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
next prev 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 [PATCH 0/1] fsmonitor: skip sanity check if the index is split 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
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