[patch 13/41] mm: restore KERNEL_DS optimisations
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STALE7084d
From: <hidden>
Date: 2007-05-14 08:23:55
Also in:
linux-fsdevel
Restore the KERNEL_DS optimisation, especially helpful to the 2copy write path. This may be a pretty questionable gain in most cases, especially after the legacy 2copy write path is removed, but it doesn't cost much. Cc: Linux Memory Management <redacted> Cc: Linux Filesystems <redacted> Signed-off-by: Nick Piggin <redacted> mm/filemap.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) Index: linux-2.6/mm/filemap.c ===================================================================
--- linux-2.6.orig/mm/filemap.c
+++ linux-2.6/mm/filemap.c@@ -2113,7 +2113,7 @@ static ssize_t generic_perform_write_2co * cannot take a pagefault with the destination page locked. * So pin the source page to copy it. */ - if (!PageUptodate(page)) { + if (!PageUptodate(page) && !segment_eq(get_fs(), KERNEL_DS)) { unlock_page(page); src_page = alloc_page(GFP_KERNEL);
@@ -2238,6 +2238,13 @@ static ssize_t generic_perform_write(str const struct address_space_operations *a_ops = mapping->a_ops; long status = 0; ssize_t written = 0; + unsigned int flags = 0; + + /* + * Copies from kernel address space cannot fail (NFSD is a big user). + */ + if (segment_eq(get_fs(), KERNEL_DS)) + flags |= AOP_FLAG_UNINTERRUPTIBLE; do { struct page *page;
@@ -2269,7 +2276,7 @@ again: break; } - status = a_ops->write_begin(file, mapping, pos, bytes, 0, + status = a_ops->write_begin(file, mapping, pos, bytes, flags, &page, &fsdata); if (unlikely(status)) break;
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