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Subject[PATCH 6/7] shmem: rework majmin and ZERO_PAGE
Very minor adjustments to shmem_getpage return path: I now prefer it to
return NULL and let do_shmem_file_read use ZERO_PAGE(0) in that case;
and we don't need a local majmin variable, do_no_page initializes *type
to VM_FAULT_MINOR already.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
---
mm/shmem.c | 26 ++++++++++++--------------
1 files changed, 12 insertions(+), 14 deletions(-)
--- shmem5/mm/shmem.c 2004-09-05 17:06:30.195820472 +0100
+++ shmem6/mm/shmem.c 2004-09-05 17:06:41.258138744 +0100
@@ -885,7 +885,7 @@ static int shmem_getpage(struct inode *i
struct page *swappage;
swp_entry_t *entry;
swp_entry_t swap;
- int error, majmin = VM_FAULT_MINOR;
+ int error;

if (idx >= SHMEM_MAX_INDEX)
return -EFBIG;
@@ -923,9 +923,10 @@ repeat:
shmem_swp_unmap(entry);
spin_unlock(&info->lock);
/* here we actually do the io */
- if (majmin == VM_FAULT_MINOR && type)
+ if (type && *type == VM_FAULT_MINOR) {
inc_page_state(pgmajfault);
- majmin = VM_FAULT_MAJOR;
+ *type = VM_FAULT_MAJOR;
+ }
swappage = shmem_swapin(info, swap, idx);
if (!swappage) {
spin_lock(&info->lock);
@@ -1077,15 +1078,10 @@ repeat:
SetPageUptodate(filepage);
}
done:
- if (!*pagep) {
- if (filepage) {
- unlock_page(filepage);
- *pagep = filepage;
- } else
- *pagep = ZERO_PAGE(0);
+ if (*pagep != filepage) {
+ unlock_page(filepage);
+ *pagep = filepage;
}
- if (type)
- *type = majmin;
return 0;

failed:
@@ -1442,13 +1438,14 @@ static void do_shmem_file_read(struct fi
if (index == end_index) {
nr = i_size & ~PAGE_CACHE_MASK;
if (nr <= offset) {
- page_cache_release(page);
+ if (page)
+ page_cache_release(page);
break;
}
}
nr -= offset;

- if (page != ZERO_PAGE(0)) {
+ if (page) {
/*
* If users can be writing to this page using arbitrary
* virtual addresses, take care about potential aliasing
@@ -1461,7 +1458,8 @@ static void do_shmem_file_read(struct fi
*/
if (!offset)
mark_page_accessed(page);
- }
+ } else
+ page = ZERO_PAGE(0);

/*
* Ok, we have the page, and it's up-to-date, so
-
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