[PATCH 091/119] xfs: add dedupe range vfs function

Darrick J. Wong
2016-06-17T01:27:46Z

Define a VFS function which allows userspace to request that the
kernel reflink a range of blocks between two files if the ranges'
contents match. The function fits the new VFS ioctl that standardizes
the checking for the btrfs EXTENT SAME ioctl.

v2: Plug into the VFS function pointers instead of handling ioctls
directly, and lock the pages so they don't disappear while we're
trying to compare them.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
fs/xfs/libxfs/xfs_fs.h | 30 +++++++++++
fs/xfs/xfs_file.c | 48 +++++++++++++++++-
fs/xfs/xfs_reflink.c | 127 ++++++++++++++++++++++++++++++++++++++++++++++++
fs/xfs/xfs_reflink.h | 5 ++
4 files changed, 204 insertions(+), 6 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
index 788e006..6230230 100644
--- a/fs/xfs/libxfs/xfs_fs.h
+++ b/fs/xfs/libxfs/xfs_fs.h
@@ -542,8 +542,38 @@ struct xfs_clone_args {
__u64 dest_offset;
};

+/* extent-same (dedupe) ioctls; these MUST match the btrfs ioctl definitions */
+#define XFS_EXTENT_DATA_SAME 0
+#define XFS_EXTENT_DATA_DIFFERS 1
+
+/* from struct btrfs_ioctl_file_extent_same_info */
+struct xfs_extent_data_info {
+ __s64 fd; /* in - destination file */
+ __u64 logical_offset; /* in - start of extent in destination */
+ __u64 bytes_deduped; /* out - total # of bytes we were able
+ * to dedupe from this file */
+ /* status of this dedupe operation:
+ * < 0 for error
+ * == XFS_EXTENT_DATA_SAME if dedupe succeeds
+ * == XFS_EXTENT_DATA_DIFFERS if data differs
+ */
+ __s32 status; /* out - see above description */
+ __u32 reserved;
+};
+
+/* from struct btrfs_ioctl_file_extent_same_args */
+struct xfs_extent_data {
+ __u64 logical_offset; /* in - start of extent in source */
+ __u64 length; /* in - length of extent */
+ __u16 dest_count; /* in - total elements in info array */
+ __u16 reserved1;
+ __u32 reserved2;
+ struct xfs_extent_data_info info[0];
+};
+
#define XFS_IOC_CLONE _IOW (0x94, 9, int)
#define XFS_IOC_CLONE_RANGE _IOW (0x94, 13, struct xfs_clone_args)
+#define XFS_IOC_FILE_EXTENT_SAME _IOWR(0x94, 54, struct xfs_extent_data)

#ifndef HAVE_BBMACROS
/*
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index c2953bd..02e9139 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -1083,7 +1083,8 @@ xfs_file_share_range(
loff_t pos_in,
struct file *file_out,
loff_t pos_out,
- u64 len)
+ u64 len,
+ bool is_dedupe)
{
struct inode *inode_in;
struct inode *inode_out;
@@ -1092,6 +1093,7 @@ xfs_file_share_range(
loff_t isize;
int same_inode;
loff_t blen;
+ unsigned int flags = 0;

inode_in = file_inode(file_in);
inode_out = file_inode(file_out);
@@ -1129,6 +1131,15 @@ xfs_file_share_range(
pos_in + len > isize)
return -EINVAL;

+ /* Don't allow dedupe past EOF in the dest file */
+ if (is_dedupe) {
+ loff_t disize;
+
+ disize = i_size_read(inode_out);
+ if (pos_out >= disize || pos_out + len > disize)
+ return -EINVAL;
+ }
+
/* If we're linking to EOF, continue to the block boundary. */
if (pos_in + len == isize)
blen = ALIGN(isize, bs) - pos_in;
@@ -1152,8 +1163,10 @@ xfs_file_share_range(
if (ret)
goto out_unlock;

+ if (is_dedupe)
+ flags |= XFS_REFLINK_DEDUPE;
ret = xfs_reflink_remap_range(XFS_I(inode_in), pos_in, XFS_I(inode_out),
- pos_out, len);
+ pos_out, len, flags);
if (ret < 0)
goto out_unlock;

@@ -1173,7 +1186,7 @@ xfs_file_copy_range(
int error;

error = xfs_file_share_range(file_in, pos_in, file_out, pos_out,
- len);
+ len, false);
if (error)
return error;
return len;
@@ -1188,7 +1201,33 @@ xfs_file_clone_range(
u64 len)
{
return xfs_file_share_range(file_in, pos_in, file_out, pos_out,
- len);
+ len, false);
+}
+
+#define XFS_MAX_DEDUPE_LEN (16 * 1024 * 1024)
+STATIC ssize_t
+xfs_file_dedupe_range(
+ struct file *src_file,
+ u64 loff,
+ u64 len,
+ struct file *dst_file,
+ u64 dst_loff)
+{
+ int error;
+
+ /*
+ * Limit the total length we will dedupe for each operation.
+ * This is intended to bound the total time spent in this
+ * ioctl to something sane.
+ */
+ if (len > XFS_MAX_DEDUPE_LEN)
+ len = XFS_MAX_DEDUPE_LEN;
+
+ error = xfs_file_share_range(src_file, loff, dst_file, dst_loff,
+ len, true);
+ if (error)
+ return error;
+ return len;
}

STATIC int
@@ -1861,6 +1900,7 @@ const struct file_operations xfs_file_operations = {
.fallocate = xfs_file_fallocate,
.copy_file_range = xfs_file_copy_range,
.clone_file_range = xfs_file_clone_range,
+ .dedupe_file_range = xfs_file_dedupe_range,
};

const struct file_operations xfs_dir_file_operations = {
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index c01c0c7..c42a6e1 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1231,6 +1231,111 @@ err:
}

/*
+ * Read a page's worth of file data into the page cache. Return the page
+ * locked.
+ */
+static struct page *
+xfs_get_page(
+ struct inode *inode,
+ xfs_off_t offset)
+{
+ struct address_space *mapping;
+ struct page *page;
+ pgoff_t n;
+
+ n = offset >> PAGE_SHIFT;
+ mapping = inode->i_mapping;
+ page = read_mapping_page(mapping, n, NULL);
+ if (IS_ERR(page))
+ return page;
+ if (!PageUptodate(page)) {
+ put_page(page);
+ return ERR_PTR(-EIO);
+ }
+ lock_page(page);
+ return page;
+}
+
+/*
+ * Compare extents of two files to see if they are the same.
+ */
+static int
+xfs_compare_extents(
+ struct inode *src,
+ xfs_off_t srcoff,
+ struct inode *dest,
+ xfs_off_t destoff,
+ xfs_off_t len,
+ bool *is_same)
+{
+ xfs_off_t src_poff;
+ xfs_off_t dest_poff;
+ void *src_addr;
+ void *dest_addr;
+ struct page *src_page;
+ struct page *dest_page;
+ xfs_off_t cmp_len;
+ bool same;
+ int error;
+
+ error = -EINVAL;
+ same = true;
+ while (len) {
+ src_poff = srcoff & (PAGE_SIZE - 1);
+ dest_poff = destoff & (PAGE_SIZE - 1);
+ cmp_len = min(PAGE_SIZE - src_poff,
+ PAGE_SIZE - dest_poff);
+ cmp_len = min(cmp_len, len);
+ ASSERT(cmp_len > 0);
+
+ trace_xfs_reflink_compare_extents(XFS_I(src), srcoff, cmp_len,
+ XFS_I(dest), destoff);
+
+ src_page = xfs_get_page(src, srcoff);
+ if (IS_ERR(src_page)) {
+ error = PTR_ERR(src_page);
+ goto out_error;
+ }
+ dest_page = xfs_get_page(dest, destoff);
+ if (IS_ERR(dest_page)) {
+ error = PTR_ERR(dest_page);
+ unlock_page(src_page);
+ put_page(src_page);
+ goto out_error;
+ }
+ src_addr = kmap_atomic(src_page);
+ dest_addr = kmap_atomic(dest_page);
+
+ flush_dcache_page(src_page);
+ flush_dcache_page(dest_page);
+
+ if (memcmp(src_addr + src_poff, dest_addr + dest_poff, cmp_len))
+ same = false;
+
+ kunmap_atomic(dest_addr);
+ kunmap_atomic(src_addr);
+ unlock_page(dest_page);
+ unlock_page(src_page);
+ put_page(dest_page);
+ put_page(src_page);
+
+ if (!same)
+ break;
+
+ srcoff += cmp_len;
+ destoff += cmp_len;
+ len -= cmp_len;
+ }
+
+ *is_same = same;
+ return 0;
+
+out_error:
+ trace_xfs_reflink_compare_extents_error(XFS_I(dest), error, _RET_IP_);
+ return error;
+}
+
+/*
* Link a range of blocks from one file to another.
*/
int
@@ -1239,12 +1344,14 @@ xfs_reflink_remap_range(
xfs_off_t srcoff,
struct xfs_inode *dest,
xfs_off_t destoff,
- xfs_off_t len)
+ xfs_off_t len,
+ unsigned int flags)
{
struct xfs_mount *mp = src->i_mount;
xfs_fileoff_t sfsbno, dfsbno;
xfs_filblks_t fsblen;
int error;
+ bool is_same;

if (!xfs_sb_version_hasreflink(&mp->m_sb))
return -EOPNOTSUPP;
@@ -1256,6 +1363,9 @@ xfs_reflink_remap_range(
if (XFS_IS_REALTIME_INODE(src) || XFS_IS_REALTIME_INODE(dest))
return -EINVAL;

+ if (flags & ~XFS_REFLINK_ALL)
+ return -EINVAL;
+
trace_xfs_reflink_remap_range(src, srcoff, len, dest, destoff);

/* Lock both files against IO */
@@ -1267,6 +1377,21 @@ xfs_reflink_remap_range(
xfs_lock_two_inodes(src, dest, XFS_MMAPLOCK_EXCL);
}

+ /*
+ * Check that the extents are the same.
+ */
+ if (flags & XFS_REFLINK_DEDUPE) {
+ is_same = false;
+ error = xfs_compare_extents(VFS_I(src), srcoff, VFS_I(dest),
+ destoff, len, &is_same);
+ if (error)
+ goto out_error;
+ if (!is_same) {
+ error = -EBADE;
+ goto out_error;
+ }
+ }
+
error = xfs_reflink_set_inode_flag(src, dest);
if (error)
goto out_error;
diff --git a/fs/xfs/xfs_reflink.h b/fs/xfs/xfs_reflink.h
index 92c0ebd..1d38b97 100644
--- a/fs/xfs/xfs_reflink.h
+++ b/fs/xfs/xfs_reflink.h
@@ -43,8 +43,11 @@ extern int xfs_reflink_end_cow(struct xfs_inode *ip, xfs_off_t offset,

extern int xfs_reflink_recover_cow(struct xfs_mount *mp);

+#define XFS_REFLINK_DEDUPE 1 /* only reflink if contents match */
+#define XFS_REFLINK_ALL (XFS_REFLINK_DEDUPE)
extern int xfs_reflink_remap_range(struct xfs_inode *src, xfs_off_t srcoff,
- struct xfs_inode *dest, xfs_off_t destoff, xfs_off_t len);
+ struct xfs_inode *dest, xfs_off_t destoff, xfs_off_t len,
+ unsigned int flags);

/* xfs_aops.c */
extern int xfs_map_cow_blocks(struct inode *inode, xfs_off_t offset,