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xfs: introduce the CoW fork 

Introduce a new in-core fork for storing copy-on-write delalloc
reservations and allocated extents that are in the process of being
written out.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Darrick J. Wong 2016-10-03 09:11:32 -07:00
parent 11715a21bc
commit 3993baeb3c
13 changed files with 264 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
fs/xfs/Makefile
View File

@ -90,6 +90,7 @@ xfs-y += xfs_aops.o \
xfs_message.o \
xfs_mount.o \
xfs_mru_cache.o \
xfs_reflink.o \
xfs_stats.o \
xfs_super.o \
xfs_symlink.o \

27
fs/xfs/libxfs/xfs_bmap.c
View File

@ -2924,6 +2924,7 @@ xfs_bmap_add_extent_hole_real(
ASSERT(!isnullstartblock(new->br_startblock));
ASSERT(!bma->cur ||
!(bma->cur->bc_private.b.flags & XFS_BTCUR_BPRV_WASDEL));
ASSERT(whichfork != XFS_COW_FORK);
XFS_STATS_INC(mp, xs_add_exlist);
@ -4072,12 +4073,11 @@ xfs_bmapi_read(
int error;
int eof;
int n = 0;
int whichfork = (flags & XFS_BMAPI_ATTRFORK) ?
XFS_ATTR_FORK : XFS_DATA_FORK;
int whichfork = xfs_bmapi_whichfork(flags);
ASSERT(*nmap >= 1);
ASSERT(!(flags & ~(XFS_BMAPI_ATTRFORK|XFS_BMAPI_ENTIRE|
XFS_BMAPI_IGSTATE)));
XFS_BMAPI_IGSTATE|XFS_BMAPI_COWFORK)));
ASSERT(xfs_isilocked(ip, XFS_ILOCK_SHARED|XFS_ILOCK_EXCL));
if (unlikely(XFS_TEST_ERROR(
@ -4095,6 +4095,16 @@ xfs_bmapi_read(
ifp = XFS_IFORK_PTR(ip, whichfork);
/* No CoW fork? Return a hole. */
if (whichfork == XFS_COW_FORK && !ifp) {
mval->br_startoff = bno;
mval->br_startblock = HOLESTARTBLOCK;
mval->br_blockcount = len;
mval->br_state = XFS_EXT_NORM;
*nmap = 1;
return 0;
}
if (!(ifp->if_flags & XFS_IFEXTENTS)) {
error = xfs_iread_extents(NULL, ip, whichfork);
if (error)
@ -4368,8 +4378,7 @@ xfs_bmapi_convert_unwritten(
xfs_filblks_t len,
int flags)
{
int whichfork = (flags & XFS_BMAPI_ATTRFORK) ?
XFS_ATTR_FORK : XFS_DATA_FORK;
int whichfork = xfs_bmapi_whichfork(flags);
struct xfs_ifork *ifp = XFS_IFORK_PTR(bma->ip, whichfork);
int tmp_logflags = 0;
int error;
@ -4385,6 +4394,8 @@ xfs_bmapi_convert_unwritten(
(XFS_BMAPI_PREALLOC | XFS_BMAPI_CONVERT))
return 0;
ASSERT(whichfork != XFS_COW_FORK);
/*
* Modify (by adding) the state flag, if writing.
*/
@ -4795,6 +4806,8 @@ xfs_bmap_del_extent(
if (whichfork == XFS_ATTR_FORK)
state |= BMAP_ATTRFORK;
else if (whichfork == XFS_COW_FORK)
state |= BMAP_COWFORK;
ifp = XFS_IFORK_PTR(ip, whichfork);
ASSERT((*idx >= 0) && (*idx < ifp->if_bytes /
@ -5133,8 +5146,8 @@ __xfs_bunmapi(
trace_xfs_bunmap(ip, bno, len, flags, _RET_IP_);
whichfork = (flags & XFS_BMAPI_ATTRFORK) ?
XFS_ATTR_FORK : XFS_DATA_FORK;
whichfork = xfs_bmapi_whichfork(flags);
ASSERT(whichfork != XFS_COW_FORK);
ifp = XFS_IFORK_PTR(ip, whichfork);
if (unlikely(
XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS &&

22
fs/xfs/libxfs/xfs_bmap.h
View File

@ -107,6 +107,9 @@ struct xfs_extent_free_item
*/
#define XFS_BMAPI_REMAP 0x100
/* Map something in the CoW fork. */
#define XFS_BMAPI_COWFORK 0x200
#define XFS_BMAPI_FLAGS \
{ XFS_BMAPI_ENTIRE, "ENTIRE" }, \
{ XFS_BMAPI_METADATA, "METADATA" }, \
@ -116,12 +119,23 @@ struct xfs_extent_free_item
{ XFS_BMAPI_CONTIG, "CONTIG" }, \
{ XFS_BMAPI_CONVERT, "CONVERT" }, \
{ XFS_BMAPI_ZERO, "ZERO" }, \
{ XFS_BMAPI_REMAP, "REMAP" }
{ XFS_BMAPI_REMAP, "REMAP" }, \
{ XFS_BMAPI_COWFORK, "COWFORK" }
static inline int xfs_bmapi_aflag(int w)
{
return (w == XFS_ATTR_FORK ? XFS_BMAPI_ATTRFORK : 0);
return (w == XFS_ATTR_FORK ? XFS_BMAPI_ATTRFORK :
(w == XFS_COW_FORK ? XFS_BMAPI_COWFORK : 0));
}
static inline int xfs_bmapi_whichfork(int bmapi_flags)
{
if (bmapi_flags & XFS_BMAPI_COWFORK)
return XFS_COW_FORK;
else if (bmapi_flags & XFS_BMAPI_ATTRFORK)
return XFS_ATTR_FORK;
return XFS_DATA_FORK;
}
/*
@ -142,13 +156,15 @@ static inline int xfs_bmapi_aflag(int w)
#define BMAP_LEFT_VALID (1 << 6)
#define BMAP_RIGHT_VALID (1 << 7)
#define BMAP_ATTRFORK (1 << 8)
#define BMAP_COWFORK (1 << 9)
#define XFS_BMAP_EXT_FLAGS \
{ BMAP_LEFT_CONTIG, "LC" }, \
{ BMAP_RIGHT_CONTIG, "RC" }, \
{ BMAP_LEFT_FILLING, "LF" }, \
{ BMAP_RIGHT_FILLING, "RF" }, \
{ BMAP_ATTRFORK, "ATTR" }
{ BMAP_ATTRFORK, "ATTR" }, \
{ BMAP_COWFORK, "COW" }
/*

1
fs/xfs/libxfs/xfs_bmap_btree.c
View File

@ -777,6 +777,7 @@ xfs_bmbt_init_cursor(
{
struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, whichfork);
struct xfs_btree_cur *cur;
ASSERT(whichfork != XFS_COW_FORK);
cur = kmem_zone_zalloc(xfs_btree_cur_zone, KM_SLEEP);

47
fs/xfs/libxfs/xfs_inode_fork.c
View File

@ -206,9 +206,14 @@ xfs_iformat_fork(
XFS_ERROR_REPORT("xfs_iformat(7)", XFS_ERRLEVEL_LOW, ip->i_mount);
return -EFSCORRUPTED;
}
if (error) {
if (error)
return error;
if (xfs_is_reflink_inode(ip)) {
ASSERT(ip->i_cowfp == NULL);
xfs_ifork_init_cow(ip);
}
if (!XFS_DFORK_Q(dip))
return 0;
@ -247,6 +252,9 @@ xfs_iformat_fork(
if (error) {
kmem_zone_free(xfs_ifork_zone, ip->i_afp);
ip->i_afp = NULL;
if (ip->i_cowfp)
kmem_zone_free(xfs_ifork_zone, ip->i_cowfp);
ip->i_cowfp = NULL;
xfs_idestroy_fork(ip, XFS_DATA_FORK);
}
return error;
@ -761,6 +769,9 @@ xfs_idestroy_fork(
if (whichfork == XFS_ATTR_FORK) {
kmem_zone_free(xfs_ifork_zone, ip->i_afp);
ip->i_afp = NULL;
} else if (whichfork == XFS_COW_FORK) {
kmem_zone_free(xfs_ifork_zone, ip->i_cowfp);
ip->i_cowfp = NULL;
}
}
@ -948,6 +959,19 @@ xfs_iext_get_ext(
}
}
/* Convert bmap state flags to an inode fork. */
struct xfs_ifork *
xfs_iext_state_to_fork(
struct xfs_inode *ip,
int state)
{
if (state & BMAP_COWFORK)
return ip->i_cowfp;
else if (state & BMAP_ATTRFORK)
return ip->i_afp;
return &ip->i_df;
}
/*
* Insert new item(s) into the extent records for incore inode
* fork 'ifp'. 'count' new items are inserted at index 'idx'.
@ -960,7 +984,7 @@ xfs_iext_insert(
xfs_bmbt_irec_t *new, /* items to insert */
int state) /* type of extent conversion */
{
xfs_ifork_t *ifp = (state & BMAP_ATTRFORK) ? ip->i_afp : &ip->i_df;
xfs_ifork_t *ifp = xfs_iext_state_to_fork(ip, state);
xfs_extnum_t i; /* extent record index */
trace_xfs_iext_insert(ip, idx, new, state, _RET_IP_);
@ -1210,7 +1234,7 @@ xfs_iext_remove(
int ext_diff, /* number of extents to remove */
int state) /* type of extent conversion */
{
xfs_ifork_t *ifp = (state & BMAP_ATTRFORK) ? ip->i_afp : &ip->i_df;
xfs_ifork_t *ifp = xfs_iext_state_to_fork(ip, state);
xfs_extnum_t nextents; /* number of extents in file */
int new_size; /* size of extents after removal */
@ -1955,3 +1979,20 @@ xfs_iext_irec_update_extoffs(
ifp->if_u1.if_ext_irec[i].er_extoff += ext_diff;
}
}
/*
* Initialize an inode's copy-on-write fork.
*/
void
xfs_ifork_init_cow(
struct xfs_inode *ip)
{
if (ip->i_cowfp)
return;
ip->i_cowfp = kmem_zone_zalloc(xfs_ifork_zone,
KM_SLEEP | KM_NOFS);
ip->i_cowfp->if_flags = XFS_IFEXTENTS;
ip->i_cformat = XFS_DINODE_FMT_EXTENTS;
ip->i_cnextents = 0;
}

28
fs/xfs/libxfs/xfs_inode_fork.h
View File

@ -92,7 +92,9 @@ typedef struct xfs_ifork {
#define XFS_IFORK_PTR(ip,w) \
((w) == XFS_DATA_FORK ? \
&(ip)->i_df : \
(ip)->i_afp)
((w) == XFS_ATTR_FORK ? \
(ip)->i_afp : \
(ip)->i_cowfp))
#define XFS_IFORK_DSIZE(ip) \
(XFS_IFORK_Q(ip) ? \
XFS_IFORK_BOFF(ip) : \
@ -105,26 +107,38 @@ typedef struct xfs_ifork {
#define XFS_IFORK_SIZE(ip,w) \
((w) == XFS_DATA_FORK ? \
XFS_IFORK_DSIZE(ip) : \
XFS_IFORK_ASIZE(ip))
((w) == XFS_ATTR_FORK ? \
XFS_IFORK_ASIZE(ip) : \
0))
#define XFS_IFORK_FORMAT(ip,w) \
((w) == XFS_DATA_FORK ? \
(ip)->i_d.di_format : \
(ip)->i_d.di_aformat)
((w) == XFS_ATTR_FORK ? \
(ip)->i_d.di_aformat : \
(ip)->i_cformat))
#define XFS_IFORK_FMT_SET(ip,w,n) \
((w) == XFS_DATA_FORK ? \
((ip)->i_d.di_format = (n)) : \
((ip)->i_d.di_aformat = (n)))
((w) == XFS_ATTR_FORK ? \
((ip)->i_d.di_aformat = (n)) : \
((ip)->i_cformat = (n))))
#define XFS_IFORK_NEXTENTS(ip,w) \
((w) == XFS_DATA_FORK ? \
(ip)->i_d.di_nextents : \
(ip)->i_d.di_anextents)
((w) == XFS_ATTR_FORK ? \
(ip)->i_d.di_anextents : \
(ip)->i_cnextents))
#define XFS_IFORK_NEXT_SET(ip,w,n) \
((w) == XFS_DATA_FORK ? \
((ip)->i_d.di_nextents = (n)) : \
((ip)->i_d.di_anextents = (n)))
((w) == XFS_ATTR_FORK ? \
((ip)->i_d.di_anextents = (n)) : \
((ip)->i_cnextents = (n))))
#define XFS_IFORK_MAXEXT(ip, w) \
(XFS_IFORK_SIZE(ip, w) / sizeof(xfs_bmbt_rec_t))
struct xfs_ifork *xfs_iext_state_to_fork(struct xfs_inode *ip, int state);
int xfs_iformat_fork(struct xfs_inode *, struct xfs_dinode *);
void xfs_iflush_fork(struct xfs_inode *, struct xfs_dinode *,
struct xfs_inode_log_item *, int);
@ -169,4 +183,6 @@ void xfs_iext_irec_update_extoffs(struct xfs_ifork *, int, int);
extern struct kmem_zone *xfs_ifork_zone;
extern void xfs_ifork_init_cow(struct xfs_inode *ip);
#endif /* __XFS_INODE_FORK_H__ */

15
fs/xfs/libxfs/xfs_rmap.c
View File

@ -1263,9 +1263,10 @@ out_cur:
*/
static bool
xfs_rmap_update_is_needed(
struct xfs_mount *mp)
struct xfs_mount *mp,
int whichfork)
{
return xfs_sb_version_hasrmapbt(&mp->m_sb);
return xfs_sb_version_hasrmapbt(&mp->m_sb) && whichfork != XFS_COW_FORK;
}
/*
@ -1311,7 +1312,7 @@ xfs_rmap_map_extent(
int whichfork,
struct xfs_bmbt_irec *PREV)
{
if (!xfs_rmap_update_is_needed(mp))
if (!xfs_rmap_update_is_needed(mp, whichfork))
return 0;
return __xfs_rmap_add(mp, dfops, XFS_RMAP_MAP, ip->i_ino,
@ -1327,7 +1328,7 @@ xfs_rmap_unmap_extent(
int whichfork,
struct xfs_bmbt_irec *PREV)
{
if (!xfs_rmap_update_is_needed(mp))
if (!xfs_rmap_update_is_needed(mp, whichfork))
return 0;
return __xfs_rmap_add(mp, dfops, XFS_RMAP_UNMAP, ip->i_ino,
@ -1343,7 +1344,7 @@ xfs_rmap_convert_extent(
int whichfork,
struct xfs_bmbt_irec *PREV)
{
if (!xfs_rmap_update_is_needed(mp))
if (!xfs_rmap_update_is_needed(mp, whichfork))
return 0;
return __xfs_rmap_add(mp, dfops, XFS_RMAP_CONVERT, ip->i_ino,
@ -1362,7 +1363,7 @@ xfs_rmap_alloc_extent(
{
struct xfs_bmbt_irec bmap;
if (!xfs_rmap_update_is_needed(mp))
if (!xfs_rmap_update_is_needed(mp, XFS_DATA_FORK))
return 0;
bmap.br_startblock = XFS_AGB_TO_FSB(mp, agno, bno);
@ -1386,7 +1387,7 @@ xfs_rmap_free_extent(
{
struct xfs_bmbt_irec bmap;
if (!xfs_rmap_update_is_needed(mp))
if (!xfs_rmap_update_is_needed(mp, XFS_DATA_FORK))
return 0;
bmap.br_startblock = XFS_AGB_TO_FSB(mp, agno, bno);

1
fs/xfs/libxfs/xfs_types.h
View File

@ -90,6 +90,7 @@ typedef __int64_t xfs_sfiloff_t; /* signed block number in a file */
*/
#define XFS_DATA_FORK 0
#define XFS_ATTR_FORK 1
#define XFS_COW_FORK 2
/*
* Min numbers of data/attr fork btree root pointers.

5
fs/xfs/xfs_icache.c
View File

@ -76,6 +76,9 @@ xfs_inode_alloc(
ip->i_mount = mp;
memset(&ip->i_imap, 0, sizeof(struct xfs_imap));
ip->i_afp = NULL;
ip->i_cowfp = NULL;
ip->i_cnextents = 0;
ip->i_cformat = XFS_DINODE_FMT_EXTENTS;
memset(&ip->i_df, 0, sizeof(xfs_ifork_t));
ip->i_flags = 0;
ip->i_delayed_blks = 0;
@ -101,6 +104,8 @@ xfs_inode_free_callback(
if (ip->i_afp)
xfs_idestroy_fork(ip, XFS_ATTR_FORK);
if (ip->i_cowfp)
xfs_idestroy_fork(ip, XFS_COW_FORK);
if (ip->i_itemp) {
ASSERT(!(ip->i_itemp->ili_item.li_flags & XFS_LI_IN_AIL));

4
fs/xfs/xfs_inode.h
View File

@ -47,6 +47,7 @@ typedef struct xfs_inode {
/* Extent information. */
xfs_ifork_t *i_afp; /* attribute fork pointer */
xfs_ifork_t *i_cowfp; /* copy on write extents */
xfs_ifork_t i_df; /* data fork */
/* operations vectors */
@ -65,6 +66,9 @@ typedef struct xfs_inode {
struct xfs_icdinode i_d; /* most of ondisk inode */
xfs_extnum_t i_cnextents; /* # of extents in cow fork */
unsigned int i_cformat; /* format of cow fork */
/* VFS inode */
struct inode i_vnode; /* embedded VFS inode */
} xfs_inode_t;

114
fs/xfs/xfs_reflink.c Normal file
View File

@ -0,0 +1,114 @@
/*
* Copyright (C) 2016 Oracle. All Rights Reserved.
*
* Author: Darrick J. Wong <darrick.wong@oracle.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it would be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_defer.h"
#include "xfs_da_format.h"
#include "xfs_da_btree.h"
#include "xfs_inode.h"
#include "xfs_trans.h"
#include "xfs_inode_item.h"
#include "xfs_bmap.h"
#include "xfs_bmap_util.h"
#include "xfs_error.h"
#include "xfs_dir2.h"
#include "xfs_dir2_priv.h"
#include "xfs_ioctl.h"
#include "xfs_trace.h"
#include "xfs_log.h"
#include "xfs_icache.h"
#include "xfs_pnfs.h"
#include "xfs_refcount_btree.h"
#include "xfs_refcount.h"
#include "xfs_bmap_btree.h"
#include "xfs_trans_space.h"
#include "xfs_bit.h"
#include "xfs_alloc.h"
#include "xfs_quota_defs.h"
#include "xfs_quota.h"
#include "xfs_btree.h"
#include "xfs_bmap_btree.h"
#include "xfs_reflink.h"
/*
* Copy on Write of Shared Blocks
*
* XFS must preserve "the usual" file semantics even when two files share
* the same physical blocks. This means that a write to one file must not
* alter the blocks in a different file; the way that we'll do that is
* through the use of a copy-on-write mechanism. At a high level, that
* means that when we want to write to a shared block, we allocate a new
* block, write the data to the new block, and if that succeeds we map the
* new block into the file.
*
* XFS provides a "delayed allocation" mechanism that defers the allocation
* of disk blocks to dirty-but-not-yet-mapped file blocks as long as
* possible. This reduces fragmentation by enabling the filesystem to ask
* for bigger chunks less often, which is exactly what we want for CoW.
*
* The delalloc mechanism begins when the kernel wants to make a block
* writable (write_begin or page_mkwrite). If the offset is not mapped, we
* create a delalloc mapping, which is a regular in-core extent, but without
* a real startblock. (For delalloc mappings, the startblock encodes both
* a flag that this is a delalloc mapping, and a worst-case estimate of how
* many blocks might be required to put the mapping into the BMBT.) delalloc
* mappings are a reservation against the free space in the filesystem;
* adjacent mappings can also be combined into fewer larger mappings.
*
* When dirty pages are being written out (typically in writepage), the
* delalloc reservations are converted into real mappings by allocating
* blocks and replacing the delalloc mapping with real ones. A delalloc
* mapping can be replaced by several real ones if the free space is
* fragmented.
*
* We want to adapt the delalloc mechanism for copy-on-write, since the
* write paths are similar. The first two steps (creating the reservation
* and allocating the blocks) are exactly the same as delalloc except that
* the mappings must be stored in a separate CoW fork because we do not want
* to disturb the mapping in the data fork until we're sure that the write
* succeeded. IO completion in this case is the process of removing the old
* mapping from the data fork and moving the new mapping from the CoW fork to
* the data fork. This will be discussed shortly.
*
* For now, unaligned directio writes will be bounced back to the page cache.
* Block-aligned directio writes will use the same mechanism as buffered
* writes.
*
* CoW remapping must be done after the data block write completes,
* because we don't want to destroy the old data fork map until we're sure
* the new block has been written. Since the new mappings are kept in a
* separate fork, we can simply iterate these mappings to find the ones
* that cover the file blocks that we just CoW'd. For each extent, simply
* unmap the corresponding range in the data fork, map the new range into
* the data fork, and remove the extent from the CoW fork.
*
* Since the remapping operation can be applied to an arbitrary file
* range, we record the need for the remap step as a flag in the ioend
* instead of declaring a new IO type. This is required for direct io
* because we only have ioend for the whole dio, and we have to be able to
* remember the presence of unwritten blocks and CoW blocks with a single
* ioend structure. Better yet, the more ground we can cover with one
* ioend, the better.
*/

23
fs/xfs/xfs_reflink.h Normal file
View File

@ -0,0 +1,23 @@
/*
* Copyright (C) 2016 Oracle. All Rights Reserved.
*
* Author: Darrick J. Wong <darrick.wong@oracle.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it would be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#ifndef __XFS_REFLINK_H
#define __XFS_REFLINK_H 1
#endif /* __XFS_REFLINK_H */

4
fs/xfs/xfs_trace.h
View File

@ -269,10 +269,10 @@ DECLARE_EVENT_CLASS(xfs_bmap_class,
__field(unsigned long, caller_ip)
),
TP_fast_assign(
struct xfs_ifork *ifp = (state & BMAP_ATTRFORK) ?
ip->i_afp : &ip->i_df;
struct xfs_ifork *ifp;
struct xfs_bmbt_irec r;
ifp = xfs_iext_state_to_fork(ip, state);
xfs_bmbt_get_all(xfs_iext_get_ext(ifp, idx), &r);
__entry->dev = VFS_I(ip)->i_sb->s_dev;
__entry->ino = ip->i_ino;