[PATCH v3 12/23] log_ref_setup(): improve robustness against races
- From
Michael Haggerty <mhagger@alum.mit.edu>
- Date
- Dec 31, 2016, 03:12 UTC
- Message-ID
- <9ab4c213af5e342e0bfd6bc7a120c6fbd42d9538.1483153436.git.mhagger@alum.mit.edu>
- In-Reply-To
- <cover.1483153436.git.mhagger@alum.mit.edu>
Change log_ref_setup() to use raceproof_create_file() to create the new logfile. This makes it more robust against a race against another process that might be trying to clean up empty directories while we are trying to create a new logfile.
This also means that it will only call create_leading_directories() if open() fails, which should be a net win. Even in the cases where we are willing to create a new logfile, it will usually be the case that the logfile already exists, or if not then that the directory containing the logfile already exists. In such cases, we will save some work that was previously done unconditionally.
Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> --- refs/files-backend.c | 41 ++++++++++++++++++----------------------- 1 file changed, 18 insertions(+), 23 deletions(-)
diff --git a/refs/files-backend.c b/refs/files-backend.c index 47c7829..345f7c3 100644 --- a/refs/files-backend.c +++ b/refs/files-backend.c @@ -2710,6 +2710,14 @@ static int commit_ref(struct ref_lock *lock) return 0; } +static int open_or_create_logfile(const char *path, void *cb) +{ + int *fd = cb; + + *fd = open(path, O_APPEND | O_WRONLY | O_CREAT, 0666); + return (*fd < 0) ? -1 : 0; +} + /* * Create a reflog for a ref. If force_create = 0, the reflog will * only be created for certain refs (those for which @@ -2723,31 +2731,18 @@ static int log_ref_setup(const char *refname, struct strbuf *logfile, struct str strbuf_git_path(logfile, "logs/%s", refname); if (force_create || should_autocreate_reflog(refname)) { - if (safe_create_leading_directories(logfile->buf) < 0) { - strbuf_addf(err, "unable to create directory for '%s': " - "%s", logfile->buf, strerror(errno)); - return -1; - } - logfd = open(logfile->buf, O_APPEND | O_WRONLY | O_CREAT, 0666); - if (logfd < 0) { - if (errno == EISDIR) { - /* - * The directory that is in the way might be - * empty. Try to remove it. - */ - if (remove_empty_directories(logfile)) { - strbuf_addf(err, "there are still logs under " - "'%s'", logfile->buf); - return -1; - } - logfd = open(logfile->buf, O_APPEND | O_WRONLY | O_CREAT, 0666); - } - - if (logfd < 0) { + if (raceproof_create_file(logfile->buf, open_or_create_logfile, &logfd)) { + if (errno == ENOENT) + strbuf_addf(err, "unable to create directory for '%s': " + "%s", logfile->buf, strerror(errno)); + else if (errno == EISDIR) + strbuf_addf(err, "there are still logs under '%s'", + logfile->buf); + else strbuf_addf(err, "unable to append to '%s': %s", logfile->buf, strerror(errno)); - return -1; - } + + return -1; } } else { logfd = open(logfile->buf, O_APPEND | O_WRONLY, 0666);
-- 2.9.3