Re: [PATCH 2/8] Add a lockfile function to append to a file
From: Junio C Hamano <hidden>
Date: 2016-06-15 22:44:30
Subsystem:
the rest · Maintainer:
Linus Torvalds
Possibly related (same subject, not in this thread)
- 2016-06-15 · [PATCH 2/8] Add a lockfile function to append to a file · Daniel Barkalow <hidden>
- 2016-06-15 · Re: [PATCH 2/8] Add a lockfile function to append to a file · Junio C Hamano <hidden>
- 2016-06-15 · Re: [PATCH 2/8] Add a lockfile function to append to a file · Junio C Hamano <hidden>
- 2016-06-15 · [PATCH 2/8] Add a lockfile function to append to a file · Daniel Barkalow <hidden>
Daniel Barkalow [off-list ref] writes:
This takes care of copying the original contents into the replacement file after the lock is held, so that concurrent additions can't miss each other's changes. Signed-off-by: Daniel Barkalow <redacted> --- How about this? Also doesn't leak a fd and catches trying to append to a file you can't read. Should I worry about mmap failing after the open?
We have copy.c to copy small existing files, while detecting failure to copy properly. How about doing something like this instead? cache.h | 1 + lockfile.c | 28 ++++++++++++++++++++++++++++ 2 files changed, 29 insertions(+), 0 deletions(-)
diff --git a/cache.h b/cache.h
index 50b28fa..8d066bf 100644
--- a/cache.h
+++ b/cache.h@@ -391,6 +391,7 @@ struct lock_file { char filename[PATH_MAX]; }; extern int hold_lock_file_for_update(struct lock_file *, const char *path, int); +extern int hold_lock_file_for_append(struct lock_file *, const char *path, int); extern int commit_lock_file(struct lock_file *); extern int hold_locked_index(struct lock_file *, int);
diff --git a/lockfile.c b/lockfile.c
index 663f18f..e9e0095 100644
--- a/lockfile.c
+++ b/lockfile.c@@ -160,6 +160,34 @@ int hold_lock_file_for_update(struct lock_file *lk, const char *path, int die_on return fd; } +int hold_lock_file_for_append(struct lock_file *lk, const char *path, int die_on_error) +{ + int fd, orig_fd; + + fd = lock_file(lk, path); + if (fd < 0) { + if (die_on_error) + die("unable to create '%s.lock': %s", path, strerror(errno)); + return fd; + } + + orig_fd = open(path, O_RDONLY); + if (orig_fd < 0) { + if (errno != ENOENT) { + if (die_on_error) + die("cannot open '%s' for copying", path); + close(fd); + return error("cannot open '%s' for copying", path); + } + } else if (copy_fd(orig_fd, fd)) { + if (die_on_error) + exit(128); + close(fd); + return -1; + } + return fd; +} + int close_lock_file(struct lock_file *lk) { int fd = lk->fd;