dump-in-use-buffers

   1 Add a ioctl which dumps out all of the in-use buffer heads for a block device
   2
   3 Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
   4 diff --git a/block/compat_ioctl.c b/block/compat_ioctl.c
   5 index 3d3e7a4..5c428a8 100644
   6 --- a/block/compat_ioctl.c
   7 +++ b/block/compat_ioctl.c
   8 @@ -705,6 +705,7 @@ long compat_blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg)
   9         switch (cmd) {
  10         case HDIO_GETGEO:
  11                 return compat_hdio_getgeo(disk, bdev, compat_ptr(arg));
  12 +       case BLKDUMPUSEDBUFFERS:
  13         case BLKFLSBUF:
  14         case BLKROSET:
  15         case BLKDISCARD:
  16 diff --git a/block/ioctl.c b/block/ioctl.c
  17 index c832d63..9b73953 100644
  18 --- a/block/ioctl.c
  19 +++ b/block/ioctl.c
  20 @@ -367,6 +367,13 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
  21                 ret = blk_trace_ioctl(bdev, cmd, (char __user *) arg);
  22                 unlock_kernel();
  23                 break;
  24 +       case BLKDUMPUSEDBUFFERS:
  25 +               if (!capable(CAP_SYS_ADMIN))
  26 +                       return -EACCES;
  27 +               dump_used_buffers(bdev);
  28 +               ret = 0;
  29 +               break;
  30 +
  31         default:
  32                 ret = __blkdev_driver_ioctl(bdev, mode, cmd, arg);
  33         }
  34 diff --git a/fs/buffer.c b/fs/buffer.c
  35 index 6569fda..852e7ac 100644
  36 --- a/fs/buffer.c
  37 +++ b/fs/buffer.c
  38 @@ -33,6 +33,7 @@
  39  #include <linux/writeback.h>
  40  #include <linux/hash.h>
  41  #include <linux/suspend.h>
  42 +#include <linux/pagevec.h>
  43  #include <linux/buffer_head.h>
  44  #include <linux/task_io_accounting_ops.h>
  45  #include <linux/bio.h>
  46 @@ -246,6 +247,45 @@ void thaw_bdev(struct block_device *bdev, struct super_block *sb)
  47  }
  48  EXPORT_SYMBOL(thaw_bdev);
  49
  50 +void dump_used_buffers(struct block_device *bdev)
  51 +{
  52 +       struct inode *bd_inode = bdev->bd_inode;
  53 +       struct address_space *bd_mapping = bd_inode->i_mapping;
  54 +       struct buffer_head *bh, *head;
  55 +       struct pagevec pvec;
  56 +       unsigned long index = 0;
  57 +       int nr_pages, i, count, total = 0;
  58 +       char b[BDEVNAME_SIZE];
  59 +
  60 +       spin_lock(&bd_mapping->private_lock);
  61 +       printk(KERN_INFO "Begin dump of block device %s\n", bdevname(bdev, b));
  62 +       while (1) {
  63 +               nr_pages = pagevec_lookup(&pvec, bd_mapping, index, PAGEVEC_SIZE);
  64 +               if (nr_pages == 0)
  65 +                       break;
  66 +               for (i = 0; i < nr_pages; i++) {
  67 +                       struct page *page = pvec.pages[i];
  68 +                       index = page->index + 1;
  69 +
  70 +                       if (!page_has_buffers(page))
  71 +                               continue;
  72 +                       bh = head = page_buffers(page);
  73 +                       do {
  74 +                               count = atomic_read(&bh->b_count);
  75 +                               if (count) {
  76 +                                       printk(KERN_INFO
  77 +                                              "buffer in-use: block %Lu count %d\n",
  78 +                                              (unsigned long long) bh->b_blocknr, count);
  79 +                                       total++;
  80 +                               }
  81 +                               bh = bh->b_this_page;
  82 +                       } while (bh != head);
  83 +               }
  84 +       }
  85 +       printk(KERN_INFO "Total number of in-use buffers: %d\n", total);
  86 +       spin_unlock(&bd_mapping->private_lock);
  87 +}
  88 +
  89  /*
  90   * Various filesystems appear to want __find_get_block to be non-blocking.
  91   * But it's the page lock which protects the buffers.  To get around this,
  92 diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
  93 index 3ce64b9..053e644 100644
  94 --- a/include/linux/buffer_head.h
  95 +++ b/include/linux/buffer_head.h
  96 @@ -193,6 +193,7 @@ void write_boundary_block(struct block_device *bdev,
  97                         sector_t bblock, unsigned blocksize);
  98  int bh_uptodate_or_lock(struct buffer_head *bh);
  99  int bh_submit_read(struct buffer_head *bh);
 100 +void dump_used_buffers(struct block_device *bdev);
 101
 102  extern int buffer_heads_over_limit;
 103
 104 diff --git a/include/linux/fs.h b/include/linux/fs.h
 105 index 5b248d6..a08e4d0 100644
 106 --- a/include/linux/fs.h
 107 +++ b/include/linux/fs.h
 108 @@ -231,6 +231,8 @@ extern int dir_notify_enable;
 109  #define BLKTRACETEARDOWN _IO(0x12,118)
 110  #define BLKDISCARD _IO(0x12,119)
 111
 112 +#define BLKDUMPUSEDBUFFERS _IO(0x12,130)
 113 +
 114  #define BMAP_IOCTL 1           /* obsolete - kept for compatibility */
 115  #define FIBMAP    _IO(0x00,1)  /* bmap access */
 116  #define FIGETBSZ   _IO(0x00,2) /* get the block size used for bmap */