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| author | Nick Piggin <npiggin@suse.de> | 2007-10-16 01:25:03 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-10-16 09:42:55 -0700 |
| commit | 674b892ede247ef4fb8d00918f02e29c32b9bbaf (patch) | |
| tree | 8e170040e64073932ba559cc31f3ec9802337406 /mm | |
| parent | 8268f5a7415d914fc855a86aa2284ac819dc6b2e (diff) | |
| download | lwn-674b892ede247ef4fb8d00918f02e29c32b9bbaf.tar.gz lwn-674b892ede247ef4fb8d00918f02e29c32b9bbaf.zip | |
mm: restore KERNEL_DS optimisations
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.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/filemap.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/mm/filemap.c b/mm/filemap.c index ec25ba1aef5f..ca04226bf1de 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2061,7 +2061,7 @@ static ssize_t generic_perform_write_2copy(struct file *file, * 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); @@ -2186,6 +2186,13 @@ static ssize_t generic_perform_write(struct file *file, 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; @@ -2217,7 +2224,7 @@ 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; |