sysfs: add function for writing to sysfs fd

Proposed function sysfs_wrte_descriptor() unifies error handling for
write() done to sysfs files. Main purpose is to use it with MD sysfs
file but it can be used elsewhere.

No functional changes.

Signed-off-by: Mariusz Tkaczyk <mariusz.tkaczyk@linux.intel.com>

6 files changed, 101 insertions, 56 deletions

diff --git a/Manage.c b/Manage.c
index aba97df8..0f232a57 100644
--- a/Manage.c
+++ b/Manage.c
@@ -1439,7 +1439,7 @@ int Manage_subdevs(char *devname, int fd,
 
 	for (dv = devlist; dv; dv = dv->next) {
 		dev_t rdev = 0; /* device to add/remove etc */
-		int rv;
+		int rv, err = 0;
 		int mj,mn;
 
 		raid_slot = -1;
@@ -1670,9 +1670,8 @@ int Manage_subdevs(char *devname, int fd,
 				rv = Manage_remove(tst, fd, dv, sysfd,
 						   rdev, verbose, force,
 						   devname);
-			if (sysfd >= 0)
-				close_fd(&sysfd);
-			sysfd = -1;
+			close_fd(&sysfd);
+
 			if (rv < 0)
 				goto abort;
 			if (rv > 0)
@@ -1686,23 +1685,31 @@ int Manage_subdevs(char *devname, int fd,
 				close_fd(&sysfd);
 				goto abort;
 			}
-		case 'I': /* incremental fail */
-			if ((sysfd >= 0 && write(sysfd, "faulty", 6) != 6) ||
-			    (sysfd < 0 && ioctl(fd, SET_DISK_FAULTY,
-						rdev))) {
-				if (errno == EBUSY)
-					busy = 1;
-				pr_err("set device faulty failed for %s:  %s\n",
-					dv->devname, strerror(errno));
-				close_fd(&sysfd);
-				goto abort;
+		case 'I':
+			if (is_fd_valid(sysfd)) {
+				static const char val[] = "faulty";
+
+				rv = sysfs_write_descriptor(sysfd, val, strlen(val), &err);
+			} else {
+				rv = ioctl(fd, SET_DISK_FAULTY, rdev);
+				if (rv)
+					err = errno;
 			}
+
 			close_fd(&sysfd);
-			count++;
-			if (verbose >= 0)
-				pr_err("set %s faulty in %s\n",
-					dv->devname, devname);
-			break;
+
+			if (rv == MDADM_STATUS_SUCCESS) {
+				count++;
+
+				pr_vrb("set %s faulty in %s\n", dv->devname, devname);
+				break;
+			}
+
+			if (err == EBUSY)
+				busy = 1;
+
+			pr_err("set device faulty failed for %s: %s\n", dv->devname, strerror(err));
+			goto abort;
 		case 'R': /* Mark as replaceable */
 			if (subarray) {
 				pr_err("Cannot replace disks in a \'member\' array, perform this operation on the parent container\n");
diff --git a/managemon.c b/managemon.c
index add6a79e..877e8605 100644
--- a/managemon.c
+++ b/managemon.c
@@ -512,16 +512,9 @@ static void manage_member(struct mdstat_ent *mdstat,
 	if (a->container == NULL)
 		return;
 
-	if (sigterm && a->info.safe_mode_delay != 1 &&
-	    a->safe_mode_delay_fd >= 0) {
-		long int new_delay = 1;
-		char delay[10];
-		ssize_t len;
-
-		len = snprintf(delay, sizeof(delay), "0.%03ld\n", new_delay);
-		if (write(a->safe_mode_delay_fd, delay, len) == len)
-			a->info.safe_mode_delay = new_delay;
-	}
+	if (sigterm && a->info.safe_mode_delay != 1 && a->safe_mode_delay_fd >= 0)
+		if (write_attr("0.001", a->safe_mode_delay_fd) == MDADM_STATUS_SUCCESS)
+			a->info.safe_mode_delay = 1;
 
 	/* We don't check the array while any update is pending, as it
 	 * might container a change (such as a spare assignment) which
diff --git a/mdadm.h b/mdadm.h
index d4f5702c..ce8155b5 100644
--- a/mdadm.h
+++ b/mdadm.h
@@ -803,6 +803,9 @@ enum sysfs_read_flags {
 
 #define SYSFS_MAX_BUF_SIZE 64
 
+extern mdadm_status_t sysfs_write_descriptor(const int fd, const char *value,
+					     const ssize_t len, int *errno_p);
+extern mdadm_status_t write_attr(const char *value, const int fd);
 extern void sysfs_get_container_devnm(struct mdinfo *mdi, char *buf);
 
 /* If fd >= 0, get the array it is open on,
diff --git a/monitor.c b/monitor.c
index be0bec78..a4f707cc 100644
--- a/monitor.c
+++ b/monitor.c
@@ -35,11 +35,6 @@ enum bb_action {
 	COMPARE_BB,
 };
 
-static int write_attr(char *attr, int fd)
-{
-	return write(fd, attr, strlen(attr));
-}
-
 static void add_fd(fd_set *fds, int *maxfd, int fd)
 {
 	struct stat st;
@@ -173,7 +168,7 @@ int process_ubb(struct active_array *a, struct mdinfo *mdi, const unsigned long
 	 * via sysfs file
 	 */
 	if ((ss->record_bad_block(a, mdi->disk.raid_disk, sector, length)) &&
-	    (write(mdi->bb_fd, buf, buf_len) == buf_len))
+	    (sysfs_write_descriptor(mdi->bb_fd, buf, buf_len, NULL) == MDADM_STATUS_SUCCESS))
 		return 1;
 
 	/*
@@ -622,14 +617,11 @@ static int read_and_act(struct active_array *a, fd_set *fds)
 		}
 
 		if ((mdi->next_state & DS_REMOVE) && mdi->state_fd >= 0) {
-			int remove_result;
-
 			/* The kernel may not be able to immediately remove the
 			 * disk.  In that case we wait a little while and
 			 * try again.
 			 */
-			remove_result = write_attr("remove", mdi->state_fd);
-			if (remove_result > 0) {
+			if (write_attr("remove", mdi->state_fd) == MDADM_STATUS_SUCCESS) {
 				dprintf_cont(" %d:removed", mdi->disk.raid_disk);
 				close(mdi->state_fd);
 				close(mdi->recovery_fd);
diff --git a/sysfs.c b/sysfs.c
index b3c8b10d..7a81cc5b 100644
--- a/sysfs.c
+++ b/sysfs.c
@@ -73,6 +73,47 @@ void sysfs_free(struct mdinfo *sra)
 		sra = sra2;
 	}
 }
+/**
+ * write_attr() - write value to fd, don't check errno.
+ * @attr: value to write.
+ * @fd: file descriptor write to.
+ *
+ * Size to write is calculated by strlen().
+ */
+mdadm_status_t write_attr(const char *value, const int fd)
+{
+	return sysfs_write_descriptor(fd, value, strlen(value), NULL);
+}
+
+/**
+ * sysfs_write_descriptor()- wrapper for write(), projected to be used with sysfs.
+ * @fd: file descriptor.
+ * @value: value to set.
+ * @len: length of the value.
+ * @errno_p: On write() failure, buffer to copy errno value, might be NULL.
+ *
+ * Errors are differentiated, because (at least theoretically) kernel may not process whole string
+ * and it may or may not be a problem (it depends on implementation in kernel). Decision belongs to
+ * caller then.
+ * Generally, it should be safe to check if @errno_p changed to determine if error occurred.
+ */
+mdadm_status_t sysfs_write_descriptor(const int fd, const char *value, const ssize_t len,
+				      int *errno_p)
+{
+	ssize_t ret;
+
+	ret = write(fd, value, len);
+	if (ret == -1) {
+		if (errno_p)
+			*errno_p = errno;
+		return MDADM_STATUS_ERROR;
+	}
+
+	if (ret != len)
+		return MDADM_STATUS_UNDEF;
+
+	return MDADM_STATUS_SUCCESS;
+}
 
 /**
  * sysfs_get_container_devnm() - extract container device name.
@@ -486,7 +527,6 @@ int sysfs_set_str(struct mdinfo *sra, struct mdinfo *dev,
 		  char *name, char *val)
 {
 	char fname[MAX_SYSFS_PATH_LEN];
-	unsigned int n;
 	int fd;
 
 	snprintf(fname, MAX_SYSFS_PATH_LEN, "/sys/block/%s/md/%s/%s",
@@ -494,13 +534,14 @@ int sysfs_set_str(struct mdinfo *sra, struct mdinfo *dev,
 	fd = open(fname, O_WRONLY);
 	if (fd < 0)
 		return -1;
-	n = write(fd, val, strlen(val));
-	close(fd);
-	if (n != strlen(val)) {
-		dprintf("failed to write '%s' to '%s' (%s)\n",
-			val, fname, strerror(errno));
+
+	if (write_attr(val, fd)) {
+		pr_err("failed to write '%s' to '%s' (%s)\n", val, fname, strerror(errno));
+		close(fd);
 		return -1;
 	}
+
+	close(fd);
 	return 0;
 }
 
@@ -523,7 +564,6 @@ int sysfs_set_num_signed(struct mdinfo *sra, struct mdinfo *dev,
 int sysfs_uevent(struct mdinfo *sra, char *event)
 {
 	char fname[MAX_SYSFS_PATH_LEN];
-	int n;
 	int fd;
 
 	snprintf(fname, MAX_SYSFS_PATH_LEN, "/sys/block/%s/uevent",
@@ -531,13 +571,14 @@ int sysfs_uevent(struct mdinfo *sra, char *event)
 	fd = open(fname, O_WRONLY);
 	if (fd < 0)
 		return -1;
-	n = write(fd, event, strlen(event));
-	close(fd);
-	if (n != (int)strlen(event)) {
-		dprintf("failed to write '%s' to '%s' (%s)\n",
-			event, fname, strerror(errno));
+
+	if (write_attr(event, fd)) {
+		pr_err("failed to write '%s' to '%s' (%s)\n", event, fname, strerror(errno));
+		close(fd);
 		return -1;
 	}
+
+	close(fd);
 	return 0;
 }
 
diff --git a/util.c b/util.c
index cc162278..2b660725 100644
--- a/util.c
+++ b/util.c
@@ -1854,13 +1854,22 @@ int hot_remove_disk(int mdfd, unsigned long dev, int force)
 int sys_hot_remove_disk(int statefd, int force)
 {
 	int cnt = force ? 500 : 5;
-	int ret;
+	static const char val[] = "faulty";
+
+	while (cnt--) {
+		int err = 0;
+		int ret = sysfs_write_descriptor(statefd, val, strlen(val), &err);
+
+		if (ret == MDADM_STATUS_SUCCESS)
+			return 0;
+
+		if (err != EBUSY)
+			break;
 
-	while ((ret = write(statefd, "remove", 6)) == -1 &&
-	       errno == EBUSY &&
-	       cnt-- > 0)
 		sleep_for(0, MSEC_TO_NSEC(10), true);
-	return ret == 6 ? 0 : -1;
+	}
+
+	return -1;
 }
 
 int set_array_info(int mdfd, struct supertype *st, struct mdinfo *info)