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authorJosef Bacik <jbacik@redhat.com>2008-10-03 17:32:43 -0400
committerTheodore Ts'o <tytso@mit.edu>2008-10-03 17:32:43 -0400
commit68c9d702bb72f367f3b148963ec6cf5e07ff7f65 (patch)
tree16fc61a1bd973c14a7858ab1fbcb306d3ae75184 /fs/ioctl.c
parent00dc417fa3e763345b34ccb6034d72de76eea0a1 (diff)
generic block based fiemap implementation
Any block based fs (this patch includes ext3) just has to declare its own fiemap() function and then call this generic function with its own get_block_t. This works well for block based filesystems that will map multiple contiguous blocks at one time, but will work for filesystems that only map one block at a time, you will just end up with an "extent" for each block. One gotcha is this will not play nicely where there is hole+data after the EOF. This function will assume its hit the end of the data as soon as it hits a hole after the EOF, so if there is any data past that it will not pick that up. AFAIK no block based fs does this anyway, but its in the comments of the function anyway just in case. Signed-off-by: Josef Bacik <jbacik@redhat.com> Signed-off-by: Mark Fasheh <mfasheh@suse.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Cc: linux-fsdevel@vger.kernel.org
Diffstat (limited to 'fs/ioctl.c')
-rw-r--r--fs/ioctl.c118
1 files changed, 118 insertions, 0 deletions
diff --git a/fs/ioctl.c b/fs/ioctl.c
index 045d9601fbb..33a6b7ecb8b 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -13,6 +13,8 @@
#include <linux/security.h>
#include <linux/module.h>
#include <linux/uaccess.h>
+#include <linux/writeback.h>
+#include <linux/buffer_head.h>
#include <asm/ioctls.h>
@@ -224,6 +226,122 @@ static int ioctl_fiemap(struct file *filp, unsigned long arg)
return error;
}
+#define blk_to_logical(inode, blk) (blk << (inode)->i_blkbits)
+#define logical_to_blk(inode, offset) (offset >> (inode)->i_blkbits);
+
+/*
+ * @inode - the inode to map
+ * @arg - the pointer to userspace where we copy everything to
+ * @get_block - the fs's get_block function
+ *
+ * This does FIEMAP for block based inodes. Basically it will just loop
+ * through get_block until we hit the number of extents we want to map, or we
+ * go past the end of the file and hit a hole.
+ *
+ * If it is possible to have data blocks beyond a hole past @inode->i_size, then
+ * please do not use this function, it will stop at the first unmapped block
+ * beyond i_size
+ */
+int generic_block_fiemap(struct inode *inode,
+ struct fiemap_extent_info *fieinfo, u64 start,
+ u64 len, get_block_t *get_block)
+{
+ struct buffer_head tmp;
+ unsigned int start_blk;
+ long long length = 0, map_len = 0;
+ u64 logical = 0, phys = 0, size = 0;
+ u32 flags = FIEMAP_EXTENT_MERGED;
+ int ret = 0;
+
+ if ((ret = fiemap_check_flags(fieinfo, FIEMAP_FLAG_SYNC)))
+ return ret;
+
+ start_blk = logical_to_blk(inode, start);
+
+ /* guard against change */
+ mutex_lock(&inode->i_mutex);
+
+ length = (long long)min_t(u64, len, i_size_read(inode));
+ map_len = length;
+
+ do {
+ /*
+ * we set b_size to the total size we want so it will map as
+ * many contiguous blocks as possible at once
+ */
+ memset(&tmp, 0, sizeof(struct buffer_head));
+ tmp.b_size = map_len;
+
+ ret = get_block(inode, start_blk, &tmp, 0);
+ if (ret)
+ break;
+
+ /* HOLE */
+ if (!buffer_mapped(&tmp)) {
+ /*
+ * first hole after going past the EOF, this is our
+ * last extent
+ */
+ if (length <= 0) {
+ flags = FIEMAP_EXTENT_MERGED|FIEMAP_EXTENT_LAST;
+ ret = fiemap_fill_next_extent(fieinfo, logical,
+ phys, size,
+ flags);
+ break;
+ }
+
+ length -= blk_to_logical(inode, 1);
+
+ /* if we have holes up to/past EOF then we're done */
+ if (length <= 0)
+ break;
+
+ start_blk++;
+ } else {
+ if (length <= 0 && size) {
+ ret = fiemap_fill_next_extent(fieinfo, logical,
+ phys, size,
+ flags);
+ if (ret)
+ break;
+ }
+
+ logical = blk_to_logical(inode, start_blk);
+ phys = blk_to_logical(inode, tmp.b_blocknr);
+ size = tmp.b_size;
+ flags = FIEMAP_EXTENT_MERGED;
+
+ length -= tmp.b_size;
+ start_blk += logical_to_blk(inode, size);
+
+ /*
+ * if we are past the EOF we need to loop again to see
+ * if there is a hole so we can mark this extent as the
+ * last one, and if not keep mapping things until we
+ * find a hole, or we run out of slots in the extent
+ * array
+ */
+ if (length <= 0)
+ continue;
+
+ ret = fiemap_fill_next_extent(fieinfo, logical, phys,
+ size, flags);
+ if (ret)
+ break;
+ }
+ cond_resched();
+ } while (1);
+
+ mutex_unlock(&inode->i_mutex);
+
+ /* if ret is 1 then we just hit the end of the extent array */
+ if (ret == 1)
+ ret = 0;
+
+ return ret;
+}
+EXPORT_SYMBOL(generic_block_fiemap);
+
static int file_ioctl(struct file *filp, unsigned int cmd,
unsigned long arg)
{