[PATCH 48/58] xfs: copy-on-write reflinked blocks when zeroing ranges of blocks

Darrick J. Wong
2015-10-07T05:00:30Z

When we're writing zeroes to a reflinked block (such as when we're
punching a reflinked range), we need to fork the the block and write
to that, otherwise we can corrupt the other reflinks.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
fs/xfs/xfs_bmap_util.c | 25 +++++++-
fs/xfs/xfs_reflink.c | 154 ++++++++++++++++++++++++++++++++++++++++++++++++
fs/xfs/xfs_reflink.h | 6 ++
3 files changed, 183 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index 245a34a..b054b28 100644
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -41,6 +41,7 @@
#include "xfs_icache.h"
#include "xfs_log.h"
#include "xfs_rmap_btree.h"
+#include "xfs_reflink.h"

/* Kernel only BMAP related definitions and functions */

@@ -1095,7 +1096,9 @@ xfs_zero_remaining_bytes(
xfs_buf_t *bp;
xfs_mount_t *mp = ip->i_mount;
int nimap;
- int error = 0;
+ int error = 0, err2;
+ bool should_fork;
+ struct xfs_trans *tp;

/*
* Avoid doing I/O beyond eof - it's not necessary
@@ -1136,8 +1139,14 @@ xfs_zero_remaining_bytes(
if (lastoffset > endoff)
lastoffset = endoff;

+ /* Do we need to CoW this block? */
+ error = xfs_reflink_should_fork_block(ip, &imap, offset,
+ &should_fork);
+ if (error)
+ return error;
+
/* DAX can just zero the backing device directly */
- if (IS_DAX(VFS_I(ip))) {
+ if (IS_DAX(VFS_I(ip)) && !should_fork) {
error = dax_zero_page_range(VFS_I(ip), offset,
lastoffset - offset + 1,
xfs_get_blocks_direct);
@@ -1158,10 +1167,22 @@ xfs_zero_remaining_bytes(
(offset - XFS_FSB_TO_B(mp, imap.br_startoff)),
0, lastoffset - offset + 1);

+ tp = NULL;
+ if (should_fork) {
+ error = xfs_reflink_fork_buf(ip, bp, offset_fsb, &tp);
+ if (error)
+ return error;
+ }
+
error = xfs_bwrite(bp);
+
+ err2 = xfs_reflink_finish_fork_buf(ip, bp, offset_fsb, tp,
+ error, imap.br_startblock);
xfs_buf_relse(bp);
if (error)
return error;
+ if (err2)
+ return err2;
}
return error;
}
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 226e23f..f5eed2f 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -788,3 +788,157 @@ xfs_reflink_add_ioend(
{
list_add_tail(&eio->rlei_list, &ioend->io_reflink_endio_list);
}
+
+/**
+ * xfs_reflink_fork_buf() - start a transaction to fork a buffer (if needed)
+ *
+ * @mp: XFS mount point
+ * @ip: XFS inode
+ * @bp: the buffer that we might need to fork
+ * @fileoff: file offset of the buffer
+ * @ptp: pointer to an XFS transaction
+ */
+int
+xfs_reflink_fork_buf(
+ struct xfs_inode *ip,
+ struct xfs_buf *bp,
+ xfs_fileoff_t fileoff,
+ struct xfs_trans **ptp)
+{
+ struct xfs_mount *mp = ip->i_mount;
+ struct xfs_trans *tp;
+ xfs_fsblock_t fsbno;
+ xfs_fsblock_t new_fsbno;
+ xfs_agnumber_t agno;
+ xfs_agblock_t agbno;
+ uint resblks;
+ int error;
+
+ fsbno = XFS_DADDR_TO_FSB(mp, XFS_BUF_ADDR(bp));
+ agno = XFS_FSB_TO_AGNO(mp, fsbno);
+ agbno = XFS_FSB_TO_AGBNO(mp, fsbno);
+ CHECK_AG_NUMBER(mp, agno);
+ CHECK_AG_EXTENT(mp, agno, 1);
+
+ /*
+ * Get ready to remap the thing...
+ */
+ resblks = XFS_DIOSTRAT_SPACE_RES(mp, 3);
+ tp = xfs_trans_alloc(mp, XFS_TRANS_STRAT_WRITE);
+ error = xfs_trans_reserve(tp, &M_RES(mp)->tr_write, resblks, 0);
+
+ /*
+ * check for running out of space
+ */
+ if (error) {
+ /*
+ * Free the transaction structure.
+ */
+ ASSERT(error == -ENOSPC || XFS_FORCED_SHUTDOWN(mp));
+ goto out_cancel;
+ }
+ error = xfs_trans_reserve_quota(tp, mp,
+ ip->i_udquot, ip->i_gdquot, ip->i_pdquot,
+ resblks, 0, XFS_QMOPT_RES_REGBLKS);
+ if (error)
+ goto out_cancel;
+
+ xfs_ilock(ip, XFS_ILOCK_EXCL);
+ xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
+
+ /* fork block, remap buffer */
+ error = fork_one_block(mp, tp, ip, fsbno, &new_fsbno, fileoff);
+ if (error)
+ goto out_cancel;
+
+ trace_xfs_reflink_fork_buf(ip, fileoff, fsbno, 1, new_fsbno);
+
+ XFS_BUF_SET_ADDR(bp, XFS_FSB_TO_DADDR(mp, new_fsbno));
+ *ptp = tp;
+ return error;
+
+out_cancel:
+ xfs_trans_cancel(tp);
+ trace_xfs_reflink_fork_buf_error(ip, error, _RET_IP_);
+ return error;
+}
+
+/**
+ * xfs_reflink_finish_fork_buf() - finish forking a file buffer
+ *
+ * @ip: XFS inode
+ * @bp: the buffer that was forked
+ * @fileoff: file offset of the buffer
+ * @tp: transaction that was returned from xfs_reflink_fork_buf()
+ * @write_error: status code from writing the block
+ */
+int
+xfs_reflink_finish_fork_buf(
+ struct xfs_inode *ip,
+ struct xfs_buf *bp,
+ xfs_fileoff_t fileoff,
+ struct xfs_trans *tp,
+ int write_error,
+ xfs_fsblock_t old_fsbno)
+{
+ struct xfs_mount *mp = ip->i_mount;
+ struct xfs_bmap_free free_list;
+ xfs_fsblock_t firstfsb;
+ xfs_fsblock_t fsbno;
+ struct xfs_bmbt_irec imaps[1];
+ xfs_agnumber_t agno;
+ int nimaps = 1;
+ int done;
+ int error = write_error;
+ int committed;
+ struct xfs_owner_info oinfo;
+
+ if (tp == NULL)
+ return 0;
+
+ fsbno = XFS_DADDR_TO_FSB(mp, XFS_BUF_ADDR(bp));
+ agno = XFS_FSB_TO_AGNO(mp, fsbno);
+ XFS_RMAP_INO_OWNER(&oinfo, ip->i_ino, XFS_DATA_FORK, fileoff);
+ if (write_error != 0)
+ goto out_write_error;
+
+ trace_xfs_reflink_fork_buf(ip, fileoff, old_fsbno, 1, fsbno);
+ /*
+ * Remap the old blocks.
+ */
+ xfs_bmap_init(&free_list, &firstfsb);
+ error = xfs_bunmapi(tp, ip, fileoff, 1, 0, 1, &firstfsb, &free_list,
+ &done);
+ if (error)
+ goto out_free;
+ ASSERT(done == 1);
+
+ error = xfs_bmapi_write(tp, ip, fileoff, 1, XFS_BMAPI_REMAP, &fsbno,
+ 1, &imaps[0], &nimaps, &free_list);
+ if (error)
+ goto out_free;
+
+ /*
+ * complete the transaction
+ */
+ error = xfs_bmap_finish(&tp, &free_list, &committed);
+ if (error)
+ goto out_cancel;
+
+ error = xfs_trans_commit(tp);
+ if (error)
+ goto out_error;
+
+ return error;
+out_free:
+ xfs_bmap_finish(&tp, &free_list, &committed);
+out_write_error:
+ done = xfs_free_extent(tp, fsbno, 1, &oinfo);
+ if (error == 0)
+ error = done;
+out_cancel:
+ xfs_trans_cancel(tp);
+out_error:
+ trace_xfs_reflink_finish_fork_buf_error(ip, error, _RET_IP_);
+ return error;
+}
diff --git a/fs/xfs/xfs_reflink.h b/fs/xfs/xfs_reflink.h
index b3e12d2..ce00cf6 100644
--- a/fs/xfs/xfs_reflink.h
+++ b/fs/xfs/xfs_reflink.h
@@ -38,4 +38,10 @@ extern void xfs_reflink_add_ioend(struct xfs_ioend *ioend,
extern int xfs_reflink_should_fork_block(struct xfs_inode *ip,
struct xfs_bmbt_irec *imap, xfs_off_t offset, bool *type);

+extern int xfs_reflink_fork_buf(struct xfs_inode *ip, struct xfs_buf *bp,
+ xfs_fileoff_t fileoff, struct xfs_trans **ptp);
+extern int xfs_reflink_finish_fork_buf(struct xfs_inode *ip, struct xfs_buf *bp,
+ xfs_fileoff_t fileoff, struct xfs_trans *tp, int write_error,
+ xfs_fsblock_t old_fsbno);
+
#endif /* __XFS_REFLINK_H */