git@vger.kernel.org list mirror (unofficial, one of many)
 help / color / mirror / code / Atom feed
From: Junio C Hamano <gitster@pobox.com>
To: Kevin Willford <Kevin.Willford@microsoft.com>
Cc: Utsav Shah via GitGitGadget <gitgitgadget@gmail.com>,
	William Baker <William.Baker@microsoft.com>,
	"git\@vger.kernel.org" <git@vger.kernel.org>,
	Utsav Shah <ukshah2@illinois.edu>
Subject: Re: [PATCH 0/1] fsmonitor: skip sanity check if the index is split
Date: Wed, 13 Nov 2019 10:30:05 +0900	[thread overview]
Message-ID: <xmqqzhh0d0ma.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <BN6PR21MB07869E8D1DCAF189C4E472A891740@BN6PR21MB0786.namprd21.prod.outlook.com> (Kevin Willford's message of "Mon, 11 Nov 2019 16:55:11 +0000")

Kevin Willford <Kevin.Willford@microsoft.com> writes:

> I agree.  The only 2 places that excluding the split-index make sense are in
> read_fsmonitor_extension and write_fsmonitor_extension because the
> index_state that is being passing into those methods could be the delta index
> in which case the number of entries for the fsmonitor bitmap would almost
> always be more and cause the BUG to be hit which it should not be.

Thanks.  Here is what I came up with to tie the loose ends of this
thread.

-- >8 --
From: Junio C Hamano <gitster@pobox.com>
Subject: [PATCH] fsmonitor: do not compare bitmap size with size of split index

3444ec2e ("fsmonitor: don't fill bitmap with entries to be removed",
2019-10-11) added a handful of sanity checks that make sure that a
bit position in fsmonitor bitmap does not go beyond the end of the
index.  As each bit in the bitmap corresponds to a path in the
index, this is the right check most of the time.

Except for the case when we are in the split-index mode and looking
at a delta index that is to be overlayed on the base index but
before the base index has actually been merged in, namely in read_
and write_fsmonitor_extension().  In these codepaths, the entries in
the split/delta index is typically a small subset of the entire set
of paths (otherwise why would we be using split-index?), so the
bitmap used by the fsmonitor is almost always larger than the number
of entries in the partial index, and the incorrect comparison would
trigger the BUG().

Reported-by: Utsav Shah <ukshah2@illinois.edu>
Helped-by: Kevin Willford <Kevin.Willford@microsoft.com>
Helped-by: William Baker <William.Baker@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 fsmonitor.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fsmonitor.c b/fsmonitor.c
index 1f4aa1b150..0477500b39 100644
--- a/fsmonitor.c
+++ b/fsmonitor.c
@@ -55,7 +55,8 @@ int read_fsmonitor_extension(struct index_state *istate, const void *data,
 	}
 	istate->fsmonitor_dirty = fsmonitor_dirty;
 
-	if (istate->fsmonitor_dirty->bit_size > istate->cache_nr)
+	if (!istate->split_index &&
+	    istate->fsmonitor_dirty->bit_size > istate->cache_nr)
 		BUG("fsmonitor_dirty has more entries than the index (%"PRIuMAX" > %u)",
 		    (uintmax_t)istate->fsmonitor_dirty->bit_size, istate->cache_nr);
 
@@ -83,7 +84,8 @@ void write_fsmonitor_extension(struct strbuf *sb, struct index_state *istate)
 	uint32_t ewah_size = 0;
 	int fixup = 0;
 
-	if (istate->fsmonitor_dirty->bit_size > istate->cache_nr)
+	if (!istate->split_index &&
+	    istate->fsmonitor_dirty->bit_size > istate->cache_nr)
 		BUG("fsmonitor_dirty has more entries than the index (%"PRIuMAX" > %u)",
 		    (uintmax_t)istate->fsmonitor_dirty->bit_size, istate->cache_nr);
 
-- 
2.24.0-346-gee0de6d492


  parent reply	other threads:[~2019-11-13  1:30 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-08  7:09 Utsav Shah via GitGitGadget
2019-11-08  7:09 ` [PATCH 1/1] " Utsav Shah via GitGitGadget
2019-11-12 11:18   ` SZEDER Gábor
2019-11-12 21:08     ` Utsav Shah
2019-11-11  1:43 ` [PATCH 0/1] " Junio C Hamano
2019-11-11  2:01   ` Junio C Hamano
2019-11-11 16:55     ` Kevin Willford
2019-11-11 17:25       ` Utsav Shah
2019-11-11 18:21         ` Kevin Willford
2019-11-11 17:30       ` William Baker
2019-11-13  1:30       ` Junio C Hamano [this message]
2019-11-14  2:55         ` Utsav Shah
2019-11-14 16:41         ` William Baker
2019-11-15  5:04           ` Junio C Hamano

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: http://vger.kernel.org/majordomo-info.html

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=xmqqzhh0d0ma.fsf@gitster-ct.c.googlers.com \
    --to=gitster@pobox.com \
    --cc=Kevin.Willford@microsoft.com \
    --cc=William.Baker@microsoft.com \
    --cc=git@vger.kernel.org \
    --cc=gitgitgadget@gmail.com \
    --cc=ukshah2@illinois.edu \
    --subject='Re: [PATCH 0/1] fsmonitor: skip sanity check if the index is split' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Code repositories for project(s) associated with this inbox:

	https://80x24.org/mirrors/git.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).