Balance filter to take only chunks which have (or had) a stripe on the
given device. Useful if a device has been forcibly removed from the
filesystem, and the data from that device needs rebuilding.

Signed-off-by: Hugo Mills <h...@carfax.org.uk>
---
 fs/btrfs/ioctl.h   |    8 ++++++--
 fs/btrfs/volumes.c |   16 +++++++++++++++-
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
index eb91d20..54523c0 100644
--- a/fs/btrfs/ioctl.h
+++ b/fs/btrfs/ioctl.h
@@ -166,7 +166,8 @@ struct btrfs_ioctl_balance_progress {
 #define BTRFS_BALANCE_FILTER_COUNT_ONLY (1 << 0)
 
 #define BTRFS_BALANCE_FILTER_CHUNK_TYPE (1 << 1)
-#define BTRFS_BALANCE_FILTER_MASK ((1 << 2) - 1) /* Logical or of all filter
+#define BTRFS_BALANCE_FILTER_DEVID (1 << 2)
+#define BTRFS_BALANCE_FILTER_MASK ((1 << 3) - 1) /* Logical or of all filter
                                       * flags -- effectively versions
                                       * the filtered balance ioctl */
 
@@ -183,7 +184,10 @@ struct btrfs_ioctl_balance_start {
        __u64 chunk_type;      /* Flag bits required */
        __u64 chunk_type_mask; /* Mask of bits to examine */
 
-       __u64 spare[506]; /* Make up the size of the structure to 4088
+       /* For FILTER_DEVID */
+       __u64 devid;
+
+       __u64 spare[505]; /* Make up the size of the structure to 4088
                           * bytes for future expansion */
 };
 
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 95c603a..e7fa2ab 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2036,6 +2036,7 @@ int balance_chunk_filter(struct btrfs_ioctl_balance_start 
*filter,
 {
        struct extent_buffer *eb;
        struct btrfs_chunk *chunk;
+       int i;
 
        /* No filter defined, everything matches */
        if (!filter)
@@ -2056,8 +2057,21 @@ int balance_chunk_filter(struct 
btrfs_ioctl_balance_start *filter,
                        return 0;
                }
        }
+       if (filter->flags & BTRFS_BALANCE_FILTER_DEVID) {
+               int num_stripes = btrfs_chunk_num_stripes(eb, chunk);
+               int res = 0;
+               for (i = 0; i < num_stripes; i++) {
+                       struct btrfs_stripe *stripe = btrfs_stripe_nr(chunk, i);
+                       if (btrfs_stripe_devid(eb, stripe) == filter->devid) {
+                               res = 1;
+                               break;
+                       }
+               }
+               if (!res)
+                       return 0;
+       }
 
-       return ret;
+       return 1;
 }
 
 /* Define a type, and two functions which can be used for the two
-- 
1.7.2.5

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