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[RFC PATCH 4/5] t1700-split-index: date back files to avoid racy situations

From
SZEDER Gábor <szeder.dev@gmail.com>
Date
Sep 6, 2018, 02:48 UTC
Message-ID
<20180906024810.8074-5-szeder.dev@gmail.com>
In-Reply-To
<20180906024810.8074-1-szeder.dev@gmail.com>

't1700-split-index.sh' checks that the index was split correctly under various circumstances and that all the different ways to turn the split index feature on and off work correctly. To do so, most of its tests use 'test-tool dump-split-index' to see which files have their cache entries in the split index. All these tests assume that all cache entries are written to the shared index (called "base" throughout these tests) when a new shared index is created. This is an implementation detail: most git commands (basically all except 'git update-index') don't care or know at all about split index or whether a cache entry is stored in the split or shared index.

As demonstrated in the previous patch, refreshing a split index is prone to a variant of the classic racy git issue. The next patch will fix this issue, but while doing so it will also slightly change this behaviour: only cache entries with mtime in the past will be written only to the newly created shared index, but racily clean cache entries will be written to the new split index (with smudged stat data).

While this upcoming change won't at all affect any git commands, it will violate the above mentioned assumption of 't1700's tests. Since these tests create or modify files and create or refresh the split index in rapid succession, there are plenty of racily clean cache entries to be dealt with, which will then be written to the new split indexes, and, ultimately, will cause several tests in 't1700' to fail.

Let's prepare 't1700-split-index.sh' for this upcoming change and modify its tests to avoid racily clean files by backdating the mtime of any file modifications (and since a lot of tests create or modify files, encapsulate it into a helper function).

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
---
 t/t1700-split-index.sh | 49 ++++++++++++++++++++++++------------------
 1 file changed, 28 insertions(+), 21 deletions(-)
diff --git a/t/t1700-split-index.sh b/t/t1700-split-index.sh
index be22398a85..e7beef1e09 100755
--- a/t/t1700-split-index.sh
+++ b/t/t1700-split-index.sh
@@ -8,6 +8,13 @@ test_description='split index mode tests'
 sane_unset GIT_TEST_SPLIT_INDEX
 sane_unset GIT_FSMONITOR_TEST
 
+# Create a file named as $1 with content read from stdin.
+# Set the file's mtime to a few seconds in the past to avoid racy situations.
+create_file () {
+	cat >"$1" &&
+	test-tool chmtime =-5 "$1"
+}
+
 test_expect_success 'enable split index' '
 	git config splitIndex.maxPercentChange 100 &&
 	git update-index --split-index &&
@@ -31,7 +38,7 @@ test_expect_success 'enable split index' '
 '
 
 test_expect_success 'add one file' '
-	: >one &&
+	create_file one &&
 	git update-index --add one &&
 	git ls-files --stage >ls-files.actual &&
 	cat >ls-files.expect <<-EOF &&
@@ -83,7 +90,7 @@ test_expect_success 'enable split index again, "one" now belongs to base index"'
 '
 
 test_expect_success 'modify original file, base index untouched' '
-	echo modified >one &&
+	echo modified |create_file one &&
 	git update-index one &&
 	git ls-files --stage >ls-files.actual &&
 	cat >ls-files.expect <<-EOF &&
@@ -102,7 +109,7 @@ test_expect_success 'modify original file, base index untouched' '
 '
 
 test_expect_success 'add another file, which stays index' '
-	: >two &&
+	create_file two &&
 	git update-index --add two &&
 	git ls-files --stage >ls-files.actual &&
 	cat >ls-files.expect <<-EOF &&
@@ -155,7 +162,7 @@ test_expect_success 'remove file in base index' '
 '
 
 test_expect_success 'add original file back' '
-	: >one &&
+	create_file one &&
 	git update-index --add one &&
 	git ls-files --stage >ls-files.actual &&
 	cat >ls-files.expect <<-EOF &&
@@ -174,7 +181,7 @@ test_expect_success 'add original file back' '
 '
 
 test_expect_success 'add new file' '
-	: >two &&
+	create_file two &&
 	git update-index --add two &&
 	git ls-files --stage >actual &&
 	cat >expect <<-EOF &&
@@ -218,7 +225,7 @@ test_expect_success 'rev-parse --shared-index-path' '
 
 test_expect_success 'set core.splitIndex config variable to true' '
 	git config core.splitIndex true &&
-	: >three &&
+	create_file three &&
 	git update-index --add three &&
 	git ls-files --stage >ls-files.actual &&
 	cat >ls-files.expect <<-EOF &&
@@ -253,9 +260,9 @@ test_expect_success 'set core.splitIndex config variable to false' '
 	test_cmp expect actual
 '
 
-test_expect_success 'set core.splitIndex config variable to true' '
+test_expect_success 'set core.splitIndex config variable back to true' '
 	git config core.splitIndex true &&
-	: >three &&
+	create_file three &&
 	git update-index --add three &&
 	BASE=$(test-tool dump-split-index .git/index | grep "^base") &&
 	test-tool dump-split-index .git/index | sed "/^own/d" >actual &&
@@ -265,7 +272,7 @@ test_expect_success 'set core.splitIndex config variable to true' '
 	deletions:
 	EOF
 	test_cmp expect actual &&
-	: >four &&
+	create_file four &&
 	git update-index --add four &&
 	test-tool dump-split-index .git/index | sed "/^own/d" >actual &&
 	cat >expect <<-EOF &&
@@ -279,7 +286,7 @@ test_expect_success 'set core.splitIndex config variable to true' '
 
 test_expect_success 'check behavior with splitIndex.maxPercentChange unset' '
 	git config --unset splitIndex.maxPercentChange &&
-	: >five &&
+	create_file five &&
 	git update-index --add five &&
 	BASE=$(test-tool dump-split-index .git/index | grep "^base") &&
 	test-tool dump-split-index .git/index | sed "/^own/d" >actual &&
@@ -289,7 +296,7 @@ test_expect_success 'check behavior with splitIndex.maxPercentChange unset' '
 	deletions:
 	EOF
 	test_cmp expect actual &&
-	: >six &&
+	create_file six &&
 	git update-index --add six &&
 	test-tool dump-split-index .git/index | sed "/^own/d" >actual &&
 	cat >expect <<-EOF &&
@@ -303,7 +310,7 @@ test_expect_success 'check behavior with splitIndex.maxPercentChange unset' '
 
 test_expect_success 'check splitIndex.maxPercentChange set to 0' '
 	git config splitIndex.maxPercentChange 0 &&
-	: >seven &&
+	create_file seven &&
 	git update-index --add seven &&
 	BASE=$(test-tool dump-split-index .git/index | grep "^base") &&
 	test-tool dump-split-index .git/index | sed "/^own/d" >actual &&
@@ -313,7 +320,7 @@ test_expect_success 'check splitIndex.maxPercentChange set to 0' '
 	deletions:
 	EOF
 	test_cmp expect actual &&
-	: >eight &&
+	create_file eight &&
 	git update-index --add eight &&
 	BASE=$(test-tool dump-split-index .git/index | grep "^base") &&
 	test-tool dump-split-index .git/index | sed "/^own/d" >actual &&
@@ -326,17 +333,17 @@ test_expect_success 'check splitIndex.maxPercentChange set to 0' '
 '
 
 test_expect_success 'shared index files expire after 2 weeks by default' '
-	: >ten &&
+	create_file ten &&
 	git update-index --add ten &&
 	test $(ls .git/sharedindex.* | wc -l) -gt 2 &&
 	just_under_2_weeks_ago=$((5-14*86400)) &&
 	test-tool chmtime =$just_under_2_weeks_ago .git/sharedindex.* &&
-	: >eleven &&
+	create_file eleven &&
 	git update-index --add eleven &&
 	test $(ls .git/sharedindex.* | wc -l) -gt 2 &&
 	just_over_2_weeks_ago=$((-1-14*86400)) &&
 	test-tool chmtime =$just_over_2_weeks_ago .git/sharedindex.* &&
-	: >twelve &&
+	create_file twelve &&
 	git update-index --add twelve &&
 	test $(ls .git/sharedindex.* | wc -l) -le 2
 '
@@ -344,12 +351,12 @@ test_expect_success 'shared index files expire after 2 weeks by default' '
 test_expect_success 'check splitIndex.sharedIndexExpire set to 16 days' '
 	git config splitIndex.sharedIndexExpire "16.days.ago" &&
 	test-tool chmtime =$just_over_2_weeks_ago .git/sharedindex.* &&
-	: >thirteen &&
+	create_file thirteen &&
 	git update-index --add thirteen &&
 	test $(ls .git/sharedindex.* | wc -l) -gt 2 &&
 	just_over_16_days_ago=$((-1-16*86400)) &&
 	test-tool chmtime =$just_over_16_days_ago .git/sharedindex.* &&
-	: >fourteen &&
+	create_file fourteen &&
 	git update-index --add fourteen &&
 	test $(ls .git/sharedindex.* | wc -l) -le 2
 '
@@ -358,13 +365,13 @@ test_expect_success 'check splitIndex.sharedIndexExpire set to "never" and "now"
 	git config splitIndex.sharedIndexExpire never &&
 	just_10_years_ago=$((-365*10*86400)) &&
 	test-tool chmtime =$just_10_years_ago .git/sharedindex.* &&
-	: >fifteen &&
+	create_file fifteen &&
 	git update-index --add fifteen &&
 	test $(ls .git/sharedindex.* | wc -l) -gt 2 &&
 	git config splitIndex.sharedIndexExpire now &&
 	just_1_second_ago=-1 &&
 	test-tool chmtime =$just_1_second_ago .git/sharedindex.* &&
-	: >sixteen &&
+	create_file sixteen &&
 	git update-index --add sixteen &&
 	test $(ls .git/sharedindex.* | wc -l) -le 2
 '
@@ -379,7 +386,7 @@ do
 		# Create one new shared index file
 		git config core.sharedrepository "$mode" &&
 		git config core.splitIndex true &&
-		: >one &&
+		create_file one &&
 		git update-index --add one &&
 		echo "$modebits" >expect &&
 		test_modebits .git/index >actual &&

-- 
2.19.0.rc0.188.g56c5ee2db1
Previous: SZEDER GáborNext: Ævar Arnfjörð Bjarmason
Message 8 of 20 in “Fix the racy split index problem”
  1. 0/5 Fix the racy split index problemSZEDER Gábor, Sep 6, 2018
  2. 1/5 t1700-split-index: drop unnecessary 'grep'SZEDER Gábor, Sep 6, 2018
  3. Junio C HamanoSep 6, 2018
  4. Duy NguyenSep 8, 2018
  5. 2/5 t0090: disable GIT_TEST_SPLIT_INDEX for the test checking split indexSZEDER Gábor, Sep 6, 2018
  6. Ævar Arnfjörð BjarmasonSep 6, 2018
  7. 3/5 split index: add a test to demonstrate the racy split index problemSZEDER Gábor, Sep 6, 2018
  8. 4/5 t1700-split-index: date back files to avoid racy situationsSZEDER Gábor, Sep 6, 2018
  9. Ævar Arnfjörð BjarmasonSep 6, 2018
  10. SZEDER GáborSep 6, 2018
  11. Ævar Arnfjörð BjarmasonSep 6, 2018
  12. 5/5 split-index: smudge and add racily clean cache entries to split indexSZEDER Gábor, Sep 6, 2018
  13. Ævar Arnfjörð BjarmasonSep 6, 2018
  14. Ævar Arnfjörð BjarmasonSep 6, 2018
  15. SZEDER GáborSep 6, 2018
  16. Ævar Arnfjörð BjarmasonSep 6, 2018
  17. Ævar Arnfjörð BjarmasonSep 6, 2018
  18. SZEDER GáborSep 7, 2018
  19. Paul-Sebastian UngureanuSep 10, 2018
  20. Duy NguyenSep 8, 2018

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