}
/*
- * Remap parts of a file's data fork after a successful CoW.
+ * Remap part of the CoW fork into the data fork.
+ *
+ * We aim to remap the range starting at @offset_fsb and ending at @end_fsb
+ * into the data fork; this function will remap what it can (at the end of the
+ * range) and update @end_fsb appropriately. Each remap gets its own
+ * transaction because we can end up merging and splitting bmbt blocks for
+ * every remap operation and we'd like to keep the block reservation
+ * requirements as low as possible.
*/
-int
-xfs_reflink_end_cow(
- struct xfs_inode *ip,
- xfs_off_t offset,
- xfs_off_t count)
+STATIC int
+xfs_reflink_end_cow_extent(
+ struct xfs_inode *ip,
+ xfs_fileoff_t offset_fsb,
+ xfs_fileoff_t *end_fsb)
{
- struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
- struct xfs_bmbt_irec got, del;
- struct xfs_trans *tp;
- xfs_fileoff_t offset_fsb;
- xfs_fileoff_t end_fsb;
- int error;
- unsigned int resblks;
- xfs_filblks_t rlen;
- struct xfs_iext_cursor icur;
-
- trace_xfs_reflink_end_cow(ip, offset, count);
+ struct xfs_bmbt_irec got, del;
+ struct xfs_iext_cursor icur;
+ struct xfs_mount *mp = ip->i_mount;
+ struct xfs_trans *tp;
+ struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, XFS_COW_FORK);
+ xfs_filblks_t rlen;
+ unsigned int resblks;
+ int error;
/* No COW extents? That's easy! */
- if (ifp->if_bytes == 0)
+ if (ifp->if_bytes == 0) {
+ *end_fsb = offset_fsb;
return 0;
+ }
- offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
- end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count);
+ resblks = XFS_EXTENTADD_SPACE_RES(mp, XFS_DATA_FORK);
+ error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0,
+ XFS_TRANS_RESERVE | XFS_TRANS_NOFS, &tp);
+ if (error)
+ return error;
/*
- * Start a rolling transaction to switch the mappings. We're
- * unlikely ever to have to remap 16T worth of single-block
- * extents, so just cap the worst case extent count to 2^32-1.
- * Stick a warning in just in case, and avoid 64-bit division.
+ * Lock the inode. We have to ijoin without automatic unlock because
+ * the lead transaction is the refcountbt record deletion; the data
+ * fork update follows as a deferred log item.
*/
- BUILD_BUG_ON(MAX_RW_COUNT > UINT_MAX);
- if (end_fsb - offset_fsb > UINT_MAX) {
- error = -EFSCORRUPTED;
- xfs_force_shutdown(ip->i_mount, SHUTDOWN_CORRUPT_INCORE);
- ASSERT(0);
- goto out;
- }
- resblks = XFS_NEXTENTADD_SPACE_RES(ip->i_mount,
- (unsigned int)(end_fsb - offset_fsb),
- XFS_DATA_FORK);
- error = xfs_trans_alloc(ip->i_mount, &M_RES(ip->i_mount)->tr_write,
- resblks, 0, XFS_TRANS_RESERVE | XFS_TRANS_NOFS, &tp);
- if (error)
- goto out;
-
xfs_ilock(ip, XFS_ILOCK_EXCL);
xfs_trans_ijoin(tp, ip, 0);
* left by the time I/O completes for the loser of the race. In that
* case we are done.
*/
- if (!xfs_iext_lookup_extent_before(ip, ifp, &end_fsb, &icur, &got))
+ if (!xfs_iext_lookup_extent_before(ip, ifp, end_fsb, &icur, &got) ||
+ got.br_startoff + got.br_blockcount <= offset_fsb) {
+ *end_fsb = offset_fsb;
goto out_cancel;
+ }
- /* Walk backwards until we're out of the I/O range... */
- while (got.br_startoff + got.br_blockcount > offset_fsb) {
- del = got;
- xfs_trim_extent(&del, offset_fsb, end_fsb - offset_fsb);
-
- /* Extent delete may have bumped ext forward */
- if (!del.br_blockcount)
- goto prev_extent;
+ /*
+ * Structure copy @got into @del, then trim @del to the range that we
+ * were asked to remap. We preserve @got for the eventual CoW fork
+ * deletion; from now on @del represents the mapping that we're
+ * actually remapping.
+ */
+ del = got;
+ xfs_trim_extent(&del, offset_fsb, *end_fsb - offset_fsb);
- /*
- * Only remap real extent that contain data. With AIO
- * speculatively preallocations can leak into the range we
- * are called upon, and we need to skip them.
- */
- if (!xfs_bmap_is_real_extent(&got))
- goto prev_extent;
+ ASSERT(del.br_blockcount > 0);
- /* Unmap the old blocks in the data fork. */
- ASSERT(tp->t_firstblock == NULLFSBLOCK);
- rlen = del.br_blockcount;
- error = __xfs_bunmapi(tp, ip, del.br_startoff, &rlen, 0, 1);
- if (error)
- goto out_cancel;
+ /*
+ * Only remap real extents that contain data. With AIO, speculative
+ * preallocations can leak into the range we are called upon, and we
+ * need to skip them.
+ */
+ if (!xfs_bmap_is_real_extent(&got)) {
+ *end_fsb = del.br_startoff;
+ goto out_cancel;
+ }
- /* Trim the extent to whatever got unmapped. */
- if (rlen) {
- xfs_trim_extent(&del, del.br_startoff + rlen,
- del.br_blockcount - rlen);
- }
- trace_xfs_reflink_cow_remap(ip, &del);
+ /* Unmap the old blocks in the data fork. */
+ rlen = del.br_blockcount;
+ error = __xfs_bunmapi(tp, ip, del.br_startoff, &rlen, 0, 1);
+ if (error)
+ goto out_cancel;
- /* Free the CoW orphan record. */
- error = xfs_refcount_free_cow_extent(tp, del.br_startblock,
- del.br_blockcount);
- if (error)
- goto out_cancel;
+ /* Trim the extent to whatever got unmapped. */
+ xfs_trim_extent(&del, del.br_startoff + rlen, del.br_blockcount - rlen);
+ trace_xfs_reflink_cow_remap(ip, &del);
- /* Map the new blocks into the data fork. */
- error = xfs_bmap_map_extent(tp, ip, &del);
- if (error)
- goto out_cancel;
+ /* Free the CoW orphan record. */
+ error = xfs_refcount_free_cow_extent(tp, del.br_startblock,
+ del.br_blockcount);
+ if (error)
+ goto out_cancel;
- /* Charge this new data fork mapping to the on-disk quota. */
- xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_DELBCOUNT,
- (long)del.br_blockcount);
+ /* Map the new blocks into the data fork. */
+ error = xfs_bmap_map_extent(tp, ip, &del);
+ if (error)
+ goto out_cancel;
- /* Remove the mapping from the CoW fork. */
- xfs_bmap_del_extent_cow(ip, &icur, &got, &del);
+ /* Charge this new data fork mapping to the on-disk quota. */
+ xfs_trans_mod_dquot_byino(tp, ip, XFS_TRANS_DQ_DELBCOUNT,
+ (long)del.br_blockcount);
- error = xfs_defer_finish(&tp);
- if (error)
- goto out_cancel;
- if (!xfs_iext_get_extent(ifp, &icur, &got))
- break;
- continue;
-prev_extent:
- if (!xfs_iext_prev_extent(ifp, &icur, &got))
- break;
- }
+ /* Remove the mapping from the CoW fork. */
+ xfs_bmap_del_extent_cow(ip, &icur, &got, &del);
error = xfs_trans_commit(tp);
xfs_iunlock(ip, XFS_ILOCK_EXCL);
if (error)
- goto out;
+ return error;
+
+ /* Update the caller about how much progress we made. */
+ *end_fsb = del.br_startoff;
return 0;
out_cancel:
xfs_trans_cancel(tp);
xfs_iunlock(ip, XFS_ILOCK_EXCL);
-out:
- trace_xfs_reflink_end_cow_error(ip, error, _RET_IP_);
+ return error;
+}
+
+/*
+ * Remap parts of a file's data fork after a successful CoW.
+ */
+int
+xfs_reflink_end_cow(
+ struct xfs_inode *ip,
+ xfs_off_t offset,
+ xfs_off_t count)
+{
+ xfs_fileoff_t offset_fsb;
+ xfs_fileoff_t end_fsb;
+ int error = 0;
+
+ trace_xfs_reflink_end_cow(ip, offset, count);
+
+ offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
+ end_fsb = XFS_B_TO_FSB(ip->i_mount, offset + count);
+
+ /*
+ * Walk backwards until we're out of the I/O range. The loop function
+ * repeatedly cycles the ILOCK to allocate one transaction per remapped
+ * extent.
+ *
+ * If we're being called by writeback then the the pages will still
+ * have PageWriteback set, which prevents races with reflink remapping
+ * and truncate. Reflink remapping prevents races with writeback by
+ * taking the iolock and mmaplock before flushing the pages and
+ * remapping, which means there won't be any further writeback or page
+ * cache dirtying until the reflink completes.
+ *
+ * We should never have two threads issuing writeback for the same file
+ * region. There are also have post-eof checks in the writeback
+ * preparation code so that we don't bother writing out pages that are
+ * about to be truncated.
+ *
+ * If we're being called as part of directio write completion, the dio
+ * count is still elevated, which reflink and truncate will wait for.
+ * Reflink remapping takes the iolock and mmaplock and waits for
+ * pending dio to finish, which should prevent any directio until the
+ * remap completes. Multiple concurrent directio writes to the same
+ * region are handled by end_cow processing only occurring for the
+ * threads which succeed; the outcome of multiple overlapping direct
+ * writes is not well defined anyway.
+ *
+ * It's possible that a buffered write and a direct write could collide
+ * here (the buffered write stumbles in after the dio flushes and
+ * invalidates the page cache and immediately queues writeback), but we
+ * have never supported this 100%. If either disk write succeeds the
+ * blocks will be remapped.
+ */
+ while (end_fsb > offset_fsb && !error)
+ error = xfs_reflink_end_cow_extent(ip, offset_fsb, &end_fsb);
+
+ if (error)
+ trace_xfs_reflink_end_cow_error(ip, error, _RET_IP_);
return error;
}
projects / linux-2.6-microblaze.git / blobdiff