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authorJunio C Hamano <gitster@pobox.com>2018-10-26 05:22:10 (GMT)
committerJunio C Hamano <gitster@pobox.com>2018-10-26 05:22:10 (GMT)
commit7a43ab6fb25924ca018073ef7ef46e16b3156bd0 (patch)
tree08b311fbea07553319c3cd651908dce9aee98505
parent3c4a8214a07d3903c1563ee0bd98a886874146b6 (diff)
parent4c490f3d321da415b8d3bec4a04565906657b9c9 (diff)
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Merge branch 'sg/split-index-racefix'
The codepath to support the experimental split-index mode had remaining "racily clean" issues fixed. * sg/split-index-racefix: split-index: BUG() when cache entry refers to non-existing shared entry split-index: smudge and add racily clean cache entries to split index split-index: don't compare cached data of entries already marked for split index split-index: count the number of deleted entries t1700-split-index: date back files to avoid racy situations split-index: add tests to demonstrate the racy split index problem t1700-split-index: document why FSMONITOR is disabled in this test script
-rw-r--r--cache.h2
-rw-r--r--read-cache.c2
-rw-r--r--split-index.c135
-rwxr-xr-xt/t1700-split-index.sh49
-rwxr-xr-xt/t1701-racy-split-index.sh214
5 files changed, 360 insertions, 42 deletions
diff --git a/cache.h b/cache.h
index 59c8a93..f7fabdd 100644
--- a/cache.h
+++ b/cache.h
@@ -783,6 +783,8 @@ extern void *read_blob_data_from_index(const struct index_state *, const char *,
#define CE_MATCH_REFRESH 0x10
/* don't refresh_fsmonitor state or do stat comparison even if CE_FSMONITOR_VALID is true */
#define CE_MATCH_IGNORE_FSMONITOR 0X20
+extern int is_racy_timestamp(const struct index_state *istate,
+ const struct cache_entry *ce);
extern int ie_match_stat(struct index_state *, const struct cache_entry *, struct stat *, unsigned int);
extern int ie_modified(struct index_state *, const struct cache_entry *, struct stat *, unsigned int);
diff --git a/read-cache.c b/read-cache.c
index 1df5c16..d579582 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -345,7 +345,7 @@ static int is_racy_stat(const struct index_state *istate,
);
}
-static int is_racy_timestamp(const struct index_state *istate,
+int is_racy_timestamp(const struct index_state *istate,
const struct cache_entry *ce)
{
return (!S_ISGITLINK(ce->ce_mode) &&
diff --git a/split-index.c b/split-index.c
index 84f067e..5820412 100644
--- a/split-index.c
+++ b/split-index.c
@@ -111,7 +111,7 @@ static void mark_entry_for_delete(size_t pos, void *data)
die("position for delete %d exceeds base index size %d",
(int)pos, istate->cache_nr);
istate->cache[pos]->ce_flags |= CE_REMOVE;
- istate->split_index->nr_deletions = 1;
+ istate->split_index->nr_deletions++;
}
static void replace_entry(size_t pos, void *data)
@@ -188,6 +188,30 @@ void merge_base_index(struct index_state *istate)
si->saved_cache_nr = 0;
}
+/*
+ * Compare most of the fields in two cache entries, i.e. all except the
+ * hashmap_entry and the name.
+ */
+static int compare_ce_content(struct cache_entry *a, struct cache_entry *b)
+{
+ const unsigned int ondisk_flags = CE_STAGEMASK | CE_VALID |
+ CE_EXTENDED_FLAGS;
+ unsigned int ce_flags = a->ce_flags;
+ unsigned int base_flags = b->ce_flags;
+ int ret;
+
+ /* only on-disk flags matter */
+ a->ce_flags &= ondisk_flags;
+ b->ce_flags &= ondisk_flags;
+ ret = memcmp(&a->ce_stat_data, &b->ce_stat_data,
+ offsetof(struct cache_entry, name) -
+ offsetof(struct cache_entry, ce_stat_data));
+ a->ce_flags = ce_flags;
+ b->ce_flags = base_flags;
+
+ return ret;
+}
+
void prepare_to_write_split_index(struct index_state *istate)
{
struct split_index *si = init_split_index(istate);
@@ -207,38 +231,109 @@ void prepare_to_write_split_index(struct index_state *istate)
*/
for (i = 0; i < istate->cache_nr; i++) {
struct cache_entry *base;
- /* namelen is checked separately */
- const unsigned int ondisk_flags =
- CE_STAGEMASK | CE_VALID | CE_EXTENDED_FLAGS;
- unsigned int ce_flags, base_flags, ret;
ce = istate->cache[i];
- if (!ce->index)
+ if (!ce->index) {
+ /*
+ * During simple update index operations this
+ * is a cache entry that is not present in
+ * the shared index. It will be added to the
+ * split index.
+ *
+ * However, it might also represent a file
+ * that already has a cache entry in the
+ * shared index, but a new index has just
+ * been constructed by unpack_trees(), and
+ * this entry now refers to different content
+ * than what was recorded in the original
+ * index, e.g. during 'read-tree -m HEAD^' or
+ * 'checkout HEAD^'. In this case the
+ * original entry in the shared index will be
+ * marked as deleted, and this entry will be
+ * added to the split index.
+ */
continue;
+ }
if (ce->index > si->base->cache_nr) {
- ce->index = 0;
- continue;
+ BUG("ce refers to a shared ce at %d, which is beyond the shared index size %d",
+ ce->index, si->base->cache_nr);
}
ce->ce_flags |= CE_MATCHED; /* or "shared" */
base = si->base->cache[ce->index - 1];
- if (ce == base)
+ if (ce == base) {
+ /* The entry is present in the shared index. */
+ if (ce->ce_flags & CE_UPDATE_IN_BASE) {
+ /*
+ * Already marked for inclusion in
+ * the split index, either because
+ * the corresponding file was
+ * modified and the cached stat data
+ * was refreshed, or because there
+ * is already a replacement entry in
+ * the split index.
+ * Nothing more to do here.
+ */
+ } else if (!ce_uptodate(ce) &&
+ is_racy_timestamp(istate, ce)) {
+ /*
+ * A racily clean cache entry stored
+ * only in the shared index: it must
+ * be added to the split index, so
+ * the subsequent do_write_index()
+ * can smudge its stat data.
+ */
+ ce->ce_flags |= CE_UPDATE_IN_BASE;
+ } else {
+ /*
+ * The entry is only present in the
+ * shared index and it was not
+ * refreshed.
+ * Just leave it there.
+ */
+ }
continue;
+ }
if (ce->ce_namelen != base->ce_namelen ||
strcmp(ce->name, base->name)) {
ce->index = 0;
continue;
}
- ce_flags = ce->ce_flags;
- base_flags = base->ce_flags;
- /* only on-disk flags matter */
- ce->ce_flags &= ondisk_flags;
- base->ce_flags &= ondisk_flags;
- ret = memcmp(&ce->ce_stat_data, &base->ce_stat_data,
- offsetof(struct cache_entry, name) -
- offsetof(struct cache_entry, ce_stat_data));
- ce->ce_flags = ce_flags;
- base->ce_flags = base_flags;
- if (ret)
+ /*
+ * This is the copy of a cache entry that is present
+ * in the shared index, created by unpack_trees()
+ * while it constructed a new index.
+ */
+ if (ce->ce_flags & CE_UPDATE_IN_BASE) {
+ /*
+ * Already marked for inclusion in the split
+ * index, either because the corresponding
+ * file was modified and the cached stat data
+ * was refreshed, or because the original
+ * entry already had a replacement entry in
+ * the split index.
+ * Nothing to do.
+ */
+ } else if (!ce_uptodate(ce) &&
+ is_racy_timestamp(istate, ce)) {
+ /*
+ * A copy of a racily clean cache entry from
+ * the shared index. It must be added to
+ * the split index, so the subsequent
+ * do_write_index() can smudge its stat data.
+ */
ce->ce_flags |= CE_UPDATE_IN_BASE;
+ } else {
+ /*
+ * Thoroughly compare the cached data to see
+ * whether it should be marked for inclusion
+ * in the split index.
+ *
+ * This comparison might be unnecessary, as
+ * code paths modifying the cached data do
+ * set CE_UPDATE_IN_BASE as well.
+ */
+ if (compare_ce_content(ce, base))
+ ce->ce_flags |= CE_UPDATE_IN_BASE;
+ }
discard_cache_entry(base);
si->base->cache[ce->index - 1] = ce;
}
diff --git a/t/t1700-split-index.sh b/t/t1700-split-index.sh
index 3e618ca..2ac47aa 100755
--- a/t/t1700-split-index.sh
+++ b/t/t1700-split-index.sh
@@ -13,6 +13,13 @@ sane_unset GIT_TEST_SPLIT_INDEX
sane_unset GIT_TEST_FSMONITOR
sane_unset GIT_TEST_INDEX_THREADS
+# 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_non_racy_file () {
+ cat >"$1" &&
+ test-tool chmtime =-5 "$1"
+}
+
test_expect_success 'enable split index' '
git config splitIndex.maxPercentChange 100 &&
git update-index --split-index &&
@@ -36,7 +43,7 @@ test_expect_success 'enable split index' '
'
test_expect_success 'add one file' '
- : >one &&
+ create_non_racy_file one &&
git update-index --add one &&
git ls-files --stage >ls-files.actual &&
cat >ls-files.expect <<-EOF &&
@@ -88,7 +95,7 @@ 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_non_racy_file one &&
git update-index one &&
git ls-files --stage >ls-files.actual &&
cat >ls-files.expect <<-EOF &&
@@ -107,7 +114,7 @@ test_expect_success 'modify original file, base index untouched' '
'
test_expect_success 'add another file, which stays index' '
- : >two &&
+ create_non_racy_file two &&
git update-index --add two &&
git ls-files --stage >ls-files.actual &&
cat >ls-files.expect <<-EOF &&
@@ -160,7 +167,7 @@ test_expect_success 'remove file in base index' '
'
test_expect_success 'add original file back' '
- : >one &&
+ create_non_racy_file one &&
git update-index --add one &&
git ls-files --stage >ls-files.actual &&
cat >ls-files.expect <<-EOF &&
@@ -179,7 +186,7 @@ test_expect_success 'add original file back' '
'
test_expect_success 'add new file' '
- : >two &&
+ create_non_racy_file two &&
git update-index --add two &&
git ls-files --stage >actual &&
cat >expect <<-EOF &&
@@ -223,7 +230,7 @@ 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_non_racy_file three &&
git update-index --add three &&
git ls-files --stage >ls-files.actual &&
cat >ls-files.expect <<-EOF &&
@@ -258,9 +265,9 @@ 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_non_racy_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 &&
@@ -270,7 +277,7 @@ test_expect_success 'set core.splitIndex config variable to true' '
deletions:
EOF
test_cmp expect actual &&
- : >four &&
+ create_non_racy_file four &&
git update-index --add four &&
test-tool dump-split-index .git/index | sed "/^own/d" >actual &&
cat >expect <<-EOF &&
@@ -284,7 +291,7 @@ 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_non_racy_file five &&
git update-index --add five &&
BASE=$(test-tool dump-split-index .git/index | grep "^base") &&
test-tool dump-split-index .git/index | sed "/^own/d" >actual &&
@@ -294,7 +301,7 @@ test_expect_success 'check behavior with splitIndex.maxPercentChange unset' '
deletions:
EOF
test_cmp expect actual &&
- : >six &&
+ create_non_racy_file six &&
git update-index --add six &&
test-tool dump-split-index .git/index | sed "/^own/d" >actual &&
cat >expect <<-EOF &&
@@ -308,7 +315,7 @@ test_expect_success 'check behavior with splitIndex.maxPercentChange unset' '
test_expect_success 'check splitIndex.maxPercentChange set to 0' '
git config splitIndex.maxPercentChange 0 &&
- : >seven &&
+ create_non_racy_file seven &&
git update-index --add seven &&
BASE=$(test-tool dump-split-index .git/index | grep "^base") &&
test-tool dump-split-index .git/index | sed "/^own/d" >actual &&
@@ -318,7 +325,7 @@ test_expect_success 'check splitIndex.maxPercentChange set to 0' '
deletions:
EOF
test_cmp expect actual &&
- : >eight &&
+ create_non_racy_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 &&
@@ -331,17 +338,17 @@ test_expect_success 'check splitIndex.maxPercentChange set to 0' '
'
test_expect_success 'shared index files expire after 2 weeks by default' '
- : >ten &&
+ create_non_racy_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_non_racy_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_non_racy_file twelve &&
git update-index --add twelve &&
test $(ls .git/sharedindex.* | wc -l) -le 2
'
@@ -349,12 +356,12 @@ test_expect_success 'shared index files expire after 2 weeks by default' '
test_expect_success 'check splitIndex.sharedIndexExpire set to 16 days' '
git config splitIndex.sharedIndexExpire "16.days.ago" &&
test-tool chmtime =$just_over_2_weeks_ago .git/sharedindex.* &&
- : >thirteen &&
+ create_non_racy_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_non_racy_file fourteen &&
git update-index --add fourteen &&
test $(ls .git/sharedindex.* | wc -l) -le 2
'
@@ -363,13 +370,13 @@ test_expect_success 'check splitIndex.sharedIndexExpire set to "never" and "now"
git config splitIndex.sharedIndexExpire never &&
just_10_years_ago=$((-365*10*86400)) &&
test-tool chmtime =$just_10_years_ago .git/sharedindex.* &&
- : >fifteen &&
+ create_non_racy_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_non_racy_file sixteen &&
git update-index --add sixteen &&
test $(ls .git/sharedindex.* | wc -l) -le 2
'
@@ -384,7 +391,7 @@ do
# Create one new shared index file
git config core.sharedrepository "$mode" &&
git config core.splitIndex true &&
- : >one &&
+ create_non_racy_file one &&
git update-index --add one &&
echo "$modebits" >expect &&
test_modebits .git/index >actual &&
diff --git a/t/t1701-racy-split-index.sh b/t/t1701-racy-split-index.sh
new file mode 100755
index 0000000..5dc221e
--- /dev/null
+++ b/t/t1701-racy-split-index.sh
@@ -0,0 +1,214 @@
+#!/bin/sh
+
+# This test can give false success if your machine is sufficiently
+# slow or all trials happened to happen on second boundaries.
+
+test_description='racy split index'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+ # Only split the index when the test explicitly says so.
+ sane_unset GIT_TEST_SPLIT_INDEX &&
+ git config splitIndex.maxPercentChange 100 &&
+
+ echo "cached content" >racy-file &&
+ git add racy-file &&
+ git commit -m initial &&
+
+ echo something >other-file &&
+ # No raciness with this file.
+ test-tool chmtime =-20 other-file &&
+
+ echo "+cached content" >expect
+'
+
+check_cached_diff () {
+ git diff-index --patch --cached $EMPTY_TREE racy-file >diff &&
+ tail -1 diff >actual &&
+ test_cmp expect actual
+}
+
+trials="0 1 2 3 4"
+for trial in $trials
+do
+ test_expect_success "split the index while adding a racily clean file #$trial" '
+ rm -f .git/index .git/sharedindex.* &&
+
+ # The next three commands must be run within the same
+ # second (so both writes to racy-file result in the same
+ # mtime) to create the interesting racy situation.
+ echo "cached content" >racy-file &&
+
+ # Update and split the index. The cache entry of
+ # racy-file will be stored only in the shared index.
+ git update-index --split-index --add racy-file &&
+
+ # File size must stay the same.
+ echo "dirty worktree" >racy-file &&
+
+ # Subsequent git commands should notice that racy-file
+ # and the split index have the same mtime, and check
+ # the content of the file to see if it is actually
+ # clean.
+ check_cached_diff
+ '
+done
+
+for trial in $trials
+do
+ test_expect_success "add a racily clean file to an already split index #$trial" '
+ rm -f .git/index .git/sharedindex.* &&
+
+ git update-index --split-index &&
+
+ # The next three commands must be run within the same
+ # second.
+ echo "cached content" >racy-file &&
+
+ # Update the split index. The cache entry of racy-file
+ # will be stored only in the split index.
+ git update-index --add racy-file &&
+
+ # File size must stay the same.
+ echo "dirty worktree" >racy-file &&
+
+ # Subsequent git commands should notice that racy-file
+ # and the split index have the same mtime, and check
+ # the content of the file to see if it is actually
+ # clean.
+ check_cached_diff
+ '
+done
+
+for trial in $trials
+do
+ test_expect_success "split the index when the index contains a racily clean cache entry #$trial" '
+ rm -f .git/index .git/sharedindex.* &&
+
+ # The next three commands must be run within the same
+ # second.
+ echo "cached content" >racy-file &&
+
+ git update-index --add racy-file &&
+
+ # File size must stay the same.
+ echo "dirty worktree" >racy-file &&
+
+ # Now wait a bit to ensure that the split index written
+ # below will get a more recent mtime than racy-file.
+ sleep 1 &&
+
+ # Update and split the index when the index contains
+ # the racily clean cache entry of racy-file.
+ # A corresponding replacement cache entry with smudged
+ # stat data should be added to the new split index.
+ git update-index --split-index --add other-file &&
+
+ # Subsequent git commands should notice the smudged
+ # stat data in the replacement cache entry and that it
+ # doesnt match with the file the worktree.
+ check_cached_diff
+ '
+done
+
+for trial in $trials
+do
+ test_expect_success "update the split index when it contains a new racily clean cache entry #$trial" '
+ rm -f .git/index .git/sharedindex.* &&
+
+ git update-index --split-index &&
+
+ # The next three commands must be run within the same
+ # second.
+ echo "cached content" >racy-file &&
+
+ # Update the split index. The cache entry of racy-file
+ # will be stored only in the split index.
+ git update-index --add racy-file &&
+
+ # File size must stay the same.
+ echo "dirty worktree" >racy-file &&
+
+ # Now wait a bit to ensure that the split index written
+ # below will get a more recent mtime than racy-file.
+ sleep 1 &&
+
+ # Update the split index when the racily clean cache
+ # entry of racy-file is only stored in the split index.
+ # An updated cache entry with smudged stat data should
+ # be added to the new split index.
+ git update-index --add other-file &&
+
+ # Subsequent git commands should notice the smudged
+ # stat data.
+ check_cached_diff
+ '
+done
+
+for trial in $trials
+do
+ test_expect_success "update the split index when a racily clean cache entry is stored only in the shared index #$trial" '
+ rm -f .git/index .git/sharedindex.* &&
+
+ # The next three commands must be run within the same
+ # second.
+ echo "cached content" >racy-file &&
+
+ # Update and split the index. The cache entry of
+ # racy-file will be stored only in the shared index.
+ git update-index --split-index --add racy-file &&
+
+ # File size must stay the same.
+ echo "dirty worktree" >racy-file &&
+
+ # Now wait a bit to ensure that the split index written
+ # below will get a more recent mtime than racy-file.
+ sleep 1 &&
+
+ # Update the split index when the racily clean cache
+ # entry of racy-file is only stored in the shared index.
+ # A corresponding replacement cache entry with smudged
+ # stat data should be added to the new split index.
+ git update-index --add other-file &&
+
+ # Subsequent git commands should notice the smudged
+ # stat data.
+ check_cached_diff
+ '
+done
+
+for trial in $trials
+do
+ test_expect_success "update the split index after unpack trees() copied a racily clean cache entry from the shared index #$trial" '
+ rm -f .git/index .git/sharedindex.* &&
+
+ # The next three commands must be run within the same
+ # second.
+ echo "cached content" >racy-file &&
+
+ # Update and split the index. The cache entry of
+ # racy-file will be stored only in the shared index.
+ git update-index --split-index --add racy-file &&
+
+ # File size must stay the same.
+ echo "dirty worktree" >racy-file &&
+
+ # Now wait a bit to ensure that the split index written
+ # below will get a more recent mtime than racy-file.
+ sleep 1 &&
+
+ # Update the split index after unpack_trees() copied the
+ # racily clean cache entry of racy-file from the shared
+ # index. A corresponding replacement cache entry
+ # with smudged stat data should be added to the new
+ # split index.
+ git read-tree -m HEAD &&
+
+ # Subsequent git commands should notice the smudged
+ # stat data.
+ check_cached_diff
+ '
+done
+
+test_done