[PATCH] possible fix for broken floppy driver, take 2

Here is an updated patch for the floppy driver which got broken in
2.5.13. "read block 0 on ->revalidate()" is now implemented through
the bio interface, following a suggestion by Christoph Hellwig.

I still cannot explain why block_dev.c's ->bd_block_size change
caused data corruption, but removing that code fixes the floppy
driver and doesn't seem to cause any problems on my test box.

diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 3b3dd40bc69409c67f0b68b9d4485d38e5fe3a12..14864e69cc3a0fb187003ef0e92d98575ec8d39e 100644 (file)
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -243,6 +243,7 @@ static int irqdma_allocated;
 #include <linux/blk.h>
 #include <linux/blkpg.h>
 #include <linux/cdrom.h> /* for the compatibility eject ioctl */
+#include <linux/completion.h>
 
 #ifndef fd_get_dma_residue
 #define fd_get_dma_residue() get_dma_residue(FLOPPY_DMA)
@@ -3853,6 +3854,74 @@ static int check_floppy_change(kdev_t dev)
        return 0;
 }
 
+/*
+ * This implements "read block 0" for floppy_revalidate().
+ * Needed for format autodetection, checking whether there is
+ * a disk in the drive, and whether that disk is writable.
+ */
+
+static void floppy_rb0_complete(struct bio *bio)
+{
+       complete((struct completion*)bio->bi_private);
+}
+
+static int __floppy_read_block_0(struct block_device *bdev)
+{
+       struct bio bio;
+       struct bio_vec bio_vec;
+       struct completion complete;
+       struct page *page;
+       size_t size;
+
+       page = alloc_page(GFP_NOIO);
+       if (!page) {
+               process_fd_request();
+               return -ENOMEM;
+       }
+
+       size = bdev->bd_block_size;
+       if (!size)
+               size = 1024;
+
+       bio_init(&bio);
+       bio.bi_io_vec = &bio_vec;
+       bio_vec.bv_page = page;
+       bio_vec.bv_len = size;
+       bio_vec.bv_offset = 0;
+       bio.bi_vcnt = 1;
+       bio.bi_idx = 0;
+       bio.bi_size = size;
+       bio.bi_bdev = bdev;
+       bio.bi_sector = 0;
+       init_completion(&complete);
+       bio.bi_private = &complete;
+       bio.bi_end_io = floppy_rb0_complete;
+
+       submit_bio(READ, &bio);
+       run_task_queue(&tq_disk);
+       process_fd_request();
+       wait_for_completion(&complete);
+
+       __free_page(page);
+
+       return 0;
+}
+
+static int floppy_read_block_0(kdev_t dev)
+{
+       struct block_device *bdev;
+       int ret;
+
+       bdev = bdget(kdev_t_to_nr(dev));
+       if (!bdev) {
+               printk("No block device for %s\n", __bdevname(dev));
+               BUG();
+       }
+       ret = __floppy_read_block_0(bdev);
+       atomic_dec(&bdev->bd_count);
+       return ret;
+}
+
 /* revalidate the floppy disk, i.e. trigger format autodetection by reading
  * the bootblock (block 0). "Autodetection" is also needed to check whether
  * there is a disk in the drive at all... Thus we also do it for fixed
@@ -3860,9 +3929,6 @@ static int check_floppy_change(kdev_t dev)
 static int floppy_revalidate(kdev_t dev)
 {
 #define NO_GEOM (!current_type[drive] && !TYPE(dev))
-#if 0
-       struct buffer_head * bh;
-#endif
        int drive=DRIVE(dev);
        int cf;
 
@@ -3889,29 +3955,8 @@ static int floppy_revalidate(kdev_t dev)
                if (cf)
                        UDRS->generation++;
                if (NO_GEOM){
-#if 0
-       /*
-        * What the devil is going on here?  We are not guaranteed to do
-        * any IO and ENXIO case is nothing but ENOMEM in disguise - it
-        * happens if and only if buffer cache is out of memory.  WTF?
-        */
                        /* auto-sensing */
-                       int size = floppy_blocksizes[minor(dev)];
-                       if (!size)
-                               size = 1024;
-                       if (!(bh = getblk(dev,0,size))){
-                               process_fd_request();
-                               return -ENXIO;
-                       }
-                       if (bh && !buffer_uptodate(bh))
-                               ll_rw_block(READ, 1, &bh);
-                       process_fd_request();
-                       wait_on_buffer(bh);
-                       brelse(bh);
-                       return 0;
-#endif
-                       process_fd_request();
-                       return 0;
+                       return floppy_read_block_0(dev);
                }
                if (cf)
                        poll_drive(0, FD_RAW_NEED_DISK);

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 654d98a256b06b336f09753cb93960f7e5356893..27fd276f1a365dae7d72ccb37bd1aeb1ef6d8741 100644 (file)
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -606,16 +606,7 @@ static int do_open(struct block_device *bdev, struct inode *inode, struct file *
                        goto out2;
        }
        bdev->bd_inode->i_size = blkdev_size(dev);
-       if (!bdev->bd_openers) {
-               unsigned bsize = bdev_hardsect_size(bdev);
-               while (bsize < PAGE_CACHE_SIZE) {
-                       if (bdev->bd_inode->i_size & bsize)
-                               break;
-                       bsize <<= 1;
-               }
-               bdev->bd_block_size = bsize;
-               bdev->bd_inode->i_blkbits = blksize_bits(bsize);
-       }
+       bdev->bd_inode->i_blkbits = blksize_bits(block_size(bdev));
        bdev->bd_openers++;
        unlock_kernel();
        up(&bdev->bd_sem);