| Message ID | 20190130231359.23978-1-max@max630.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [RFC] pack-refs: fail on falsely sorted packed-refs | expand |
On Wed, Jan 30, 2019 at 6:21 PM Max Kirillov <max@max630.net> wrote: > If packed-refs is marked as sorted but not really sorted it causes > very hard to comprehend misbehavior of reference resolving - a reference > is reported as not found. > > As the scope of the issue is not clear, make it visible by failing > pack-refs command - the one which would not suffer performance penalty > to verify the sortedness - when it encounters not really sorted existing > data. > > Signed-off-by: Max Kirillov <max@max630.net> > --- > diff --git a/refs/packed-backend.c b/refs/packed-backend.c > @@ -1088,6 +1088,7 @@ static int write_with_updates(struct packed_ref_store *refs, > + struct strbuf prev_ref = STRBUF_INIT; > @@ -1137,6 +1138,20 @@ static int write_with_updates(struct packed_ref_store *refs, > + if (iter) > + { > + if (prev_ref.len && strcmp(prev_ref.buf, iter->refname) > 0) > + { > + strbuf_addf(err, "broken sorting in packed-refs: '%s' > '%s'", > + prev_ref.buf, > + iter->refname); strbuf_release(&prev_ref) either here or after the "error" label. > + goto error; > + } > + > + strbuf_init(&prev_ref, 0); > + strbuf_addstr(&prev_ref, iter->refname); > + } > diff --git a/t/t3212-pack-refs-broken-sorting.sh b/t/t3212-pack-refs-broken-sorting.sh > @@ -0,0 +1,26 @@ > +test_expect_success 'setup' ' > + git commit --allow-empty -m commit && > + for num in $(test_seq 10) > + do > + git branch b$(printf "%02d" $num) || break This should probably be "|| return 1" rather than "|| break" in order to fail the test immediately. > + done && > + git pack-refs --all && > + head_object=$(git rev-parse HEAD) && > + printf "$head_object refs/heads/b00\\n" >>.git/packed-refs && > + git branch b11 > +' > + > +test_expect_success 'off-order branch not found' ' > + ! git show-ref --verify --quiet refs/heads/b00 > +' Use test_must_fail() rather than '!' when expecting a Git command to fail. > +test_expect_success 'subsequent pack-refs fails' ' > + ! git pack-refs --all > +' Ditto.
On Wed, Jan 30, 2019 at 06:31:34PM -0500, Eric Sunshine wrote: > On Wed, Jan 30, 2019 at 6:21 PM Max Kirillov <max@max630.net> wrote: >> + strbuf_addf(err, "broken sorting in packed-refs: '%s' > '%s'", >> + prev_ref.buf, >> + iter->refname); > strbuf_release(&prev_ref) either here or after the "error" label. Thanks! I seem to forget about it. > > + git branch b$(printf "%02d" $num) || break > This should probably be "|| return 1" rather than "|| break" in order > to fail the test immediately. I've been looking for the correct way, and have seen the break somewhere. Now I see the "return 1" is mostly user. Thanks, will fix. > Use test_must_fail() rather than '!' when expecting a Git command to fail. Will fix in both places
On Thu, Jan 31 2019, Max Kirillov wrote: > If packed-refs is marked as sorted but not really sorted it causes > very hard to comprehend misbehavior of reference resolving - a reference > is reported as not found. > > As the scope of the issue is not clear, make it visible by failing > pack-refs command - the one which would not suffer performance penalty > to verify the sortedness - when it encounters not really sorted existing > data. > > Signed-off-by: Max Kirillov <max@max630.net> > --- > I happened to have a not really sorted packed-refs file. As you might guess, > it was quite wtf-ing experience. It worked, mostly, but there was one branch > which just did not resolve, regardless of existing and being presented in > for-each-refs output. > > I don't know where the corruption came from. I should admit it could even be a manual > editing but last time I did it (in that reporitory) was several years ago so it is unlikely. > > I am not sure what should be the proper fix. I did a minimal detection, so that > it does not go unnoticed. Probably next step would be either fixing in `git fsck` call. > > refs/packed-backend.c | 15 +++++++++++++++ > t/t3212-pack-refs-broken-sorting.sh | 26 ++++++++++++++++++++++++++ > 2 files changed, 41 insertions(+) > create mode 100755 t/t3212-pack-refs-broken-sorting.sh This is not an area I'm very familiar with. So mostly commeting on cosmetic issues with the patch. FWIW the "years back" issue you had could be that an issue didn't manifest until now, i.e. in a sorted file format you can get lucky and not see corruption for a while with a random insert. > diff --git a/refs/packed-backend.c b/refs/packed-backend.c > index c01c7f5901..505f4535b5 100644 > --- a/refs/packed-backend.c > +++ b/refs/packed-backend.c > @@ -1088,6 +1088,7 @@ static int write_with_updates(struct packed_ref_store *refs, > FILE *out; > struct strbuf sb = STRBUF_INIT; > char *packed_refs_path; > + struct strbuf prev_ref = STRBUF_INIT; > > if (!is_lock_file_locked(&refs->lock)) > BUG("write_with_updates() called while unlocked"); > @@ -1137,6 +1138,20 @@ static int write_with_updates(struct packed_ref_store *refs, > struct ref_update *update = NULL; > int cmp; > > + if (iter) > + { > + if (prev_ref.len && strcmp(prev_ref.buf, iter->refname) > 0) You have an extra two whitespaces after "&&" there. > + { > + strbuf_addf(err, "broken sorting in packed-refs: '%s' > '%s'", > + prev_ref.buf, > + iter->refname); > + goto error; > + } > + > + strbuf_init(&prev_ref, 0); > + strbuf_addstr(&prev_ref, iter->refname); > + } > + > if (i >= updates->nr) { > cmp = -1; > } else { > diff --git a/t/t3212-pack-refs-broken-sorting.sh b/t/t3212-pack-refs-broken-sorting.sh > new file mode 100755 > index 0000000000..37a98a6fb1 > --- /dev/null > +++ b/t/t3212-pack-refs-broken-sorting.sh > @@ -0,0 +1,26 @@ > +#!/bin/sh > + > +test_description='tests for the falsely sorted refs' > +. ./test-lib.sh > + > +test_expect_success 'setup' ' > + git commit --allow-empty -m commit && Looks like just "test_commit A" would do here. > + for num in $(test_seq 10) > + do > + git branch b$(printf "%02d" $num) || break > + done && We can fail in these sorts of loops. There's a few ways to deal with that. Doing it like this with "break" will still silently hide errors: $ for i in $(seq 1 3); do if test $i = 2; then false || break; else echo $i; fi; done && echo success 1 success One way to deal with that is to e.g. before the loop say "had_fail=", then set "had_fail=t" in that "||" case, and test for it after the loop. But perhaps in this case we're better off e.g. running for-each-ref after and either using test_cmp or test_line_count to see that we created the refs successfully? > + git pack-refs --all && > + head_object=$(git rev-parse HEAD) && > + printf "$head_object refs/heads/b00\\n" >>.git/packed-refs && Looks like just "echo" here would be simpler since we only use printf to add a newline. > + git branch b11 > +' > + > +test_expect_success 'off-order branch not found' ' > + ! git show-ref --verify --quiet refs/heads/b00 > +' > + > +test_expect_success 'subsequent pack-refs fails' ' > + ! git pack-refs --all > +' Instead of "! git ..." use "test_must_fail git ...". See t/README. This will hide e.g. segfaults. Also, perhaps: test_must_fail git ... 2>stderr && grep "broken sorting in packed-refs" stderr Would make this more obvious/self-documenting so we know we failed due to that issue in particular.
On Wed, Feb 13, 2019 at 11:08:01AM +0100, Ævar Arnfjörð Bjarmason wrote: > > On Thu, Jan 31 2019, Max Kirillov wrote: > > refs/packed-backend.c | 15 +++++++++++++++ > > t/t3212-pack-refs-broken-sorting.sh | 26 ++++++++++++++++++++++++++ > > 2 files changed, 41 insertions(+) > > create mode 100755 t/t3212-pack-refs-broken-sorting.sh > > This is not an area I'm very familiar with. So mostly commeting on > cosmetic issues with the patch. Just two quick comments in addition to Ævar's: > > @@ -1137,6 +1138,20 @@ static int write_with_updates(struct packed_ref_store *refs, > > struct ref_update *update = NULL; > > int cmp; > > > > + if (iter) > > + { According to our CodingGuidelines, the opening bracket should go on the same line as the condition, i.e. if (iter) { > > diff --git a/t/t3212-pack-refs-broken-sorting.sh b/t/t3212-pack-refs-broken-sorting.sh > > new file mode 100755 > > index 0000000000..37a98a6fb1 > > --- /dev/null > > +++ b/t/t3212-pack-refs-broken-sorting.sh > > @@ -0,0 +1,26 @@ > > +#!/bin/sh > > + > > +test_description='tests for the falsely sorted refs' > > +. ./test-lib.sh > > + > > +test_expect_success 'setup' ' > > + git commit --allow-empty -m commit && > > Looks like just "test_commit A" would do here. > > > + for num in $(test_seq 10) > > + do > > + git branch b$(printf "%02d" $num) || break > > + done && > > We can fail in these sorts of loops. There's a few ways to deal with > that. Doing it like this with "break" will still silently hide errors: > > $ for i in $(seq 1 3); do if test $i = 2; then false || break; else echo $i; fi; done && echo success > 1 > success > > One way to deal with that is to e.g. before the loop say "had_fail=", > then set "had_fail=t" in that "||" case, and test for it after the loop. No, you can simply do 'cmd1 && cmd2 || return 1' in the body of the for loop; that's why we have a separate test_eval_inner() helper function in test-lib.
On Wed, Feb 13, 2019 at 11:08:01AM +0100, Ævar Arnfjörð Bjarmason wrote: > > I happened to have a not really sorted packed-refs file. As you might guess, > > it was quite wtf-ing experience. It worked, mostly, but there was one branch > > which just did not resolve, regardless of existing and being presented in > > for-each-refs output. > > > > I don't know where the corruption came from. I should admit it could even be a manual > > editing but last time I did it (in that reporitory) was several years ago so it is unlikely. > > > > I am not sure what should be the proper fix. I did a minimal detection, so that > > it does not go unnoticed. Probably next step would be either fixing in `git fsck` call. > > > > refs/packed-backend.c | 15 +++++++++++++++ > > t/t3212-pack-refs-broken-sorting.sh | 26 ++++++++++++++++++++++++++ > > 2 files changed, 41 insertions(+) > > create mode 100755 t/t3212-pack-refs-broken-sorting.sh > > This is not an area I'm very familiar with. So mostly commeting on > cosmetic issues with the patch. FWIW the "years back" issue you had > could be that an issue didn't manifest until now, i.e. in a sorted file > format you can get lucky and not see corruption for a while with a > random insert. It actually shouldn't be that old a breakage. Until 02b920f3f7 (read_packed_refs(): ensure that references are ordered when read, 2017-09-25), we did not assume the file was sorted (even though we always wrote it out sorted). And we continue to not assume the file is sorted unless it is written out with an explicit "sorted" trait in the header (which we started doing in that commit, too). So a years-old manual edit would not have the "sorted" trait, and should not have manifested as a problem, even now. Likewise for a years-old bug. It would have to be a bug in a _new_ writer which writes out the sorted trait. If there is such a bug in our implementation, this would be the first report we've seen. Given the number of times pack-refs has been run, without further evidence I'm inclined to think it was some weird manual edit, or maybe an alternate implementation (though one would _hope_ they would not write out the sorted trait without actually sorting!). I agree with all of the cosmetic issues you mentioned. As far as what the patch itself does, I think it's OK. We could probably go further and actually sort it (or even just write it out without a "sorted" trait, which means the next read would load it all into memory and sort it). That's a little friendlier, since just dying leaves the user to fix it up themselves. But given that we expect this code to trigger approximately never, it's probably not worth spending much time on a fancy solution. -Peff
On Wed, Feb 13, 2019 at 11:08:01AM +0100, Ævar Arnfjörð Bjarmason wrote: > You have an extra two whitespaces after "&&" there. Thanks, will check it. >> + git commit --allow-empty -m commit && > Looks like just "test_commit A" would do here. About this I'm not sure. AFAIK test_commit does lots of stuff, so can it be considered "just" compared to "commit --allow-empty" or the opposite? I could replace it with test_commit for uniformity reason though. > We can fail in these sorts of loops. There's a few ways to deal with > that. Doing it like this with "break" will still silently hide errors: Thanks, this was pointed point >> + printf "$head_object refs/heads/b00\\n" >>.git/packed-refs && > > Looks like just "echo" here would be simpler since we only use printf to > add a newline. Could it happen so that "echo" adds '\r\n' at Windows? I could use echo. > Instead of "! git ..." use "test_must_fail git ...". See t/README. This > will hide e.g. segfaults. Thanks, this was pointed point > Also, perhaps: > > test_must_fail git ... 2>stderr && > grep "broken sorting in packed-refs" stderr > > Would make this more obvious/self-documenting so we know we failed due > to that issue in particular. Thanks, will change it
On Wed, Feb 13, 2019 at 11:56:16AM +0100, SZEDER Gábor wrote: >>> + if (iter) >>> + { > > According to our CodingGuidelines, the opening bracket should go on > the same line as the condition, i.e. > > if (iter) { Oh, thanks. I must have been professionally deformed.
diff --git a/refs/packed-backend.c b/refs/packed-backend.c index c01c7f5901..505f4535b5 100644 --- a/refs/packed-backend.c +++ b/refs/packed-backend.c @@ -1088,6 +1088,7 @@ static int write_with_updates(struct packed_ref_store *refs, FILE *out; struct strbuf sb = STRBUF_INIT; char *packed_refs_path; + struct strbuf prev_ref = STRBUF_INIT; if (!is_lock_file_locked(&refs->lock)) BUG("write_with_updates() called while unlocked"); @@ -1137,6 +1138,20 @@ static int write_with_updates(struct packed_ref_store *refs, struct ref_update *update = NULL; int cmp; + if (iter) + { + if (prev_ref.len && strcmp(prev_ref.buf, iter->refname) > 0) + { + strbuf_addf(err, "broken sorting in packed-refs: '%s' > '%s'", + prev_ref.buf, + iter->refname); + goto error; + } + + strbuf_init(&prev_ref, 0); + strbuf_addstr(&prev_ref, iter->refname); + } + if (i >= updates->nr) { cmp = -1; } else { diff --git a/t/t3212-pack-refs-broken-sorting.sh b/t/t3212-pack-refs-broken-sorting.sh new file mode 100755 index 0000000000..37a98a6fb1 --- /dev/null +++ b/t/t3212-pack-refs-broken-sorting.sh @@ -0,0 +1,26 @@ +#!/bin/sh + +test_description='tests for the falsely sorted refs' +. ./test-lib.sh + +test_expect_success 'setup' ' + git commit --allow-empty -m commit && + for num in $(test_seq 10) + do + git branch b$(printf "%02d" $num) || break + done && + git pack-refs --all && + head_object=$(git rev-parse HEAD) && + printf "$head_object refs/heads/b00\\n" >>.git/packed-refs && + git branch b11 +' + +test_expect_success 'off-order branch not found' ' + ! git show-ref --verify --quiet refs/heads/b00 +' + +test_expect_success 'subsequent pack-refs fails' ' + ! git pack-refs --all +' + +test_done
If packed-refs is marked as sorted but not really sorted it causes very hard to comprehend misbehavior of reference resolving - a reference is reported as not found. As the scope of the issue is not clear, make it visible by failing pack-refs command - the one which would not suffer performance penalty to verify the sortedness - when it encounters not really sorted existing data. Signed-off-by: Max Kirillov <max@max630.net> --- I happened to have a not really sorted packed-refs file. As you might guess, it was quite wtf-ing experience. It worked, mostly, but there was one branch which just did not resolve, regardless of existing and being presented in for-each-refs output. I don't know where the corruption came from. I should admit it could even be a manual editing but last time I did it (in that reporitory) was several years ago so it is unlikely. I am not sure what should be the proper fix. I did a minimal detection, so that it does not go unnoticed. Probably next step would be either fixing in `git fsck` call. refs/packed-backend.c | 15 +++++++++++++++ t/t3212-pack-refs-broken-sorting.sh | 26 ++++++++++++++++++++++++++ 2 files changed, 41 insertions(+) create mode 100755 t/t3212-pack-refs-broken-sorting.sh