* [PATCH v2] Btrfs: export btrfs space shared info to userspace
@ 2013-09-16 8:18 Liu Bo
2013-09-16 8:55 ` David Sterba
0 siblings, 1 reply; 3+ messages in thread
From: Liu Bo @ 2013-09-16 8:18 UTC (permalink / raw)
To: linux-btrfs; +Cc: dsterba, jeff.liu
Similar to ocfs2, btrfs also supports that extents can be shared by
different inodes, and there are some userspace tools requesting
for this kind of 'space shared infomation'.[1]
ocfs2 uses flag FIEMAP_EXTENT_SHARED, so does btrfs.
[1]: http://thr3ads.net/ocfs2-devel/2010/09/489052-PATCH-3-3-shared-du-using-fiemap-to-figure-up-the-shared-extents-per-file-and-the-footprint-in
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
---
v2: use 'unsigned long' instead of 'int'.
fs/btrfs/extent_io.c | 34 +++++++++++++++++++++++++++++++++-
1 files changed, 33 insertions(+), 1 deletions(-)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 09582b8..a097441 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -20,6 +20,7 @@
#include "check-integrity.h"
#include "locking.h"
#include "rcu-string.h"
+#include "backref.h"
static struct kmem_cache *extent_state_cache;
static struct kmem_cache *extent_buffer_cache;
@@ -4056,6 +4057,19 @@ static struct extent_map *get_extent_skip_holes(struct inode *inode,
return NULL;
}
+static noinline int count_ext_ref(u64 inum, u64 offset, u64 root_id, void *ctx)
+{
+ unsigned long cnt = *((unsigned long *)ctx);
+
+ cnt++;
+ *((unsigned long *)ctx) = cnt;
+
+ /* Now we're sure that the extent is shared. */
+ if (cnt > 1)
+ return 1;
+ return 0;
+}
+
int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
__u64 start, __u64 len, get_extent_t *get_extent)
{
@@ -4122,7 +4136,7 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
last = found_key.offset;
last_for_get_extent = last + 1;
}
- btrfs_free_path(path);
+ btrfs_release_path(path);
/*
* we might have some extents allocated but more delalloc past those
@@ -4192,7 +4206,24 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
flags |= (FIEMAP_EXTENT_DELALLOC |
FIEMAP_EXTENT_UNKNOWN);
} else {
+ unsigned long ref_cnt = 0;
+
disko = em->block_start + offset_in_extent;
+
+ /*
+ * As btrfs supports shared space, this information
+ * can be exported to userspace tools via
+ * flag FIEMAP_EXTENT_SHARED.
+ */
+ ret = iterate_inodes_from_logical(
+ em->block_start,
+ BTRFS_I(inode)->root->fs_info,
+ path, count_ext_ref, &ref_cnt);
+ if (ret < 0)
+ goto out_free;
+
+ if (ref_cnt > 1)
+ flags |= FIEMAP_EXTENT_SHARED;
}
if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags))
flags |= FIEMAP_EXTENT_ENCODED;
@@ -4226,6 +4257,7 @@ out_free:
out:
unlock_extent_cached(&BTRFS_I(inode)->io_tree, start, start + len - 1,
&cached_state, GFP_NOFS);
+ btrfs_free_path(path);
return ret;
}
--
1.7.7
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] Btrfs: export btrfs space shared info to userspace
2013-09-16 8:18 [PATCH v2] Btrfs: export btrfs space shared info to userspace Liu Bo
@ 2013-09-16 8:55 ` David Sterba
2013-09-16 9:28 ` Liu Bo
0 siblings, 1 reply; 3+ messages in thread
From: David Sterba @ 2013-09-16 8:55 UTC (permalink / raw)
To: Liu Bo; +Cc: linux-btrfs, jeff.liu
On Mon, Sep 16, 2013 at 04:18:24PM +0800, Liu Bo wrote:
> @@ -4122,7 +4136,7 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> last = found_key.offset;
> last_for_get_extent = last + 1;
> }
> - btrfs_free_path(path);
> + btrfs_release_path(path);
>
> /*
> * we might have some extents allocated but more delalloc past those
> @@ -4192,7 +4206,24 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> flags |= (FIEMAP_EXTENT_DELALLOC |
> FIEMAP_EXTENT_UNKNOWN);
> } else {
> + unsigned long ref_cnt = 0;
> +
> disko = em->block_start + offset_in_extent;
> +
> + /*
> + * As btrfs supports shared space, this information
> + * can be exported to userspace tools via
> + * flag FIEMAP_EXTENT_SHARED.
> + */
> + ret = iterate_inodes_from_logical(
> + em->block_start,
> + BTRFS_I(inode)->root->fs_info,
> + path, count_ext_ref, &ref_cnt);
> + if (ret < 0)
> + goto out_free;
> +
> + if (ref_cnt > 1)
> + flags |= FIEMAP_EXTENT_SHARED;
> }
> if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags))
> flags |= FIEMAP_EXTENT_ENCODED;
> @@ -4226,6 +4257,7 @@ out_free:
> out:
> unlock_extent_cached(&BTRFS_I(inode)->io_tree, start, start + len - 1,
> &cached_state, GFP_NOFS);
> + btrfs_free_path(path);
I think this free_path should go before unlock_extent_cached, it's not
needed for unlock_extent_cached itself and will delay unlocking the
path unnecessarily (it's set to leave_spinning = 1).
> return ret;
> }
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] Btrfs: export btrfs space shared info to userspace
2013-09-16 8:55 ` David Sterba
@ 2013-09-16 9:28 ` Liu Bo
0 siblings, 0 replies; 3+ messages in thread
From: Liu Bo @ 2013-09-16 9:28 UTC (permalink / raw)
To: dsterba, linux-btrfs, jeff.liu
On Mon, Sep 16, 2013 at 10:55:17AM +0200, David Sterba wrote:
> On Mon, Sep 16, 2013 at 04:18:24PM +0800, Liu Bo wrote:
> > @@ -4122,7 +4136,7 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> > last = found_key.offset;
> > last_for_get_extent = last + 1;
> > }
> > - btrfs_free_path(path);
> > + btrfs_release_path(path);
> >
> > /*
> > * we might have some extents allocated but more delalloc past those
> > @@ -4192,7 +4206,24 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> > flags |= (FIEMAP_EXTENT_DELALLOC |
> > FIEMAP_EXTENT_UNKNOWN);
> > } else {
> > + unsigned long ref_cnt = 0;
> > +
> > disko = em->block_start + offset_in_extent;
> > +
> > + /*
> > + * As btrfs supports shared space, this information
> > + * can be exported to userspace tools via
> > + * flag FIEMAP_EXTENT_SHARED.
> > + */
> > + ret = iterate_inodes_from_logical(
> > + em->block_start,
> > + BTRFS_I(inode)->root->fs_info,
> > + path, count_ext_ref, &ref_cnt);
> > + if (ret < 0)
> > + goto out_free;
> > +
> > + if (ref_cnt > 1)
> > + flags |= FIEMAP_EXTENT_SHARED;
> > }
> > if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags))
> > flags |= FIEMAP_EXTENT_ENCODED;
> > @@ -4226,6 +4257,7 @@ out_free:
> > out:
> > unlock_extent_cached(&BTRFS_I(inode)->io_tree, start, start + len - 1,
> > &cached_state, GFP_NOFS);
> > + btrfs_free_path(path);
>
> I think this free_path should go before unlock_extent_cached, it's not
> needed for unlock_extent_cached itself and will delay unlocking the
> path unnecessarily (it's set to leave_spinning = 1).
Path has been released and unlocked inside iterate_inodes_from_logical() though.
But yeah, path is unrelevant with unlock_extent_cached(), it can be done
earlier.
-liubo
>
> > return ret;
> > }
^ permalink raw reply [flat|nested] 3+ messages in thread
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2013-09-16 8:55 ` David Sterba
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