[PATCH 56/58] xfs: unshare a range of blocks via fallocate

Darrick J. Wong
2015-10-07T05:01:29Z

Now that we have an fallocate flag to unshare a range of blocks, make
XFS actually implement it.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
fs/xfs/xfs_file.c | 11 ++
fs/xfs/xfs_reflink.c | 321 ++++++++++++++++++++++++++++++++++++++++++++++++++
fs/xfs/xfs_reflink.h | 3
3 files changed, 334 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index fc5b9ea..5756046 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -905,7 +905,7 @@ buffered:
#define XFS_FALLOC_FL_SUPPORTED \
(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE | \
FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE | \
- FALLOC_FL_INSERT_RANGE)
+ FALLOC_FL_INSERT_RANGE | FALLOC_FL_UNSHARE_RANGE)

STATIC long
xfs_file_fallocate(
@@ -982,6 +982,15 @@ xfs_file_fallocate(
goto out_unlock;
}
do_file_insert = 1;
+ } else if (mode & FALLOC_FL_UNSHARE_RANGE) {
+ if (offset + len > i_size_read(inode)) {
+ error = -EINVAL;
+ goto out_unlock;
+ }
+
+ error = xfs_reflink_unshare(ip, file, offset, len);
+ if (error)
+ goto out_unlock;
} else {
flags |= XFS_PREALLOC_SET;

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index dee3556..92d8345 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -1571,3 +1571,324 @@ out_error:
trace_xfs_reflink_range_error(dest, error, _RET_IP_);
return error;
}
+
+/**
+ * xfs_reflink_dirty_range() -- Dirty all the shared blocks in the file so that
+ * they're rewritten elsewhere. Similar to generic_perform_write().
+ *
+ * @filp: VFS file pointer
+ * @pos: offset to start dirtying
+ * @len: number of bytes to dirty
+ */
+STATIC int
+xfs_reflink_dirty_range(
+ struct file *filp,
+ xfs_off_t pos,
+ xfs_off_t len)
+{
+ struct address_space *mapping;
+ const struct address_space_operations *a_ops;
+ int error;
+ unsigned int flags;
+ struct page *page;
+ struct page *rpage;
+ unsigned long offset; /* Offset into pagecache page */
+ unsigned long bytes; /* Bytes to write to page */
+ void *fsdata;
+
+ mapping = filp->f_mapping;
+ a_ops = mapping->a_ops;
+ flags = AOP_FLAG_UNINTERRUPTIBLE;
+ do {
+
+ offset = (pos & (PAGE_CACHE_SIZE - 1));
+ bytes = min_t(unsigned long, len, PAGE_CACHE_SIZE) - offset;
+ rpage = xfs_get_page(file_inode(filp), pos);
+ if (IS_ERR(rpage)) {
+ error = PTR_ERR(rpage);
+ break;
+ } else if (!rpage) {
+ error = -ENOMEM;
+ break;
+ }
+
+ error = a_ops->write_begin(filp, mapping, pos, bytes, flags,
+ &page, &fsdata);
+ page_cache_release(rpage);
+ if (error < 0)
+ break;
+
+ trace_xfs_reflink_unshare_page(file_inode(filp), page,
+ pos, bytes);
+
+ if (!PageUptodate(page)) {
+ pr_err("%s: STALE? ino=%lu pos=%llu\n",
+ __func__, filp->f_inode->i_ino, pos);
+ WARN_ON(1);
+ }
+ if (mapping_writably_mapped(mapping))
+ flush_dcache_page(page);
+
+ error = a_ops->write_end(filp, mapping, pos, bytes, bytes,
+ page, fsdata);
+ if (error < 0)
+ break;
+ else if (error == 0) {
+ error = -EIO;
+ break;
+ } else {
+ bytes = error;
+ error = 0;
+ }
+
+ cond_resched();
+
+ pos += bytes;
+ len -= bytes;
+
+ balance_dirty_pages_ratelimited(mapping);
+ if (fatal_signal_pending(current)) {
+ error = -EINTR;
+ break;
+ }
+ } while (len > 0);
+
+ return error;
+}
+
+/*
+ * The user wants to preemptively CoW all shared blocks in this file,
+ * which enables us to turn off the reflink flag. Iterate all
+ * extents which are not prealloc/delalloc to see which ranges are
+ * mentioned in the refcount tree, then read those blocks into the
+ * pagecache, dirty them, fsync them back out, and then we can update
+ * the inode flag. What happens if we run out of memory? :)
+ */
+STATIC int
+xfs_reflink_dirty_extents(
+ struct xfs_inode *ip,
+ struct file *filp,
+ xfs_fileoff_t fbno,
+ xfs_filblks_t end,
+ xfs_off_t isize)
+{
+ struct xfs_mount *mp = ip->i_mount;
+ xfs_agnumber_t agno;
+ xfs_agblock_t agbno;
+ xfs_extlen_t rlen;
+ xfs_nlink_t nr;
+ xfs_off_t fpos;
+ xfs_off_t flen;
+ struct xfs_bmbt_irec map[2];
+ int nmaps;
+ int error;
+
+ while (end - fbno > 0) {
+ nmaps = 1;
+ /*
+ * Look for extents in the file. Skip holes, delalloc, or
+ * unwritten extents; they can't be reflinked.
+ */
+ error = xfs_bmapi_read(ip, fbno, end - fbno, map, &nmaps, 0);
+ if (error)
+ goto out;
+ if (nmaps == 0)
+ break;
+ if (map[0].br_startblock == HOLESTARTBLOCK ||
+ map[0].br_startblock == DELAYSTARTBLOCK ||
+ ISUNWRITTEN(&map[0]))
+ goto next;
+
+ map[1] = map[0];
+ while (map[1].br_blockcount) {
+ agno = XFS_FSB_TO_AGNO(mp, map[1].br_startblock);
+ agbno = XFS_FSB_TO_AGBNO(mp, map[1].br_startblock);
+ CHECK_AG_NUMBER(mp, agno);
+ CHECK_AG_EXTENT(mp, agbno, 1);
+
+ error = xfs_reflink_get_refcount(mp, agno, agbno,
+ &rlen, &nr);
+ if (error)
+ goto out;
+ XFS_WANT_CORRUPTED_GOTO(mp, rlen != 0, out);
+ if (rlen > map[1].br_blockcount)
+ rlen = map[1].br_blockcount;
+ if (nr < 2)
+ goto skip_copy;
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ fpos = XFS_FSB_TO_B(mp, map[1].br_startoff);
+ flen = XFS_FSB_TO_B(mp, rlen);
+ if (fpos + flen > isize)
+ flen = isize - fpos;
+ error = xfs_reflink_dirty_range(filp, fpos, flen);
+ xfs_ilock(ip, XFS_ILOCK_EXCL);
+ if (error)
+ goto out;
+skip_copy:
+ map[1].br_blockcount -= rlen;
+ map[1].br_startoff += rlen;
+ map[1].br_startblock += rlen;
+ }
+
+next:
+ fbno = map[0].br_startoff + map[0].br_blockcount;
+ }
+out:
+ return error;
+}
+
+/* Iterate the extents; if there are no reflinked blocks, clear the flag. */
+STATIC int
+xfs_reflink_try_clear_inode_flag(
+ struct xfs_inode *ip,
+ xfs_off_t old_isize)
+{
+ struct xfs_mount *mp = ip->i_mount;
+ struct xfs_trans *tp;
+ xfs_fileoff_t fbno;
+ xfs_filblks_t end;
+ xfs_agnumber_t agno;
+ xfs_agblock_t agbno;
+ xfs_extlen_t rlen;
+ xfs_nlink_t nr;
+ struct xfs_bmbt_irec map[2];
+ int nmaps;
+ int error = 0;
+
+ xfs_ilock(ip, XFS_ILOCK_EXCL);
+
+ if (old_isize != i_size_read(VFS_I(ip)))
+ goto out;
+ if (!(ip->i_d.di_flags2 & XFS_DIFLAG2_REFLINK))
+ goto out;
+
+ fbno = 0;
+ end = XFS_B_TO_FSB(mp, old_isize);
+ while (end - fbno > 0) {
+ nmaps = 1;
+ /*
+ * Look for extents in the file. Skip holes, delalloc, or
+ * unwritten extents; they can't be reflinked.
+ */
+ error = xfs_bmapi_read(ip, fbno, end - fbno, map, &nmaps, 0);
+ if (error)
+ goto out;
+ if (nmaps == 0)
+ break;
+ if (map[0].br_startblock == HOLESTARTBLOCK ||
+ map[0].br_startblock == DELAYSTARTBLOCK ||
+ ISUNWRITTEN(&map[0]))
+ goto next;
+
+ map[1] = map[0];
+ while (map[1].br_blockcount) {
+ agno = XFS_FSB_TO_AGNO(mp, map[1].br_startblock);
+ agbno = XFS_FSB_TO_AGBNO(mp, map[1].br_startblock);
+ CHECK_AG_NUMBER(mp, agno);
+ CHECK_AG_EXTENT(mp, agbno, 1);
+
+ error = xfs_reflink_get_refcount(mp, agno, agbno,
+ &rlen, &nr);
+ if (error)
+ goto out;
+ XFS_WANT_CORRUPTED_GOTO(mp, rlen != 0, out);
+ if (rlen > map[1].br_blockcount)
+ rlen = map[1].br_blockcount;
+ /* Someone else is reflinking */
+ if (nr >= 2) {
+ error = 0;
+ goto out;
+ }
+
+ map[1].br_blockcount -= rlen;
+ map[1].br_startoff += rlen;
+ map[1].br_startblock += rlen;
+ }
+
+next:
+ fbno = map[0].br_startoff + map[0].br_blockcount;
+ }
+
+ /* No reflinked blocks, so clear the flag */
+ tp = xfs_trans_alloc(mp, XFS_TRANS_SETATTR_NOT_SIZE);
+ error = xfs_trans_reserve(tp, &M_RES(mp)->tr_ichange, 0, 0);
+ if (error) {
+ xfs_trans_cancel(tp);
+ goto out;
+ }
+ trace_xfs_reflink_unset_inode_flag(ip);
+ xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
+ ip->i_d.di_flags2 &= ~XFS_DIFLAG2_REFLINK;
+ xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
+ error = xfs_trans_commit(tp);
+ if (error) {
+ xfs_trans_cancel(tp);
+ goto out;
+ }
+
+ return 0;
+out:
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+ return error;
+}
+
+/**
+ * xfs_reflink_unshare() - Pre-COW all shared blocks within a given range
+ * of a file and turn off the reflink flag if we
+ * unshare all of the file's blocks.
+ * @ip: XFS inode
+ * @filp: VFS file structure
+ * @offset: Offset to start
+ * @len: Length to ...
+ */
+int
+xfs_reflink_unshare(
+ struct xfs_inode *ip,
+ struct file *filp,
+ xfs_off_t offset,
+ xfs_off_t len)
+{
+ struct xfs_mount *mp = ip->i_mount;
+ xfs_fileoff_t fbno;
+ xfs_filblks_t end;
+ xfs_off_t old_isize, isize;
+ int error;
+
+ if (!xfs_sb_version_hasreflink(&ip->i_mount->m_sb) ||
+ !xfs_is_reflink_inode(ip))
+ return 0;
+
+ trace_xfs_reflink_unshare(ip);
+
+ inode_dio_wait(VFS_I(ip));
+
+ /* Try to CoW the selected ranges */
+ xfs_ilock(ip, XFS_ILOCK_EXCL);
+ fbno = XFS_B_TO_FSB(mp, offset);
+ old_isize = isize = i_size_read(VFS_I(ip));
+ end = XFS_B_TO_FSB(mp, offset + len);
+ error = xfs_reflink_dirty_extents(ip, filp, fbno, end, isize);
+ if (error)
+ goto out_unlock;
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+
+ /* Wait for the IO to finish */
+ error = filemap_write_and_wait(filp->f_mapping);
+ if (error)
+ goto out;
+
+ /* Turn off the reflink flag if we unshared the whole file */
+ if (offset == 0 && len == isize) {
+ error = xfs_reflink_try_clear_inode_flag(ip, old_isize);
+ if (error)
+ goto out;
+ }
+
+ return 0;
+
+out_unlock:
+ xfs_iunlock(ip, XFS_ILOCK_EXCL);
+out:
+ trace_xfs_reflink_unshare_error(ip, error, _RET_IP_);
+ return error;
+}
diff --git a/fs/xfs/xfs_reflink.h b/fs/xfs/xfs_reflink.h
index c60a9bd..4ce2cba6 100644
--- a/fs/xfs/xfs_reflink.h
+++ b/fs/xfs/xfs_reflink.h
@@ -51,4 +51,7 @@ extern int xfs_reflink(struct xfs_inode *src, xfs_off_t srcoff,
struct xfs_inode *dest, xfs_off_t destoff, xfs_off_t len,
unsigned int flags);

+extern int xfs_reflink_unshare(struct xfs_inode *ip, struct file *filp,
+ xfs_off_t offset, xfs_off_t len);
+
#endif /* __XFS_REFLINK_H */