btrfs: offline dedupe

This patch adds an ioctl, BTRFS_IOC_FILE_EXTENT_SAME which will try to
de-duplicate a list of extents across a range of files.

Internally, the ioctl re-uses code from the clone ioctl. This avoids
rewriting a large chunk of extent handling code.

Userspace passes in an array of file, offset pairs along with a length
argument. The ioctl will then (for each dedupe) do a byte-by-byte comparison
of the user data before deduping the extent. Status and number of bytes
deduped are returned for each operation.

Signed-off-by: Mark Fasheh <mfasheh@suse.de>
Reviewed-by: Zach Brown <zab@redhat.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

1 files changed, 279 insertions, 0 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 5b5148a1b0d3..022d8364e072 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -43,6 +43,7 @@
 #include <linux/blkdev.h>
 #include <linux/uuid.h>
 #include <linux/btrfs.h>
+#include <linux/uaccess.h>
 #include "compat.h"
 #include "ctree.h"
 #include "disk-io.h"
@@ -57,6 +58,9 @@
 #include "send.h"
 #include "dev-replace.h"
 
+static int btrfs_clone(struct inode *src, struct inode *inode,
+                       u64 off, u64 olen, u64 olen_aligned, u64 destoff);
+
 /* Mask out flags that are inappropriate for the given type of inode. */
 static inline __u32 btrfs_mask_flags(umode_t mode, __u32 flags)
 {
@@ -2470,6 +2474,34 @@ out:
         return ret;
 }
 
+static struct page *extent_same_get_page(struct inode *inode, u64 off)
+{
+        struct page *page;
+        pgoff_t index;
+        struct extent_io_tree *tree = &BTRFS_I(inode)->io_tree;
+
+        index = off >> PAGE_CACHE_SHIFT;
+
+        page = grab_cache_page(inode->i_mapping, index);
+        if (!page)
+                return NULL;
+
+        if (!PageUptodate(page)) {
+                if (extent_read_full_page_nolock(tree, page, btrfs_get_extent,
+                                                 0))
+                        return NULL;
+                lock_page(page);
+                if (!PageUptodate(page)) {
+                        unlock_page(page);
+                        page_cache_release(page);
+                        return NULL;
+                }
+        }
+        unlock_page(page);
+
+        return page;
+}
+
 static inline void lock_extent_range(struct inode *inode, u64 off, u64 len)
 {
         /* do any pending delalloc/csum calc on src, one way or
@@ -2490,6 +2522,251 @@ static inline void lock_extent_range(struct inode *inode, u64 off, u64 len)
         }
 }
 
+static void btrfs_double_unlock(struct inode *inode1, u64 loff1,
+                                struct inode *inode2, u64 loff2, u64 len)
+{
+        unlock_extent(&BTRFS_I(inode1)->io_tree, loff1, loff1 + len - 1);
+        unlock_extent(&BTRFS_I(inode2)->io_tree, loff2, loff2 + len - 1);
+
+        mutex_unlock(&inode1->i_mutex);
+        mutex_unlock(&inode2->i_mutex);
+}
+
+static void btrfs_double_lock(struct inode *inode1, u64 loff1,
+                              struct inode *inode2, u64 loff2, u64 len)
+{
+        if (inode1 < inode2) {
+                swap(inode1, inode2);
+                swap(loff1, loff2);
+        }
+
+        mutex_lock_nested(&inode1->i_mutex, I_MUTEX_PARENT);
+        lock_extent_range(inode1, loff1, len);
+        if (inode1 != inode2) {
+                mutex_lock_nested(&inode2->i_mutex, I_MUTEX_CHILD);
+                lock_extent_range(inode2, loff2, len);
+        }
+}
+
+static int btrfs_cmp_data(struct inode *src, u64 loff, struct inode *dst,
+                          u64 dst_loff, u64 len)
+{
+        int ret = 0;
+        struct page *src_page, *dst_page;
+        unsigned int cmp_len = PAGE_CACHE_SIZE;
+        void *addr, *dst_addr;
+
+        while (len) {
+                if (len < PAGE_CACHE_SIZE)
+                        cmp_len = len;
+
+                src_page = extent_same_get_page(src, loff);
+                if (!src_page)
+                        return -EINVAL;
+                dst_page = extent_same_get_page(dst, dst_loff);
+                if (!dst_page) {
+                        page_cache_release(src_page);
+                        return -EINVAL;
+                }
+                addr = kmap_atomic(src_page);
+                dst_addr = kmap_atomic(dst_page);
+
+                flush_dcache_page(src_page);
+                flush_dcache_page(dst_page);
+
+                if (memcmp(addr, dst_addr, cmp_len))
+                        ret = BTRFS_SAME_DATA_DIFFERS;
+
+                kunmap_atomic(addr);
+                kunmap_atomic(dst_addr);
+                page_cache_release(src_page);
+                page_cache_release(dst_page);
+
+                if (ret)
+                        break;
+
+                loff += cmp_len;
+                dst_loff += cmp_len;
+                len -= cmp_len;
+        }
+
+        return ret;
+}
+
+static int extent_same_check_offsets(struct inode *inode, u64 off, u64 len)
+{
+        u64 bs = BTRFS_I(inode)->root->fs_info->sb->s_blocksize;
+
+        if (off + len > inode->i_size || off + len < off)
+                return -EINVAL;
+        /* Check that we are block aligned - btrfs_clone() requires this */
+        if (!IS_ALIGNED(off, bs) || !IS_ALIGNED(off + len, bs))
+                return -EINVAL;
+
+        return 0;
+}
+
+static int btrfs_extent_same(struct inode *src, u64 loff, u64 len,
+                             struct inode *dst, u64 dst_loff)
+{
+        int ret;
+
+        /*
+         * btrfs_clone() can't handle extents in the same file
+         * yet. Once that works, we can drop this check and replace it
+         * with a check for the same inode, but overlapping extents.
+         */
+        if (src == dst)
+                return -EINVAL;
+
+        btrfs_double_lock(src, loff, dst, dst_loff, len);
+
+        ret = extent_same_check_offsets(src, loff, len);
+        if (ret)
+                goto out_unlock;
+
+        ret = extent_same_check_offsets(dst, dst_loff, len);
+        if (ret)
+                goto out_unlock;
+
+        /* don't make the dst file partly checksummed */
+        if ((BTRFS_I(src)->flags & BTRFS_INODE_NODATASUM) !=
+            (BTRFS_I(dst)->flags & BTRFS_INODE_NODATASUM)) {
+                ret = -EINVAL;
+                goto out_unlock;
+        }
+
+        ret = btrfs_cmp_data(src, loff, dst, dst_loff, len);
+        if (ret == 0)
+                ret = btrfs_clone(src, dst, loff, len, len, dst_loff);
+
+out_unlock:
+        btrfs_double_unlock(src, loff, dst, dst_loff, len);
+
+        return ret;
+}
+
+#define BTRFS_MAX_DEDUPE_LEN    (16 * 1024 * 1024)
+
+static long btrfs_ioctl_file_extent_same(struct file *file,
+                                         void __user *argp)
+{
+        struct btrfs_ioctl_same_args *args = argp;
+        struct btrfs_ioctl_same_args same;
+        struct btrfs_ioctl_same_extent_info info;
+        struct inode *src = file->f_dentry->d_inode;
+        struct file *dst_file = NULL;
+        struct inode *dst;
+        u64 off;
+        u64 len;
+        int i;
+        int ret;
+        u64 bs = BTRFS_I(src)->root->fs_info->sb->s_blocksize;
+        bool is_admin = capable(CAP_SYS_ADMIN);
+
+        if (!(file->f_mode & FMODE_READ))
+                return -EINVAL;
+
+        ret = mnt_want_write_file(file);
+        if (ret)
+                return ret;
+
+        if (copy_from_user(&same,
+                           (struct btrfs_ioctl_same_args __user *)argp,
+                           sizeof(same))) {
+                ret = -EFAULT;
+                goto out;
+        }
+
+        off = same.logical_offset;
+        len = same.length;
+
+        /*
+         * 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 > BTRFS_MAX_DEDUPE_LEN)
+                len = BTRFS_MAX_DEDUPE_LEN;
+
+        if (WARN_ON_ONCE(bs < PAGE_CACHE_SIZE)) {
+                /*
+                 * Btrfs does not support blocksize < page_size. As a
+                 * result, btrfs_cmp_data() won't correctly handle
+                 * this situation without an update.
+                 */
+                ret = -EINVAL;
+                goto out;
+        }
+
+        ret = -EISDIR;
+        if (S_ISDIR(src->i_mode))
+                goto out;
+
+        ret = -EACCES;
+        if (!S_ISREG(src->i_mode))
+                goto out;
+
+        ret = 0;
+        for (i = 0; i < same.dest_count; i++) {
+                if (copy_from_user(&info, &args->info[i], sizeof(info))) {
+                        ret = -EFAULT;
+                        goto out;
+                }
+
+                info.bytes_deduped = 0;
+
+                dst_file = fget(info.fd);
+                if (!dst_file) {
+                        info.status = -EBADF;
+                        goto next;
+                }
+
+                if (!(is_admin || (dst_file->f_mode & FMODE_WRITE))) {
+                        info.status = -EINVAL;
+                        goto next;
+                }
+
+                info.status = -EXDEV;
+                if (file->f_path.mnt != dst_file->f_path.mnt)
+                        goto next;
+
+                dst = dst_file->f_dentry->d_inode;
+                if (src->i_sb != dst->i_sb)
+                        goto next;
+
+                if (S_ISDIR(dst->i_mode)) {
+                        info.status = -EISDIR;
+                        goto next;
+                }
+
+                if (!S_ISREG(dst->i_mode)) {
+                        info.status = -EACCES;
+                        goto next;
+                }
+
+                info.status = btrfs_extent_same(src, off, len, dst,
+                                                info.logical_offset);
+                if (info.status == 0)
+                        info.bytes_deduped += len;
+
+next:
+                if (dst_file)
+                        fput(dst_file);
+
+                if (__put_user_unaligned(info.status, &args->info[i].status) ||
+                    __put_user_unaligned(info.bytes_deduped,
+                                         &args->info[i].bytes_deduped)) {
+                        ret = -EFAULT;
+                        goto out;
+                }                                                               
+        }
+
+out:
+        mnt_drop_write_file(file);
+        return ret;
+}
+
 /**
  * btrfs_clone() - clone a range from inode file to another
  *
@@ -4242,6 +4519,8 @@ long btrfs_ioctl(struct file *file, unsigned int
                 return btrfs_ioctl_get_fslabel(file, argp);
         case BTRFS_IOC_SET_FSLABEL:
                 return btrfs_ioctl_set_fslabel(file, argp);
+        case BTRFS_IOC_FILE_EXTENT_SAME:
+                return btrfs_ioctl_file_extent_same(file, argp);
         }
 
         return -ENOTTY;