On Fri, Apr 30, 2021 at 06:40:32PM -0300, Matheus Tavares wrote:
> Add tests to confirm that path collisions are properly detected by
> checkout workers, both to avoid race conditions and to report colliding
> entries on clone.
>
> Co-authored-by: Jeff Hostetler <jeffhost@xxxxxxxxxxxxx>
> Signed-off-by: Matheus Tavares <matheus.bernardino@xxxxxx>
> ---
> parallel-checkout.c | 4 +
> t/lib-parallel-checkout.sh | 4 +-
> t/t2081-parallel-checkout-collisions.sh | 162 ++++++++++++++++++++++++
> 3 files changed, 168 insertions(+), 2 deletions(-)
> create mode 100755 t/t2081-parallel-checkout-collisions.sh
>
> diff --git a/parallel-checkout.c b/parallel-checkout.c
> index 09e8b10a35..6fb3f1e6c9 100644
> --- a/parallel-checkout.c
> +++ b/parallel-checkout.c
> @@ -8,6 +8,7 @@
> #include "sigchain.h"
> #include "streaming.h"
> #include "thread-utils.h"
> +#include "trace2.h"
>
> struct pc_worker {
> struct child_process cp;
> @@ -326,6 +327,7 @@ void write_pc_item(struct parallel_checkout_item *pc_item,
> if (dir_sep && !has_dirs_only_path(path.buf, dir_sep - path.buf,
> state->base_dir_len)) {
> pc_item->status = PC_ITEM_COLLIDED;
> + trace2_data_string("pcheckout", NULL, "collision/dirname", path.buf);
> goto out;
> }
>
> @@ -341,6 +343,8 @@ void write_pc_item(struct parallel_checkout_item *pc_item,
> * call should have already caught these cases.
> */
> pc_item->status = PC_ITEM_COLLIDED;
> + trace2_data_string("pcheckout", NULL,
> + "collision/basename", path.buf);
> } else {
> error_errno("failed to open file '%s'", path.buf);
> pc_item->status = PC_ITEM_FAILED;
> diff --git a/t/lib-parallel-checkout.sh b/t/lib-parallel-checkout.sh
> index f60b22ef34..d6740425b1 100644
> --- a/t/lib-parallel-checkout.sh
> +++ b/t/lib-parallel-checkout.sh
> @@ -22,12 +22,12 @@ test_checkout_workers () {
>
> local trace_file=trace-test-checkout-workers &&
> rm -f "$trace_file" &&
> - GIT_TRACE2="$(pwd)/$trace_file" "$@" &&
> + GIT_TRACE2="$(pwd)/$trace_file" "$@" 2>&8 &&
>
> local workers=$(grep "child_start\[..*\] git checkout--worker" "$trace_file" | wc -l) &&
> test $workers -eq $expected_workers &&
> rm "$trace_file"
> -}
> +} 8>&2 2>&4
>
> # Verify that both the working tree and the index were created correctly
> verify_checkout () {
> diff --git a/t/t2081-parallel-checkout-collisions.sh b/t/t2081-parallel-checkout-collisions.sh
> new file mode 100755
> index 0000000000..f6fcfc0c1e
> --- /dev/null
> +++ b/t/t2081-parallel-checkout-collisions.sh
> @@ -0,0 +1,162 @@
> +#!/bin/sh
> +
> +test_description="path collisions during parallel checkout
> +
> +Parallel checkout must detect path collisions to:
> +
> +1) Avoid racily writing to different paths that represent the same file on disk.
> +2) Report the colliding entries on clone.
> +
> +The tests in this file exercise parallel checkout's collision detection code in
> +both these mechanics.
> +"
> +
> +. ./test-lib.sh
> +. "$TEST_DIRECTORY/lib-parallel-checkout.sh"
Why this $TEST_DIRECTORY ?
Aren't all files under the t/ directory, where test-lib.sh is as well ?
(The $TEST_DIRECTORY macro is used at different places, so I may have missed
something)
> +
> +TEST_ROOT="$PWD"
> +
> +test_expect_success CASE_INSENSITIVE_FS 'setup' '
> + empty_oid=$(git hash-object -w --stdin </dev/null) &&
> + cat >objs <<-EOF &&
> + 100644 $empty_oid FILE_X
> + 100644 $empty_oid FILE_x
> + 100644 $empty_oid file_X
> + 100644 $empty_oid file_x
> + EOF
> + git update-index --index-info <objs &&
> + git commit -m "colliding files" &&
> + git tag basename_collision &&
> +
> + write_script "$TEST_ROOT"/logger_script <<-\EOF
> + echo "$@" >>filter.log
> + EOF
> +'
> +
> +test_workers_in_event_trace ()
> +{
> + test $1 -eq $(grep ".event.:.child_start..*checkout--worker" $2 | wc -l)
> +}
> +
> +test_expect_success CASE_INSENSITIVE_FS 'worker detects basename collision' '
> + GIT_TRACE2_EVENT="$(pwd)/trace" git \
> + -c checkout.workers=2 -c checkout.thresholdForParallelism=0 \
> + checkout . &&
> +
> + test_workers_in_event_trace 2 trace &&
> + collisions=$(grep -i "category.:.pcheckout.,.key.:.collision/basename.,.value.:.file_x.}" trace | wc -l) &&
> + test $collisions -eq 3
> +'
> +
> +test_expect_success CASE_INSENSITIVE_FS 'worker detects dirname collision' '
> + test_config filter.logger.smudge "\"$TEST_ROOT/logger_script\" %f" &&
> + empty_oid=$(git hash-object -w --stdin </dev/null) &&
> +
> + # By setting a filter command to "a", we make it ineligible for parallel
> + # checkout, and thus it is checked out *first*. This way we can ensure
> + # that "A/B" and "A/C" will both collide with the regular file "a".
> + #
> + attr_oid=$(echo "a filter=logger" | git hash-object -w --stdin) &&
> +
> + cat >objs <<-EOF &&
> + 100644 $empty_oid A/B
> + 100644 $empty_oid A/C
> + 100644 $empty_oid a
> + 100644 $attr_oid .gitattributes
> + EOF
> + git rm -rf . &&
> + git update-index --index-info <objs &&
> +
> + rm -f trace filter.log &&
> + GIT_TRACE2_EVENT="$(pwd)/trace" git \
> + -c checkout.workers=2 -c checkout.thresholdForParallelism=0 \
> + checkout . &&
> +
> + # Check that "a" (and only "a") was filtered
> + echo a >expected.log &&
> + test_cmp filter.log expected.log &&
> +
> + # Check that it used the right number of workers and detected the collisions
> + test_workers_in_event_trace 2 trace &&
> + grep "category.:.pcheckout.,.key.:.collision/dirname.,.value.:.A/B.}" trace &&
> + grep "category.:.pcheckout.,.key.:.collision/dirname.,.value.:.A/C.}" trace
> +'
> +
> +test_expect_success SYMLINKS,CASE_INSENSITIVE_FS 'do not follow symlinks colliding with leading dir' '
> + empty_oid=$(git hash-object -w --stdin </dev/null) &&
> + symlink_oid=$(echo "./e" | git hash-object -w --stdin) &&
> + mkdir e &&
> +
> + cat >objs <<-EOF &&
> + 120000 $symlink_oid D
> + 100644 $empty_oid d/x
> + 100644 $empty_oid e/y
> + EOF
> + git rm -rf . &&
> + git update-index --index-info <objs &&
> +
> + set_checkout_config 2 0 &&
> + test_checkout_workers 2 git checkout . &&
> + test_path_is_dir e &&
> + test_path_is_missing e/x
> +'
> +
> +# The two following tests check that parallel checkout correctly reports
> +# colliding entries on clone. The sequential code detects a collision by
> +# calling lstat() before trying to open(O_CREAT) a file. (Note that this only
> +# works for clone.) Then, to find the pair of a colliding item k, it searches
> +# cache_entry[0, k-1]. This is not sufficient in parallel checkout because:
> +#
> +# - A colliding file may be created between the lstat() and open() calls;
> +# - A colliding entry might appear in the second half of the cache_entry array.
> +#
> +test_expect_success CASE_INSENSITIVE_FS 'collision report on clone (w/ racy file creation)' '
> + git reset --hard basename_collision &&
> + set_checkout_config 2 0 &&
> + test_checkout_workers 2 git clone . clone-repo 2>stderr &&
> +
> + grep FILE_X stderr &&
> + grep FILE_x stderr &&
> + grep file_X stderr &&
> + grep file_x stderr &&
> + grep "the following paths have collided" stderr
> +'
> +
> +# This test ensures that the collision report code is correctly looking for
> +# colliding peers in the second half of the cache_entry array. This is done by
> +# defining a smudge command for the *last* array entry, which makes it
> +# non-eligible for parallel-checkout. Thus, it is checked out *first*, before
> +# spawning the workers.
> +#
> +# Note: this test doesn't work on Windows because, on this system, the
> +# collision report code uses strcmp() to find the colliding pairs when
> +# core.ignoreCase is false. And we need this setting for this test so that only
> +# 'file_x' matches the pattern of the filter attribute. But the test works on
> +# OSX, where the colliding pairs are found using inode.
> +#
> +test_expect_success CASE_INSENSITIVE_FS,!MINGW,!CYGWIN \
> + 'collision report on clone (w/ colliding peer after the detected entry)' '
> +
> + test_config_global filter.logger.smudge "\"$TEST_ROOT/logger_script\" %f" &&
> + git reset --hard basename_collision &&
> + echo "file_x filter=logger" >.gitattributes &&
> + git add .gitattributes &&
> + git commit -m "filter for file_x" &&
> +
> + rm -rf clone-repo &&
> + set_checkout_config 2 0 &&
> + test_checkout_workers 2 \
> + git -c core.ignoreCase=false clone . clone-repo 2>stderr &&
> +
> + grep FILE_X stderr &&
> + grep FILE_x stderr &&
> + grep file_X stderr &&
> + grep file_x stderr &&
> + grep "the following paths have collided" stderr &&
> +
> + # Check that only "file_x" was filtered
> + echo file_x >expected.log &&
> + test_cmp clone-repo/filter.log expected.log
> +'
> +
> +test_done
> --
> 2.30.1
>
