Returns a file's size on disk. Based on a patch by Chris Ball, improved
following suggestions by Chris Mason and Miao Xie.
Minimal example:
#include <sys/ioctl.h>
#include <fcntl.h>
#include <stdint.h>
#include <stdio.h>
#define BTRFS_IOCTL_MAGIC 0x94
#define BTRFS_IOC_COMPR_SIZE _IOR(BTRFS_IOCTL_MAGIC, 21, uint64_t)
int main(int argc, char **argv)
{
uint64_t size = -1;
int d = open(argv[1], O_RDONLY);
ioctl(d, BTRFS_IOC_COMPR_SIZE, &size);
printf("%zd\n", size);
return 0;
}
Signed-off-by: Ulrich Hecht <u...@suse.de>
---
fs/btrfs/ioctl.c | 41 +++++++++++++++++++++++++++++++++++++++++
fs/btrfs/ioctl.h | 1 +
2 files changed, 42 insertions(+), 0 deletions(-)
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 9254b3d..29651c9 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1750,6 +1750,45 @@ out_drop_write:
return ret;
}
+static long btrfs_ioctl_compsize(struct file *file, void __user *argp)
+{
+ /* This ioctl returns the compressed size of an inode on disk
+ * by counting the on-disk space used by all of its extents.
+ */
+ struct inode *inode = fdentry(file)->d_inode;
+ struct extent_map *em;
+ u64 len = inode->i_size;
+ u64 compressed_size = 0;
+ u64 offset = 0;
+
+ if (S_ISDIR(inode->i_mode))
+ return -EISDIR;
+
+ mutex_lock(&inode->i_mutex);
+
+ /* do any pending delalloc/csum calc on inode, one way or
+ another, and lock file content */
+ btrfs_wait_ordered_range(inode, 0, (u64)-1);
+
+ while (offset < len) {
+ em = btrfs_get_extent(inode, NULL, 0, offset, 1, 0);
+ BUG_ON(IS_ERR(em) || !em);
+ if (em->block_len != (u64)-1)
+ compressed_size += em->block_len;
+ offset += em->len;
+ free_extent_map(em);
+ }
+ mutex_unlock(&inode->i_mutex);
+
+ unlock_extent(&BTRFS_I(inode)->io_tree, 0, len, GFP_NOFS);
+
+ /* We've succeeded in going through all extents; set the final size. */
+ if (copy_to_user(argp, &compressed_size, sizeof(compressed_size)))
+ return -EFAULT;
+ else
+ return 0;
+}
+
static long btrfs_ioctl_clone_range(struct file *file, void __user *argp)
{
struct btrfs_ioctl_clone_range_args args;
@@ -2034,6 +2073,8 @@ long btrfs_ioctl(struct file *file, unsigned int
case BTRFS_IOC_SYNC:
btrfs_sync_fs(file->f_dentry->d_sb, 1);
return 0;
+ case BTRFS_IOC_COMPR_SIZE:
+ return btrfs_ioctl_compsize(file, argp);
}
return -ENOTTY;
diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
index 424694a..a01ef1e 100644
--- a/fs/btrfs/ioctl.h
+++ b/fs/btrfs/ioctl.h
@@ -178,4 +178,5 @@ struct btrfs_ioctl_space_args {
#define BTRFS_IOC_DEFAULT_SUBVOL _IOW(BTRFS_IOCTL_MAGIC, 19, u64)
#define BTRFS_IOC_SPACE_INFO _IOWR(BTRFS_IOCTL_MAGIC, 20, \
struct btrfs_ioctl_space_args)
+#define BTRFS_IOC_COMPR_SIZE _IOR(BTRFS_IOCTL_MAGIC, 21, u64)
#endif
--
1.7.1
--
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