 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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