btrfs-progs: check return of posix_fadvise

It seems highly unlikely that posix_fadvise could fail,
and even if it does, it was only advisory.  Still, if
it does, we could issue a notice to the user.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>

2 files changed, 6 insertions, 3 deletions

diff --git a/disk-io.c b/disk-io.c
index 897d0cf0..97fbfbd5 100644
--- a/disk-io.c
+++ b/disk-io.c
@@ -822,7 +822,8 @@ static struct btrfs_fs_info *__open_ctree_fd(int fp, const char *path,
 		sb_bytenr = BTRFS_SUPER_INFO_OFFSET;
 
 	/* try to drop all the caches */
-	posix_fadvise(fp, 0, 0, POSIX_FADV_DONTNEED);
+	if (posix_fadvise(fp, 0, 0, POSIX_FADV_DONTNEED))
+		fprintf(stderr, "Warning, could not drop caches\n");
 
 	ret = btrfs_scan_one_device(fp, path, &fs_devices,
 				    &total_devs, sb_bytenr);
@@ -1282,7 +1283,8 @@ static int close_all_devices(struct btrfs_fs_info *fs_info)
 		device = list_entry(next, struct btrfs_device, dev_list);
 		if (device->fd) {
 			fsync(device->fd);
-			posix_fadvise(device->fd, 0, 0, POSIX_FADV_DONTNEED);
+			if (posix_fadvise(device->fd, 0, 0, POSIX_FADV_DONTNEED))
+				fprintf(stderr, "Warning, could not drop caches\n");
 		}
 		close(device->fd);
 	}
diff --git a/volumes.c b/volumes.c
index ca1b4025..c0d02d13 100644
--- a/volumes.c
+++ b/volumes.c
@@ -193,7 +193,8 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices, int flags)
 			goto fail;
 		}
 
-		posix_fadvise(fd, 0, 0, POSIX_FADV_DONTNEED);
+		if (posix_fadvise(fd, 0, 0, POSIX_FADV_DONTNEED))
+			fprintf(stderr, "Warning, could not drop caches\n");
 
 		if (device->devid == fs_devices->latest_devid)
 			fs_devices->latest_bdev = fd;