From d44ed4f86892e350f4b16a3489b7e7c1a9bb7ead Mon Sep 17 00:00:00 2001
From: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Date: Sat, 3 Sep 2005 15:54:55 -0700
Subject: [PATCH] [PATCH] shmem_populate: avoid an useless check, and some
comments
Either shmem_getpage returns a failure, or it found a page, or it was told
it couldn't do any I/O. So it's useless to check nonblock in the else
branch. We could add a BUG() there but I preferred to comment the
offending function.
This was taken out from one Ingo Molnar's old patch I'm resurrecting.
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
mm/filemap.c | 7 +++++++
mm/shmem.c | 6 +++++-
2 files changed, 12 insertions(+), 1 deletion(-)
diff --git a/mm/filemap.c b/mm/filemap.c
index edc54436fa94..88611928e71f 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1504,8 +1504,12 @@ repeat:
return -EINVAL;
page = filemap_getpage(file, pgoff, nonblock);
+
+ /* XXX: This is wrong, a filesystem I/O error may have happened. Fix that as
+ * done in shmem_populate calling shmem_getpage */
if (!page && !nonblock)
return -ENOMEM;
+
if (page) {
err = install_page(mm, vma, addr, page, prot);
if (err) {
@@ -1513,6 +1517,9 @@ repeat:
return err;
}
} else {
+ /* No page was found just because we can't read it in now (being
+ * here implies nonblock != 0), but the page may exist, so set
+ * the PTE to fault it in later. */
err = install_file_pte(mm, vma, addr, pgoff, prot);
if (err)
return err;
diff --git a/mm/shmem.c b/mm/shmem.c
index 5a81b1ee4f7a..08a3bc2fba61 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1195,6 +1195,7 @@ static int shmem_populate(struct vm_area_struct *vma,
err = shmem_getpage(inode, pgoff, &page, sgp, NULL);
if (err)
return err;
+ /* Page may still be null, but only if nonblock was set. */
if (page) {
mark_page_accessed(page);
err = install_page(mm, vma, addr, page, prot);
@@ -1202,7 +1203,10 @@ static int shmem_populate(struct vm_area_struct *vma,
page_cache_release(page);
return err;
}
- } else if (nonblock) {
+ } else {
+ /* No page was found just because we can't read it in
+ * now (being here implies nonblock != 0), but the page
+ * may exist, so set the PTE to fault it in later. */
err = install_file_pte(mm, vma, addr, pgoff, prot);
if (err)
return err;