Re: [PATCH 1/3] afs: Handle len being extending over page end in write_begin/write_end

From: kernel test robot
Date: Thu Jun 17 2021 - 03:43:21 EST

Hi David,

I love your patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v5.13-rc6 next-20210616]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url: https://github.com/0day-ci/linux/commits/David-Howells/afs-Handle-len-being-extending-over-page-end-in-write_begin-write_end/20210617-091000
base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 70585216fe7730d9fb5453d3e2804e149d0fe201
config: arc-allyesconfig (attached as .config)
compiler: arceb-elf-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://github.com/0day-ci/linux/commit/d5cb85d0ca85764a811baaf4baca5f1890476434
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review David-Howells/afs-Handle-len-being-extending-over-page-end-in-write_begin-write_end/20210617-091000
git checkout d5cb85d0ca85764a811baaf4baca5f1890476434
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=arc

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

All warnings (new ones prefixed by >>):

fs/afs/write.c: In function 'afs_write_begin':
>> fs/afs/write.c:40:10: warning: variable 'index' set but not used [-Wunused-but-set-variable]
40 | pgoff_t index;
| ^~~~~


vim +/index +40 fs/afs/write.c

31143d5d515ece David Howells 2007-05-09 26
31143d5d515ece David Howells 2007-05-09 27 /*
d5cb85d0ca8576 David Howells 2021-06-14 28 * Prepare to perform part of a write to a page. Note that len may extend
d5cb85d0ca8576 David Howells 2021-06-14 29 * beyond the end of the page.
31143d5d515ece David Howells 2007-05-09 30 */
15b4650e55e06d Nicholas Piggin 2008-10-15 31 int afs_write_begin(struct file *file, struct address_space *mapping,
15b4650e55e06d Nicholas Piggin 2008-10-15 32 loff_t pos, unsigned len, unsigned flags,
21db2cdc667f74 David Howells 2020-10-22 33 struct page **_page, void **fsdata)
31143d5d515ece David Howells 2007-05-09 34 {
496ad9aa8ef448 Al Viro 2013-01-23 35 struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
15b4650e55e06d Nicholas Piggin 2008-10-15 36 struct page *page;
4343d00872e1de David Howells 2017-11-02 37 unsigned long priv;
e87b03f5830ecd David Howells 2020-10-20 38 unsigned f, from;
e87b03f5830ecd David Howells 2020-10-20 39 unsigned t, to;
e87b03f5830ecd David Howells 2020-10-20 @40 pgoff_t index;
31143d5d515ece David Howells 2007-05-09 41 int ret;
31143d5d515ece David Howells 2007-05-09 42
e87b03f5830ecd David Howells 2020-10-20 43 _enter("{%llx:%llu},%llx,%x",
e87b03f5830ecd David Howells 2020-10-20 44 vnode->fid.vid, vnode->fid.vnode, pos, len);
31143d5d515ece David Howells 2007-05-09 45
3003bbd0697b65 David Howells 2020-02-06 46 /* Prefetch area to be written into the cache if we're caching this
3003bbd0697b65 David Howells 2020-02-06 47 * file. We need to do this before we get a lock on the page in case
3003bbd0697b65 David Howells 2020-02-06 48 * there's more than one writer competing for the same cache block.
3003bbd0697b65 David Howells 2020-02-06 49 */
3003bbd0697b65 David Howells 2020-02-06 50 ret = netfs_write_begin(file, mapping, pos, len, flags, &page, fsdata,
3003bbd0697b65 David Howells 2020-02-06 51 &afs_req_ops, NULL);
3003bbd0697b65 David Howells 2020-02-06 52 if (ret < 0)
31143d5d515ece David Howells 2007-05-09 53 return ret;
630f5dda8442ca David Howells 2020-02-06 54
e87b03f5830ecd David Howells 2020-10-20 55 index = page->index;
d5cb85d0ca8576 David Howells 2021-06-14 56 from = offset_in_thp(page, pos);
d5cb85d0ca8576 David Howells 2021-06-14 57 len = min_t(size_t, len, thp_size(page) - from);
e87b03f5830ecd David Howells 2020-10-20 58 to = from + len;
e87b03f5830ecd David Howells 2020-10-20 59
31143d5d515ece David Howells 2007-05-09 60 try_again:
4343d00872e1de David Howells 2017-11-02 61 /* See if this page is already partially written in a way that we can
4343d00872e1de David Howells 2017-11-02 62 * merge the new write with.
4343d00872e1de David Howells 2017-11-02 63 */
4343d00872e1de David Howells 2017-11-02 64 if (PagePrivate(page)) {
4343d00872e1de David Howells 2017-11-02 65 priv = page_private(page);
67d78a6f6e7b38 David Howells 2020-10-28 66 f = afs_page_dirty_from(page, priv);
67d78a6f6e7b38 David Howells 2020-10-28 67 t = afs_page_dirty_to(page, priv);
4343d00872e1de David Howells 2017-11-02 68 ASSERTCMP(f, <=, t);
4343d00872e1de David Howells 2017-11-02 69
5a039c32271b9a David Howells 2017-11-18 70 if (PageWriteback(page)) {
67d78a6f6e7b38 David Howells 2020-10-28 71 trace_afs_page_dirty(vnode, tracepoint_string("alrdy"), page);
5a039c32271b9a David Howells 2017-11-18 72 goto flush_conflicting_write;
5a039c32271b9a David Howells 2017-11-18 73 }
5a8132761609bd David Howells 2018-04-06 74 /* If the file is being filled locally, allow inter-write
5a8132761609bd David Howells 2018-04-06 75 * spaces to be merged into writes. If it's not, only write
5a8132761609bd David Howells 2018-04-06 76 * back what the user gives us.
5a8132761609bd David Howells 2018-04-06 77 */
5a8132761609bd David Howells 2018-04-06 78 if (!test_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags) &&
5a8132761609bd David Howells 2018-04-06 79 (to < f || from > t))
4343d00872e1de David Howells 2017-11-02 80 goto flush_conflicting_write;
31143d5d515ece David Howells 2007-05-09 81 }
31143d5d515ece David Howells 2007-05-09 82
21db2cdc667f74 David Howells 2020-10-22 83 *_page = page;
4343d00872e1de David Howells 2017-11-02 84 _leave(" = 0");
31143d5d515ece David Howells 2007-05-09 85 return 0;
31143d5d515ece David Howells 2007-05-09 86
4343d00872e1de David Howells 2017-11-02 87 /* The previous write and this write aren't adjacent or overlapping, so
4343d00872e1de David Howells 2017-11-02 88 * flush the page out.
4343d00872e1de David Howells 2017-11-02 89 */
4343d00872e1de David Howells 2017-11-02 90 flush_conflicting_write:
31143d5d515ece David Howells 2007-05-09 91 _debug("flush conflict");
4343d00872e1de David Howells 2017-11-02 92 ret = write_one_page(page);
21db2cdc667f74 David Howells 2020-10-22 93 if (ret < 0)
21db2cdc667f74 David Howells 2020-10-22 94 goto error;
31143d5d515ece David Howells 2007-05-09 95
4343d00872e1de David Howells 2017-11-02 96 ret = lock_page_killable(page);
21db2cdc667f74 David Howells 2020-10-22 97 if (ret < 0)
21db2cdc667f74 David Howells 2020-10-22 98 goto error;
21db2cdc667f74 David Howells 2020-10-22 99 goto try_again;
21db2cdc667f74 David Howells 2020-10-22 100
21db2cdc667f74 David Howells 2020-10-22 101 error:
21db2cdc667f74 David Howells 2020-10-22 102 put_page(page);
4343d00872e1de David Howells 2017-11-02 103 _leave(" = %d", ret);
4343d00872e1de David Howells 2017-11-02 104 return ret;
4343d00872e1de David Howells 2017-11-02 105 }
31143d5d515ece David Howells 2007-05-09 106

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