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2023-12-11reftable/stack: fix use of unseeded randomnessPatrick Steinhardt
When writing a new reftable stack, Git will first create the stack with a random suffix so that concurrent updates will not try to write to the same file. This random suffix is computed via a call to rand(3P). But we never seed the function via srand(3P), which means that the suffix is in fact always the same. Fix this bug by using `git_rand()` instead, which does not need to be initialized. While this function is likely going to be slower depending on the platform, this slowness should not matter in practice as we only use it when writing a new reftable stack. Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-11reftable/stack: fix stale lock when dyingPatrick Steinhardt
When starting a transaction via `reftable_stack_init_addition()`, we create a lockfile for the reftable stack itself which we'll write the new list of tables to. But if we terminate abnormally e.g. via a call to `die()`, then we do not remove the lockfile. Subsequent executions of Git which try to modify references will thus fail with an out-of-date error. Fix this bug by registering the lock as a `struct tempfile`, which ensures automatic cleanup for us. Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-11reftable/stack: reuse buffers when reloading stackPatrick Steinhardt
In `reftable_stack_reload_once()` we iterate over all the tables added to the stack in order to figure out whether any of the tables needs to be reloaded. We use a set of buffers in this context to compute the paths of these tables, but discard those buffers on every iteration. This is quite wasteful given that we do not need to transfer ownership of the allocated buffer outside of the loop. Refactor the code to instead reuse the buffers to reduce the number of allocations we need to do. Note that we do not have to manually reset the buffer because `stack_filename()` does this for us already. Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-11reftable/stack: perform auto-compaction with transactional interfacePatrick Steinhardt
Whenever updating references or reflog entries in the reftable stack, we need to add a new table to the stack, thus growing the stack's length by one. The stack can grow to become quite long rather quickly, leading to performance issues when trying to read records. But besides performance issues, this can also lead to exhaustion of file descriptors very rapidly as every single table requires a separate descriptor when opening the stack. While git-pack-refs(1) fixes this issue for us by merging the tables, it runs too irregularly to keep the length of the stack within reasonable limits. This is why the reftable stack has an auto-compaction mechanism: `reftable_stack_add()` will call `reftable_stack_auto_compact()` after its added the new table, which will auto-compact the stack as required. But while this logic works alright for `reftable_stack_add()`, we do not do the same in `reftable_addition_commit()`, which is the transactional equivalent to the former function that allows us to write multiple updates to the stack atomically. Consequentially, we will easily run into file descriptor exhaustion in code paths that use many separate transactions like e.g. non-atomic fetches. Fix this issue by calling `reftable_stack_auto_compact()`. Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-11reftable: handle interrupted writesPatrick Steinhardt
There are calls to write(3P) where we don't properly handle interrupts. Convert them to use `write_in_full()`. Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2023-12-11reftable: handle interrupted readsPatrick Steinhardt
There are calls to pread(3P) and read(3P) where we don't properly handle interrupts. Convert them to use `pread_in_full()` and `read_in_full()`, respectively. Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-02-16Merge branch 'hn/reftable-coverity-fixes'Junio C Hamano
Problems identified by Coverity in the reftable code have been corrected. * hn/reftable-coverity-fixes: reftable: add print functions to the record types reftable: make reftable_record a tagged union reftable: remove outdated file reftable.c reftable: implement record equality generically reftable: make reftable-record.h function signatures const correct reftable: handle null refnames in reftable_ref_record_equal reftable: drop stray printf in readwrite_test reftable: order unittests by complexity reftable: all xxx_free() functions accept NULL arguments reftable: fix resource warning reftable: ignore remove() return value in stack_test.c reftable: check reftable_stack_auto_compact() return value reftable: fix resource leak blocksource.c reftable: fix resource leak in block.c error path reftable: fix OOB stack write in print functions
2022-01-20reftable: fix resource warningHan-Wen Nienhuys
This would trigger in the unlikely event that we are compacting, and the next available file handle is 0. Signed-off-by: Han-Wen Nienhuys <hanwen@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-12-23reftable: support preset file mode for writingHan-Wen Nienhuys
Create files with mode 0666, so umask works as intended. Provides an override, which is useful to support shared repos (test t1301-shared-repo.sh). Signed-off-by: Han-Wen Nienhuys <hanwen@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-10-08reftable: implement stack, a mutable database of reftable files.Han-Wen Nienhuys
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>