xfs: teach get_bmapx about shared extents and the CoW fork

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>

diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
index 6f4f2c3..3d1efe5 100644 (file)
--- a/fs/xfs/libxfs/xfs_fs.h
+++ b/fs/xfs/libxfs/xfs_fs.h
@@ -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.

diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
index e827d65..f7b3f02 100644 (file)
--- a/fs/xfs/xfs_bmap_util.c
+++ b/fs/xfs/xfs_bmap_util.c
@@ -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 */
 
@@ -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 */
@@ -418,8 +423,9 @@ 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;
        }
@@ -427,6 +433,81 @@ xfs_getbmapx_fix_eof_hole(
        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
@@ -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 &&
@@ -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)
@@ -494,6 +599,7 @@ xfs_getbmap(
                        prealloced = 0;
                        fixlen = XFS_ISIZE(ip);
                }
+               break;
        }
 
        if (bmv->bmv_length == -1) {
@@ -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);
@@ -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;
        }
 
        /*
@@ -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;
@@ -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 =
@@ -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);