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xfs: teach get_bmapx about shared extents and the CoW fork
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Teach xfs_getbmapx how to report shared extents and CoW fork contents
accurately in the bmap output by querying the refcount btree
appropriately.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Darrick J. Wong committed Oct 5, 2016
1 parent cc71466 commit f86f403
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Showing 2 changed files with 143 additions and 15 deletions.
4 changes: 3 additions & 1 deletion fs/xfs/libxfs/xfs_fs.h
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Original file line number Diff line number Diff line change
Expand Up @@ -81,14 +81,16 @@ struct getbmapx {
#define BMV_IF_PREALLOC 0x4 /* rtn status BMV_OF_PREALLOC if req */
#define BMV_IF_DELALLOC 0x8 /* rtn status BMV_OF_DELALLOC if req */
#define BMV_IF_NO_HOLES 0x10 /* Do not return holes */
#define BMV_IF_COWFORK 0x20 /* return CoW fork rather than data */
#define BMV_IF_VALID \
(BMV_IF_ATTRFORK|BMV_IF_NO_DMAPI_READ|BMV_IF_PREALLOC| \
BMV_IF_DELALLOC|BMV_IF_NO_HOLES)
BMV_IF_DELALLOC|BMV_IF_NO_HOLES|BMV_IF_COWFORK)

/* bmv_oflags values - returned for each non-header segment */
#define BMV_OF_PREALLOC 0x1 /* segment = unwritten pre-allocation */
#define BMV_OF_DELALLOC 0x2 /* segment = delayed allocation */
#define BMV_OF_LAST 0x4 /* segment is the last in the file */
#define BMV_OF_SHARED 0x8 /* segment shared with another file */

/*
* Structure for XFS_IOC_FSSETDM.
Expand Down
154 changes: 140 additions & 14 deletions fs/xfs/xfs_bmap_util.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -42,6 +42,9 @@
#include "xfs_icache.h"
#include "xfs_log.h"
#include "xfs_rmap_btree.h"
#include "xfs_iomap.h"
#include "xfs_reflink.h"
#include "xfs_refcount.h"

/* Kernel only BMAP related definitions and functions */

Expand Down Expand Up @@ -389,11 +392,13 @@ xfs_bmap_count_blocks(
STATIC int
xfs_getbmapx_fix_eof_hole(
xfs_inode_t *ip, /* xfs incore inode pointer */
int whichfork,
struct getbmapx *out, /* output structure */
int prealloced, /* this is a file with
* preallocated data space */
__int64_t end, /* last block requested */
xfs_fsblock_t startblock)
xfs_fsblock_t startblock,
bool moretocome)
{
__int64_t fixlen;
xfs_mount_t *mp; /* file system mount point */
Expand All @@ -418,15 +423,91 @@ xfs_getbmapx_fix_eof_hole(
else
out->bmv_block = xfs_fsb_to_db(ip, startblock);
fileblock = XFS_BB_TO_FSB(ip->i_mount, out->bmv_offset);
ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
if (xfs_iext_bno_to_ext(ifp, fileblock, &lastx) &&
ifp = XFS_IFORK_PTR(ip, whichfork);
if (!moretocome &&
xfs_iext_bno_to_ext(ifp, fileblock, &lastx) &&
(lastx == (ifp->if_bytes / (uint)sizeof(xfs_bmbt_rec_t))-1))
out->bmv_oflags |= BMV_OF_LAST;
}

return 1;
}

/* Adjust the reported bmap around shared/unshared extent transitions. */
STATIC int
xfs_getbmap_adjust_shared(
struct xfs_inode *ip,
int whichfork,
struct xfs_bmbt_irec *map,
struct getbmapx *out,
struct xfs_bmbt_irec *next_map)
{
struct xfs_mount *mp = ip->i_mount;
xfs_agnumber_t agno;
xfs_agblock_t agbno;
xfs_agblock_t ebno;
xfs_extlen_t elen;
xfs_extlen_t nlen;
int error;

next_map->br_startblock = NULLFSBLOCK;
next_map->br_startoff = NULLFILEOFF;
next_map->br_blockcount = 0;

/* Only written data blocks can be shared. */
if (!xfs_is_reflink_inode(ip) || whichfork != XFS_DATA_FORK ||
map->br_startblock == DELAYSTARTBLOCK ||
map->br_startblock == HOLESTARTBLOCK ||
ISUNWRITTEN(map))
return 0;

agno = XFS_FSB_TO_AGNO(mp, map->br_startblock);
agbno = XFS_FSB_TO_AGBNO(mp, map->br_startblock);
error = xfs_reflink_find_shared(mp, agno, agbno, map->br_blockcount,
&ebno, &elen, true);
if (error)
return error;

if (ebno == NULLAGBLOCK) {
/* No shared blocks at all. */
return 0;
} else if (agbno == ebno) {
/*
* Shared extent at (agbno, elen). Shrink the reported
* extent length and prepare to move the start of map[i]
* to agbno+elen, with the aim of (re)formatting the new
* map[i] the next time through the inner loop.
*/
out->bmv_length = XFS_FSB_TO_BB(mp, elen);
out->bmv_oflags |= BMV_OF_SHARED;
if (elen != map->br_blockcount) {
*next_map = *map;
next_map->br_startblock += elen;
next_map->br_startoff += elen;
next_map->br_blockcount -= elen;
}
map->br_blockcount -= elen;
} else {
/*
* There's an unshared extent (agbno, ebno - agbno)
* followed by shared extent at (ebno, elen). Shrink
* the reported extent length to cover only the unshared
* extent and prepare to move up the start of map[i] to
* ebno, with the aim of (re)formatting the new map[i]
* the next time through the inner loop.
*/
*next_map = *map;
nlen = ebno - agbno;
out->bmv_length = XFS_FSB_TO_BB(mp, nlen);
next_map->br_startblock += nlen;
next_map->br_startoff += nlen;
next_map->br_blockcount -= nlen;
map->br_blockcount -= nlen;
}

return 0;
}

/*
* Get inode's extents as described in bmv, and format for output.
* Calls formatter to fill the user's buffer until all extents
Expand Down Expand Up @@ -459,12 +540,28 @@ xfs_getbmap(
int iflags; /* interface flags */
int bmapi_flags; /* flags for xfs_bmapi */
int cur_ext = 0;
struct xfs_bmbt_irec inject_map;

mp = ip->i_mount;
iflags = bmv->bmv_iflags;
whichfork = iflags & BMV_IF_ATTRFORK ? XFS_ATTR_FORK : XFS_DATA_FORK;

if (whichfork == XFS_ATTR_FORK) {
#ifndef DEBUG
/* Only allow CoW fork queries if we're debugging. */
if (iflags & BMV_IF_COWFORK)
return -EINVAL;
#endif
if ((iflags & BMV_IF_ATTRFORK) && (iflags & BMV_IF_COWFORK))
return -EINVAL;

if (iflags & BMV_IF_ATTRFORK)
whichfork = XFS_ATTR_FORK;
else if (iflags & BMV_IF_COWFORK)
whichfork = XFS_COW_FORK;
else
whichfork = XFS_DATA_FORK;

switch (whichfork) {
case XFS_ATTR_FORK:
if (XFS_IFORK_Q(ip)) {
if (ip->i_d.di_aformat != XFS_DINODE_FMT_EXTENTS &&
ip->i_d.di_aformat != XFS_DINODE_FMT_BTREE &&
Expand All @@ -480,7 +577,15 @@ xfs_getbmap(

prealloced = 0;
fixlen = 1LL << 32;
} else {
break;
case XFS_COW_FORK:
if (ip->i_cformat != XFS_DINODE_FMT_EXTENTS)
return -EINVAL;

prealloced = 0;
fixlen = XFS_ISIZE(ip);
break;
default:
if (ip->i_d.di_format != XFS_DINODE_FMT_EXTENTS &&
ip->i_d.di_format != XFS_DINODE_FMT_BTREE &&
ip->i_d.di_format != XFS_DINODE_FMT_LOCAL)
Expand All @@ -494,6 +599,7 @@ xfs_getbmap(
prealloced = 0;
fixlen = XFS_ISIZE(ip);
}
break;
}

if (bmv->bmv_length == -1) {
Expand All @@ -520,7 +626,8 @@ xfs_getbmap(
return -ENOMEM;

xfs_ilock(ip, XFS_IOLOCK_SHARED);
if (whichfork == XFS_DATA_FORK) {
switch (whichfork) {
case XFS_DATA_FORK:
if (!(iflags & BMV_IF_DELALLOC) &&
(ip->i_delayed_blks || XFS_ISIZE(ip) > ip->i_d.di_size)) {
error = filemap_write_and_wait(VFS_I(ip)->i_mapping);
Expand All @@ -538,8 +645,14 @@ xfs_getbmap(
}

lock = xfs_ilock_data_map_shared(ip);
} else {
break;
case XFS_COW_FORK:
lock = XFS_ILOCK_SHARED;
xfs_ilock(ip, lock);
break;
case XFS_ATTR_FORK:
lock = xfs_ilock_attr_map_shared(ip);
break;
}

/*
Expand Down Expand Up @@ -581,7 +694,8 @@ xfs_getbmap(
goto out_free_map;
ASSERT(nmap <= subnex);

for (i = 0; i < nmap && nexleft && bmv->bmv_length; i++) {
for (i = 0; i < nmap && nexleft && bmv->bmv_length &&
cur_ext < bmv->bmv_count; i++) {
out[cur_ext].bmv_oflags = 0;
if (map[i].br_state == XFS_EXT_UNWRITTEN)
out[cur_ext].bmv_oflags |= BMV_OF_PREALLOC;
Expand Down Expand Up @@ -614,9 +728,16 @@ xfs_getbmap(
goto out_free_map;
}

if (!xfs_getbmapx_fix_eof_hole(ip, &out[cur_ext],
prealloced, bmvend,
map[i].br_startblock))
/* Is this a shared block? */
error = xfs_getbmap_adjust_shared(ip, whichfork,
&map[i], &out[cur_ext], &inject_map);
if (error)
goto out_free_map;

if (!xfs_getbmapx_fix_eof_hole(ip, whichfork,
&out[cur_ext], prealloced, bmvend,
map[i].br_startblock,
inject_map.br_startblock != NULLFSBLOCK))
goto out_free_map;

bmv->bmv_offset =
Expand All @@ -636,11 +757,16 @@ xfs_getbmap(
continue;
}

nexleft--;
if (inject_map.br_startblock != NULLFSBLOCK) {
map[i] = inject_map;
i--;
} else
nexleft--;
bmv->bmv_entries++;
cur_ext++;
}
} while (nmap && nexleft && bmv->bmv_length);
} while (nmap && nexleft && bmv->bmv_length &&
cur_ext < bmv->bmv_count);

out_free_map:
kmem_free(map);
Expand Down

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