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dyn-config: try to read it again in case the pagecache is not flushed out #548

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dyn-config: try to read it again in case the pagecache is not flushed out #548

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28 changes: 25 additions & 3 deletions libtcmu_config.c
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Original file line number Diff line number Diff line change
Expand Up @@ -195,7 +195,7 @@ static void tcmu_conf_set_options(struct tcmu_config *cfg)
}

#define TCMU_MAX_CFG_FILE_SIZE (2 * 1024 * 1024)
static int tcmu_read_config(int fd, char *buf, int count)
static int tcmu_read_config(int fd, char *buf, int count, int *err)
{
ssize_t len;
int save = errno;
Expand All @@ -204,6 +204,7 @@ static int tcmu_read_config(int fd, char *buf, int count)
len = read(fd, buf, count);
} while (errno == EAGAIN);

*err = -errno;
errno = save;
return len;
}
Expand Down Expand Up @@ -355,12 +356,14 @@ int tcmu_load_config(struct tcmu_config *cfg)
int ret = -1;
int fd, len;
char *buf;
int i;
int i, count = 0;

buf = malloc(TCMU_MAX_CFG_FILE_SIZE);
if (!buf)
return -ENOMEM;

retry:
count++;
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I think the tabbing/spacing got messed up for the count++ line.

for (i = 0; i < 5; i++) {
if ((fd = open(TCMU_CONFIG_FILE_DEFAULT, O_RDONLY)) == -1) {
/* give a moment for editor to restore
Expand All @@ -376,8 +379,27 @@ int tcmu_load_config(struct tcmu_config *cfg)
goto free_buf;
}

len = tcmu_read_config(fd, buf, TCMU_MAX_CFG_FILE_SIZE);
len = tcmu_read_config(fd, buf, TCMU_MAX_CFG_FILE_SIZE, &ret);
close(fd);

/*
* In-case if the editor (vim) follows write to a new file (.swp, .tmp ..)
* and move it to actual file name later. There is a window, where we will
* encounter one case that the file data is not flushed to the disk, so in
* another process(here) when reading it will be empty.
*
* And at the same time the old file maybe deleted, then the read will failed
* with errno == ENOENT.
*
* Let just wait and try again.
*/
if (count <= 5 && (len == 0 || ret == -ENOENT)) {
tcmu_dbg("failed to read the config from file, retrying (%d/5) times\n",
count);
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Same for the "count);" line here. I think the tabbing/spacing got messed up.

sleep(1);
goto retry;
}

if (len < 0) {
tcmu_err("Failed to read file '%s'\n", TCMU_CONFIG_FILE_DEFAULT);
goto free_buf;
Expand Down