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xfs: factor extent map manipulations out of xfs_bmapi
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To further improve the readability of xfs_bmapi(), factor the pure
extent map manipulations out into separate functions. This removes
large blocks of logic from the xfs_bmapi() code loop and makes it
easier to see the operational logic flow for xfs_bmapi().
    
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>
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Dave Chinner authored and Alex Elder committed Oct 12, 2011
1 parent ecee76b commit aef9a89
Showing 1 changed file with 107 additions and 74 deletions.
181 changes: 107 additions & 74 deletions fs/xfs/xfs_bmap.c
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Original file line number Diff line number Diff line change
Expand Up @@ -4248,6 +4248,107 @@ xfs_bmap_validate_ret(
#endif /* DEBUG */


/*
* Trim the returned map to the required bounds
*/
STATIC void
xfs_bmapi_trim_map(
struct xfs_bmbt_irec *mval,
struct xfs_bmbt_irec *got,
xfs_fileoff_t *bno,
xfs_filblks_t len,
xfs_fileoff_t obno,
xfs_fileoff_t end,
int n,
int flags)
{
if ((flags & XFS_BMAPI_ENTIRE) ||
got->br_startoff + got->br_blockcount <= obno) {
*mval = *got;
if (isnullstartblock(got->br_startblock))
mval->br_startblock = DELAYSTARTBLOCK;
return;
}

if (obno > *bno)
*bno = obno;
ASSERT((*bno >= obno) || (n == 0));
ASSERT(*bno < end);
mval->br_startoff = *bno;
if (isnullstartblock(got->br_startblock))
mval->br_startblock = DELAYSTARTBLOCK;
else
mval->br_startblock = got->br_startblock +
(*bno - got->br_startoff);
/*
* Return the minimum of what we got and what we asked for for
* the length. We can use the len variable here because it is
* modified below and we could have been there before coming
* here if the first part of the allocation didn't overlap what
* was asked for.
*/
mval->br_blockcount = XFS_FILBLKS_MIN(end - *bno,
got->br_blockcount - (*bno - got->br_startoff));
mval->br_state = got->br_state;
ASSERT(mval->br_blockcount <= len);
return;
}

/*
* Update and validate the extent map to return
*/
STATIC void
xfs_bmapi_update_map(
struct xfs_bmbt_irec **map,
xfs_fileoff_t *bno,
xfs_filblks_t *len,
xfs_fileoff_t obno,
xfs_fileoff_t end,
int *n,
int flags)
{
xfs_bmbt_irec_t *mval = *map;

ASSERT((flags & XFS_BMAPI_ENTIRE) ||
((mval->br_startoff + mval->br_blockcount) <= end));
ASSERT((flags & XFS_BMAPI_ENTIRE) || (mval->br_blockcount <= *len) ||
(mval->br_startoff < obno));

*bno = mval->br_startoff + mval->br_blockcount;
*len = end - *bno;
if (*n > 0 && mval->br_startoff == mval[-1].br_startoff) {
/* update previous map with new information */
ASSERT(mval->br_startblock == mval[-1].br_startblock);
ASSERT(mval->br_blockcount > mval[-1].br_blockcount);
ASSERT(mval->br_state == mval[-1].br_state);
mval[-1].br_blockcount = mval->br_blockcount;
mval[-1].br_state = mval->br_state;
} else if (*n > 0 && mval->br_startblock != DELAYSTARTBLOCK &&
mval[-1].br_startblock != DELAYSTARTBLOCK &&
mval[-1].br_startblock != HOLESTARTBLOCK &&
mval->br_startblock == mval[-1].br_startblock +
mval[-1].br_blockcount &&
((flags & XFS_BMAPI_IGSTATE) ||
mval[-1].br_state == mval->br_state)) {
ASSERT(mval->br_startoff ==
mval[-1].br_startoff + mval[-1].br_blockcount);
mval[-1].br_blockcount += mval->br_blockcount;
} else if (*n > 0 &&
mval->br_startblock == DELAYSTARTBLOCK &&
mval[-1].br_startblock == DELAYSTARTBLOCK &&
mval->br_startoff ==
mval[-1].br_startoff + mval[-1].br_blockcount) {
mval[-1].br_blockcount += mval->br_blockcount;
mval[-1].br_state = mval->br_state;
} else if (!((*n == 0) &&
((mval->br_startoff + mval->br_blockcount) <=
obno))) {
mval++;
(*n)++;
}
*map = mval;
}

/*
* Map file blocks to filesystem blocks.
* File range is given by the bno/len pair.
Expand Down Expand Up @@ -4650,44 +4751,9 @@ xfs_bmapi(
n++;
continue;
}
/*
* Then deal with the allocated space we found.
*/
ASSERT(ep != NULL);
if (!(flags & XFS_BMAPI_ENTIRE) &&
(got.br_startoff + got.br_blockcount > obno)) {
if (obno > bno)
bno = obno;
ASSERT((bno >= obno) || (n == 0));
ASSERT(bno < end);
mval->br_startoff = bno;
if (isnullstartblock(got.br_startblock)) {
ASSERT(!wr || (flags & XFS_BMAPI_DELAY));
mval->br_startblock = DELAYSTARTBLOCK;
} else
mval->br_startblock =
got.br_startblock +
(bno - got.br_startoff);
/*
* Return the minimum of what we got and what we
* asked for for the length. We can use the len
* variable here because it is modified below
* and we could have been there before coming
* here if the first part of the allocation
* didn't overlap what was asked for.
*/
mval->br_blockcount =
XFS_FILBLKS_MIN(end - bno, got.br_blockcount -
(bno - got.br_startoff));
mval->br_state = got.br_state;
ASSERT(mval->br_blockcount <= len);
} else {
*mval = got;
if (isnullstartblock(mval->br_startblock)) {
ASSERT(!wr || (flags & XFS_BMAPI_DELAY));
mval->br_startblock = DELAYSTARTBLOCK;
}
}

/* Deal with the allocated space we found. */
xfs_bmapi_trim_map(mval, &got, &bno, len, obno, end, n, flags);

/*
* Check if writing previously allocated but
Expand Down Expand Up @@ -4730,42 +4796,9 @@ xfs_bmapi(
continue;
}

ASSERT((flags & XFS_BMAPI_ENTIRE) ||
((mval->br_startoff + mval->br_blockcount) <= end));
ASSERT((flags & XFS_BMAPI_ENTIRE) ||
(mval->br_blockcount <= len) ||
(mval->br_startoff < obno));
bno = mval->br_startoff + mval->br_blockcount;
len = end - bno;
if (n > 0 && mval->br_startoff == mval[-1].br_startoff) {
ASSERT(mval->br_startblock == mval[-1].br_startblock);
ASSERT(mval->br_blockcount > mval[-1].br_blockcount);
ASSERT(mval->br_state == mval[-1].br_state);
mval[-1].br_blockcount = mval->br_blockcount;
mval[-1].br_state = mval->br_state;
} else if (n > 0 && mval->br_startblock != DELAYSTARTBLOCK &&
mval[-1].br_startblock != DELAYSTARTBLOCK &&
mval[-1].br_startblock != HOLESTARTBLOCK &&
mval->br_startblock ==
mval[-1].br_startblock + mval[-1].br_blockcount &&
((flags & XFS_BMAPI_IGSTATE) ||
mval[-1].br_state == mval->br_state)) {
ASSERT(mval->br_startoff ==
mval[-1].br_startoff + mval[-1].br_blockcount);
mval[-1].br_blockcount += mval->br_blockcount;
} else if (n > 0 &&
mval->br_startblock == DELAYSTARTBLOCK &&
mval[-1].br_startblock == DELAYSTARTBLOCK &&
mval->br_startoff ==
mval[-1].br_startoff + mval[-1].br_blockcount) {
mval[-1].br_blockcount += mval->br_blockcount;
mval[-1].br_state = mval->br_state;
} else if (!((n == 0) &&
((mval->br_startoff + mval->br_blockcount) <=
obno))) {
mval++;
n++;
}
/* update the extent map to return */
xfs_bmapi_update_map(&mval, &bno, &len, obno, end, &n, flags);

/*
* If we're done, stop now. Stop when we've allocated
* XFS_BMAP_MAX_NMAP extents no matter what. Otherwise
Expand Down

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