The patch titled
generic_file_buffered_write(): deadlock on vectored write
has been removed from the -mm tree. Its filename is
generic_file_buffered_write-deadlock-on-vectored-write.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
Subject: generic_file_buffered_write(): deadlock on vectored write
From: "Vladimir V. Saveliev" <vs@xxxxxxxxxxx>
generic_file_buffered_write() prefaults in user pages in order to avoid
deadlock on copying from the same page as write goes to.
However, it looks like there is a problem when write is vectored:
fault_in_pages_readable brings in current segment or its part (maxlen).
OTOH, filemap_copy_from_user_iovec is called to copy number of bytes
(bytes) which may exceed current segment, so filemap_copy_from_user_iovec
switches to the next segment which is not brought in yet. Pagefault is
generated. That causes the deadlock if pagefault is for the same page
write goes to: page being written is locked and not uptodate, pagefault
will deadlock trying to lock locked page.
[akpm@xxxxxxxx: somewhat rewritten]
Cc: Neil Brown <neilb@xxxxxxx>
Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
mm/filemap.c | 18 +++++++++++-------
1 file changed, 11 insertions(+), 7 deletions(-)
diff -puN mm/filemap.c~generic_file_buffered_write-deadlock-on-vectored-write mm/filemap.c
--- a/mm/filemap.c~generic_file_buffered_write-deadlock-on-vectored-write
+++ a/mm/filemap.c
@@ -2095,14 +2095,21 @@ generic_file_buffered_write(struct kiocb
do {
unsigned long index;
unsigned long offset;
- unsigned long maxlen;
size_t copied;
offset = (pos & (PAGE_CACHE_SIZE -1)); /* Within page */
index = pos >> PAGE_CACHE_SHIFT;
bytes = PAGE_CACHE_SIZE - offset;
- if (bytes > count)
- bytes = count;
+
+ /* Limit the size of the copy to the caller's write size */
+ bytes = min(bytes, count);
+
+ /*
+ * Limit the size of the copy to that of the current segment,
+ * because fault_in_pages_readable() doesn't know how to walk
+ * segments.
+ */
+ bytes = min(bytes, cur_iov->iov_len - iov_base);
/*
* Bring in the user page that we will copy from _first_.
@@ -2110,10 +2117,7 @@ generic_file_buffered_write(struct kiocb
* same page as we're writing to, without it being marked
* up-to-date.
*/
- maxlen = cur_iov->iov_len - iov_base;
- if (maxlen > bytes)
- maxlen = bytes;
- fault_in_pages_readable(buf, maxlen);
+ fault_in_pages_readable(buf, bytes);
page = __grab_cache_page(mapping,index,&cached_page,&lru_pvec);
if (!page) {
_
Patches currently in -mm which might be from vs@xxxxxxxxxxx are
origin.patch
reiser4.patch
reiser4-hardirq-include-fix.patch
reiser4-fix-trivial-tyops-which-were-hard-to-hit.patch
reiser4-run-truncate_inode_pages-in-reiser4_delete_inode.patch
fs-reiser4-possible-cleanups.patch
reiser4-get_sb_dev-fix.patch
reiser4-vs-zoned-allocator.patch
-
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