Daniel Barkalow <barkalow@xxxxxxxxxxxx> 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 <barkalow@xxxxxxxxxxxx>
> ---
> 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;
--
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