Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=16a100190d39592d1d56ff5a0b978b20288c3427
Commit: 16a100190d39592d1d56ff5a0b978b20288c3427
Parent: 1ae7000630e3c05b6f7e3dfc76472f1bca6c1788
Author: Hugh Dickins <[EMAIL PROTECTED]>
AuthorDate: Thu Mar 29 01:20:37 2007 -0700
Committer: Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Thu Mar 29 08:22:25 2007 -0700
[PATCH] holepunch: fix disconnected pages after second truncate
shmem_truncate_range has its own truncate_inode_pages_range, to free any
pages
racily instantiated while it was in progress: a SHMEM_PAGEIN flag is set
when
this might have happened. But holepunching gets no chance to clear that
flag
at the start of vmtruncate_range, so it's always set (unless a truncate came
just before), so holepunch almost always does this second
truncate_inode_pages_range.
shmem holepunch has unlikely swap<->file races hereabouts whatever we do
(without a fuller rework than is fit for this release): I was going to skip
the second truncate in the punch_hole case, but Miklos points out that would
make holepunch correctness more vulnerable to swapoff. So keep the second
truncate, but follow it by an unmap_mapping_range to eliminate the
disconnected pages (freed from pagecache while still mapped in userspace)
that
it might have left behind.
Signed-off-by: Hugh Dickins <[EMAIL PROTECTED]>
Cc: Miklos Szeredi <[EMAIL PROTECTED]>
Cc: Badari Pulavarty <[EMAIL PROTECTED]>
Cc: Nick Piggin <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
mm/shmem.c | 8 ++++++++
1 files changed, 8 insertions(+), 0 deletions(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index 578ecea..b2a35eb 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -674,8 +674,16 @@ done2:
* generic_delete_inode did it, before we lowered next_index.
* Also, though shmem_getpage checks i_size before adding to
* cache, no recheck after: so fix the narrow window there too.
+ *
+ * Recalling truncate_inode_pages_range and unmap_mapping_range
+ * every time for punch_hole (which never got a chance to clear
+ * SHMEM_PAGEIN at the start of vmtruncate_range) is expensive,
+ * yet hardly ever necessary: try to optimize them out later.
*/
truncate_inode_pages_range(inode->i_mapping, start, end);
+ if (punch_hole)
+ unmap_mapping_range(inode->i_mapping, start,
+ end - start, 1);
}
spin_lock(&info->lock);
-
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