Re: [PATCH 2/2] A loose object is not corrupt if it cannot be read due to EMFILE
- From
Erik Faye-Lund <kusmabite@gmail.com>
- Date
- Nov 18, 2010, 14:19 UTC
- Message-ID
- <AANLkTi=L1Z6kxubMf3yPUfpY9ugd+Qan+yCxi3dp4oR4@mail.gmail.com>
- In-Reply-To
- <1288299210-27092-2-git-send-email-gitster@pobox.com>
On Thu, Oct 28, 2010 at 10:53 PM, Junio C Hamano <gitster@pobox.com> wrote:
Show 44 quoted lines
> "git fsck" bails out with a claim that a loose object that cannot be
> read but exists on the filesystem to be corrupt, which is wrong when
> read_object() failed due to e.g. EMFILE.
>
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> ---
> sha1_file.c | 7 ++++++-
> 1 files changed, 6 insertions(+), 1 deletions(-)
>
> diff --git a/sha1_file.c b/sha1_file.c
> index 5ed5497..f709ed6 100644
> --- a/sha1_file.c
> +++ b/sha1_file.c
> @@ -2090,16 +2090,21 @@ void *read_sha1_file_repl(const unsigned char *sha1,
> const unsigned char **replacement)
> {
> const unsigned char *repl = lookup_replace_object(sha1);
> - void *data = read_object(repl, type, size);
> + void *data;
> char *path;
> const struct packed_git *p;
>
> + errno = 0;
> + data = read_object(repl, type, size);
> if (data) {
> if (replacement)
> *replacement = repl;
> return data;
> }
>
> + if (errno != ENOENT)
> + die_errno("failed to read object %s", sha1_to_hex(sha1));
> +
> /* die if we replaced an object with one that does not exist */
> if (repl != sha1)
> die("replacement %s not found for %s",
> --
> 1.7.3.2.191.g2d0e57
>
> --
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>This patch seems to break clone/fetch on Windows:
$ GIT_TRACE=1 git clone http://github.com/kusma/rocket.git clone-test trace: built-in: git 'clone' 'http://github.com/kusma/rocket.git' 'clone-test' Cloning into clone-test... trace: run_command: 'git-remote-http' 'origin' 'http://github.com/kusma/rocket.git' trace: run_command: 'fetch-pack' '--stateless-rpc' '--lock-pack' '--thin' 'http://github.com/kusma/rocket.git/' 'refs/heads/master' 'refs/heads/work/icon' 'refs/heads/work/io-callback' 'refs/heads/work/sdl-example' 'refs/tags/v0.8' trace: built-in: git 'fetch-pack' '--stateless-rpc' '--lock-pack' '--thin' 'http://github.com/kusma/rocket.git/' 'refs/heads/master' 'refs/heads/work/icon' 'refs/heads/work/io-callback' 'refs/heads/work/sdl-example' 'refs/tags/v0.8' fatal: failed to read object 7ea7cabd967429886c26e78b3ec573d54a95fa9d: No error fatal: The remote end hung up unexpectedly
What happens, is that read_object returns NULL, but errno is 0. Further, it looks to me like read_object can only return NULL through the unpack_sha1_file (problem with the compressed data) or read_packed_sha1 (find_pack_entry() failure) code-paths.
errno is set to ENOENT by open_sha1_file (through map_sha1_file) before any possible error-points. I guess this makes the "errno = 0" redundant, but I think it improves readability of the code. I'm guessing that errno gets overwritten by some other call, losing the ENOENT. Perhaps some unintended side-effect of one of the compat/mingw.[ch]-wrappers?
I did find such a case, but fixing it doesn't do the trick for me:
---8<---
diff --git a/compat/mingw.c b/compat/mingw.c index 29f4036..fdbf093 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -198,9 +198,10 @@ static inline time_t filetime_to_time_t(const FILETIME *ft) */ static int do_lstat(int follow, const char *file_name, struct stat *buf) { + int err; WIN32_FILE_ATTRIBUTE_DATA fdata; - if (!(errno = get_file_attr(file_name, &fdata))) { + if (!(err = get_file_attr(file_name, &fdata))) { buf->st_ino = 0; buf->st_gid = 0; buf->st_uid = 0; @@ -233,6 +234,7 @@ static int do_lstat(int follow, const char *file_name, struct stat *buf) } return 0; } + errno = err; return -1; } ---8<--- The following patch makes clone complete again, but I doubt it's the right solution. However, I'm out of ideas for now. Anyone? :) diff --git a/sha1_file.c b/sha1_file.c index 25f6965..9d4cb9c 100644 --- a/sha1_file.c +++ b/sha1_file.c @@ -2102,7 +2102,7 @@ void *read_sha1_file_repl(const unsigned char *sha1, return data; } - if (errno != ENOENT) + if (errno && errno != ENOENT) die_errno("failed to read object %s", sha1_to_hex(sha1)); /* die if we replaced an object with one that does not exist */