xnu-3789.70.16.tar.gz

[apple/xnu.git] / bsd / vfs / vfs_cluster.c

diff --git a/bsd/vfs/vfs_cluster.c b/bsd/vfs/vfs_cluster.c
index d6b22ff84909a39c05b048607d93c4e4bc3468e6..70eecc5ff44759d87818dc61b6ea475697195ea0 100644 (file)
--- a/bsd/vfs/vfs_cluster.c
+++ b/bsd/vfs/vfs_cluster.c
@@ -1360,47 +1360,69 @@ cluster_io(vnode_t vp, upl_t upl, vm_offset_t upl_offset, off_t f_offset, int no
                                pageout_flags |= UPL_NOCOMMIT;
 
                        if (cbp_head) {
-                               buf_t last_cbp;
+                               buf_t prev_cbp;
+                               int   bytes_in_last_page;
 
                                /*
                                 * first we have to wait for the the current outstanding I/Os
                                 * to complete... EOT hasn't been set yet on this transaction
-                                * so the pages won't be released just because all of the current
-                                * I/O linked to this transaction has completed...
+                                * so the pages won't be released
                                 */
                                cluster_wait_IO(cbp_head, (flags & CL_ASYNC));
 
-                               /*
-                                * we've got a transcation that
-                                * includes the page we're about to push out through vnode_pageout...
-                                * find the last bp in the list which will be the one that
-                                * includes the head of this page and round it's iosize down
-                                * to a page boundary...
-                                */
-                                for (last_cbp = cbp = cbp_head; cbp->b_trans_next; cbp = cbp->b_trans_next)
-                                       last_cbp = cbp;
-
-                               cbp->b_bcount &= ~PAGE_MASK;
-
-                               if (cbp->b_bcount == 0) {
-                                       /*
-                                        * this buf no longer has any I/O associated with it
+                               bytes_in_last_page = cbp_head->b_uploffset & PAGE_MASK;
+                               for (cbp = cbp_head; cbp; cbp = cbp->b_trans_next)
+                                       bytes_in_last_page += cbp->b_bcount;
+                               bytes_in_last_page &= PAGE_MASK;
+                               
+                               while (bytes_in_last_page) {
+                                       /*
+                                        * we've got a transcation that
+                                        * includes the page we're about to push out through vnode_pageout...
+                                        * find the bp's in the list which intersect this page and either
+                                        * remove them entirely from the transaction (there could be multiple bp's), or
+                                        * round it's iosize down to the page boundary (there can only be one)...
+                                        *
+                                        * find the last bp in the list and act on it
                                         */
-                                       free_io_buf(cbp);
+                                       for (prev_cbp = cbp = cbp_head; cbp->b_trans_next; cbp = cbp->b_trans_next)
+                                               prev_cbp = cbp;
 
-                                       if (cbp == cbp_head) {
-                                               /*
-                                                * the buf we just freed was the only buf in
-                                                * this transaction... so there's no I/O to do
+                                       if (bytes_in_last_page >= cbp->b_bcount) {
+                                               /*
+                                                * this buf no longer has any I/O associated with it
                                                 */
-                                               cbp_head = NULL;
+                                               bytes_in_last_page -= cbp->b_bcount;
+                                               cbp->b_bcount = 0;
+
+                                               free_io_buf(cbp);
+
+                                               if (cbp == cbp_head) {
+                                                       assert(bytes_in_last_page == 0);
+                                                       /*
+                                                        * the buf we just freed was the only buf in
+                                                        * this transaction... so there's no I/O to do
+                                                        */
+                                                       cbp_head = NULL;
+                                                       cbp_tail = NULL;
+                                               } else {
+                                                       /*
+                                                        * remove the buf we just freed from
+                                                        * the transaction list
+                                                        */
+                                                       prev_cbp->b_trans_next = NULL;
+                                                       cbp_tail = prev_cbp;
+                                               }
                                        } else {
-                                               /*
-                                                * remove the buf we just freed from
-                                                * the transaction list
+                                               /*
+                                                * this is the last bp that has I/O
+                                                * intersecting the page of interest
+                                                * only some of the I/O is in the intersection
+                                                * so clip the size but keep it in the transaction list
                                                 */
-                                               last_cbp->b_trans_next = NULL;
-                                               cbp_tail = last_cbp;
+                                               cbp->b_bcount -= bytes_in_last_page;
+                                               cbp_tail = cbp;
+                                               bytes_in_last_page = 0;
                                        }
                                }
                                if (cbp_head) {