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read-cache: don't write index twice if we can't write shared index 

In a0a967568e ("update-index --split-index: do not split if $GIT_DIR is
read only", 2014-06-13), we tried to make sure we can still write an
index, even if the shared index can not be written.

We did so by just calling 'do_write_locked_index()' just before
'write_shared_index()'.  'do_write_locked_index()' always at least
closes the tempfile nowadays, and used to close or commit the lockfile
if COMMIT_LOCK or CLOSE_LOCK were given at the time this feature was
introduced.  COMMIT_LOCK or CLOSE_LOCK is passed in by most callers of
'write_locked_index()'.

After calling 'write_shared_index()', we call 'write_split_index()',
which calls 'do_write_locked_index()' again, which then tries to use the
closed lockfile again, but in fact fails to do so as it's already
closed. This eventually leads to a segfault.

Make sure to write the main index only once.

[nd: most of the commit message and investigation done by Thomas, I only
tweaked the solution a bit]

Helped-by: Thomas Gummerer <t.gummerer@gmail.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Nguyễn Thái Ngọc Duy 2018-01-24 16:38:29 +07:00 committed by Junio C Hamano
parent 59f9d2dd60
commit ef5b3a6c5e
2 changed files with 22 additions and 2 deletions
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5
read-cache.c
View File

@ -2561,8 +2561,9 @@ int write_locked_index(struct index_state *istate, struct lock_file *lock,
if (!temp) {
hashclr(si->base_sha1);
ret = do_write_locked_index(istate, lock, flags);
} else
ret = write_shared_index(istate, &temp);
goto out;
}
ret = write_shared_index(istate, &temp);
saved_errno = errno;
if (is_tempfile_active(temp))

19
t/t1700-split-index.sh
View File

@ -401,4 +401,23 @@ done <<\EOF
0642 -rw-r---w-
EOF
test_expect_success POSIXPERM,SANITY 'graceful handling when splitting index is not allowed' '
test_create_repo ro &&
(
cd ro &&
test_commit initial &&
git update-index --split-index &&
test -f .git/sharedindex.*
) &&
cp ro/.git/index new-index &&
test_when_finished "chmod u+w ro/.git" &&
chmod u-w ro/.git &&
GIT_INDEX_FILE="$(pwd)/new-index" git -C ro update-index --split-index &&
chmod u+w ro/.git &&
rm ro/.git/sharedindex.* &&
GIT_INDEX_FILE=new-index git ls-files >actual &&
echo initial.t >expected &&
test_cmp expected actual
'
test_done