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xfs: don't rely on extent indices in xfs_bmap_collapse_extents 

Rewrite xfs_bmap_collapse_extents so that we don't rely on extent indices
except for iterating over them.  Not being able to iterate to the next
extent is a sufficient exit condition, and we don't need to do any extent
count games given that:

  a) we already flushed all delalloc extents past our start offset
     before doing the operation
  b) xfs_iext_count() includes delalloc extents anyway

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Christoph Hellwig 2017-10-19 11:08:51 -07:00 committed by Darrick J. Wong
parent 11f75b3bba
commit 40591bdbcc
1 changed files with 13 additions and 43 deletions
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56
fs/xfs/libxfs/xfs_bmap.c
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@ -5637,8 +5637,6 @@ xfs_bmap_collapse_extents(
struct xfs_btree_cur *cur = NULL;
struct xfs_bmbt_irec got, prev;
xfs_extnum_t current_ext;
xfs_extnum_t total_extents;
xfs_extnum_t stop_extent;
xfs_fileoff_t new_startoff;
int error = 0;
int logflags = 0;
@ -5669,52 +5667,31 @@ xfs_bmap_collapse_extents(
cur->bc_private.b.flags = 0;
}
/*
* There may be delalloc extents in the data fork before the range we
* are collapsing out, so we cannot use the count of real extents here.
* Instead we have to calculate it from the incore fork.
*/
total_extents = xfs_iext_count(ifp);
if (total_extents == 0) {
*done = true;
goto del_cursor;
}
/*
* Look up the extent index for the fsb where we start shifting. We can
* henceforth iterate with current_ext as extent list changes are locked
* out via ilock.
*
* If next_fsb lies in a hole beyond which there are no extents we are
* done.
*/
if (!xfs_iext_lookup_extent(ip, ifp, *next_fsb, &current_ext, &got)) {
*done = true;
goto del_cursor;
}
XFS_WANT_CORRUPTED_RETURN(mp, !isnullstartblock(got.br_startblock));
stop_extent = total_extents;
if (current_ext >= stop_extent) {
error = -EIO;
goto del_cursor;
}
new_startoff = got.br_startoff - offset_shift_fsb;
if (current_ext) {
xfs_iext_get_extent(ifp, current_ext - 1, &prev);
if (xfs_iext_get_extent(ifp, current_ext - 1, &prev)) {
if (new_startoff < prev.br_startoff + prev.br_blockcount) {
error = -EINVAL;
goto del_cursor;
}
/* check whether to merge the extent or shift it down */
if (xfs_bmse_can_merge(&prev, &got, offset_shift_fsb)) {
error = xfs_bmse_merge(ip, whichfork, offset_shift_fsb,
current_ext, &got, &prev, cur,
&logflags, dfops);
if (error)
goto del_cursor;
/* update got after merge */
if (!xfs_iext_get_extent(ifp, current_ext, &got)) {
*done = true;
goto del_cursor;
}
goto done;
}
} else {
@ -5728,20 +5705,13 @@ xfs_bmap_collapse_extents(
cur, &logflags, dfops, new_startoff);
if (error)
goto del_cursor;
current_ext++;
done:
/*
* If there was an extent merge during the shift, the extent
* count can change. Update the total and grade the next record.
*/
total_extents = xfs_iext_count(ifp);
stop_extent = total_extents;
if (current_ext == stop_extent) {
*done = true;
goto del_cursor;
}
xfs_iext_get_extent(ifp, current_ext, &got);
if (!xfs_iext_get_extent(ifp, ++current_ext, &got)) {
*done = true;
goto del_cursor;
}
done:
*next_fsb = got.br_startoff;
del_cursor:
if (cur)