floppy: bail out in open() if drive is not responding to block0 read

commit 7b7b68bba5ef23734c35ffb0d8d82079ed604d33 upstream.

In case reading of block 0 during open() fails, it is not the right thing
to let open() succeed.

Fix this by introducing FD_OPEN_SHOULD_FAIL_BIT flag, and setting it in
case the bio callback encounters an error while trying to read block 0.

As a bonus, this works around certain broken userspace (blkid), which is
not able to properly handle read()s returning IO errors. Hence be nice to
those, and bail out during open() already; if block 0 is not readable,
read()s are not going to provide any meaningful data anyway.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 04ceb7e..690011d 100644 (file)
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -3691,9 +3691,12 @@ static int floppy_open(struct block_device *bdev, fmode_t mode)
        if (!(mode & FMODE_NDELAY)) {
                if (mode & (FMODE_READ|FMODE_WRITE)) {
                        UDRS->last_checked = 0;
+                       clear_bit(FD_OPEN_SHOULD_FAIL_BIT, &UDRS->flags);
                        check_disk_change(bdev);
                        if (test_bit(FD_DISK_CHANGED_BIT, &UDRS->flags))
                                goto out;
+                       if (test_bit(FD_OPEN_SHOULD_FAIL_BIT, &UDRS->flags))
+                               goto out;
                }
                res = -EROFS;
                if ((mode & FMODE_WRITE) &&
@@ -3746,17 +3749,29 @@ static unsigned int floppy_check_events(struct gendisk *disk,
  * a disk in the drive, and whether that disk is writable.
  */
 
-static void floppy_rb0_complete(struct bio *bio, int err)
+struct rb0_cbdata {
+       int drive;
+       struct completion complete;
+};
+
+static void floppy_rb0_cb(struct bio *bio, int err)
 {
-       complete((struct completion *)bio->bi_private);
+       struct rb0_cbdata *cbdata = (struct rb0_cbdata *)bio->bi_private;
+       int drive = cbdata->drive;
+
+       if (err) {
+               pr_info("floppy: error %d while reading block 0", err);
+               set_bit(FD_OPEN_SHOULD_FAIL_BIT, &UDRS->flags);
+       }
+       complete(&cbdata->complete);
 }
 
-static int __floppy_read_block_0(struct block_device *bdev)
+static int __floppy_read_block_0(struct block_device *bdev, int drive)
 {
        struct bio bio;
        struct bio_vec bio_vec;
-       struct completion complete;
        struct page *page;
+       struct rb0_cbdata cbdata;
        size_t size;
 
        page = alloc_page(GFP_NOIO);
@@ -3769,6 +3784,8 @@ static int __floppy_read_block_0(struct block_device *bdev)
        if (!size)
                size = 1024;
 
+       cbdata.drive = drive;
+
        bio_init(&bio);
        bio.bi_io_vec = &bio_vec;
        bio_vec.bv_page = page;
@@ -3779,13 +3796,14 @@ static int __floppy_read_block_0(struct block_device *bdev)
        bio.bi_bdev = bdev;
        bio.bi_sector = 0;
        bio.bi_flags = (1 << BIO_QUIET);
-       init_completion(&complete);
-       bio.bi_private = &complete;
-       bio.bi_end_io = floppy_rb0_complete;
+       bio.bi_private = &cbdata;
+       bio.bi_end_io = floppy_rb0_cb;
 
        submit_bio(READ, &bio);
        process_fd_request();
-       wait_for_completion(&complete);
+
+       init_completion(&cbdata.complete);
+       wait_for_completion(&cbdata.complete);
 
        __free_page(page);
 
@@ -3827,7 +3845,7 @@ static int floppy_revalidate(struct gendisk *disk)
                        UDRS->generation++;
                if (drive_no_geom(drive)) {
                        /* auto-sensing */
-                       res = __floppy_read_block_0(opened_bdev[drive]);
+                       res = __floppy_read_block_0(opened_bdev[drive], drive);
                } else {
                        if (cf)
                                poll_drive(false, FD_RAW_NEED_DISK);

diff --git a/include/uapi/linux/fd.h b/include/uapi/linux/fd.h
index f1f3dd5..84c517c 100644 (file)
--- a/include/uapi/linux/fd.h
+++ b/include/uapi/linux/fd.h
@@ -185,7 +185,8 @@ enum {
                                 * to clear media change status */
        FD_UNUSED_BIT,
        FD_DISK_CHANGED_BIT,    /* disk has been changed since last i/o */
-       FD_DISK_WRITABLE_BIT    /* disk is writable */
+       FD_DISK_WRITABLE_BIT,   /* disk is writable */
+       FD_OPEN_SHOULD_FAIL_BIT
 };
 
 #define FDSETDRVPRM _IOW(2, 0x90, struct floppy_drive_params)