[Linux-cachefs] [PATCH] FS-Cache: Fix __fscache_uncache_all_inode_pages()'s outer loop

[David Howells]

From: Jan Beulich <JBeulich at novell.com>

The compiler, at least for ix86 and m68k, validly warns that the comparison:

	next <= (loff_t)-1

is always true (and it's always true also for x86-64 and probably all other
arches - as long as pgoff_t isn't wider than loff_t).  The intention appears
to be to avoid wrapping of "next", so rather than eliminating the pointless
comparison, fix the loop to indeed get exited when "next" would otherwise
wrap.

On m68k the following warning is observed:

fs/fscache/page.c: In function '__fscache_uncache_all_inode_pages':
fs/fscache/page.c:979: warning: comparison is always false due to
limited range of data type

Reported-by: Geert Uytterhoeven <geert at linux-m68k.org>
Reported-by: Jan Beulich <jbeulich at novell.com>
Signed-off-by: Jan Beulich <jbeulich at novell.com>
Signed-off-by: David Howells <dhowells at redhat.com>
Cc: Suresh Jayaraman <sjayaraman at suse.de>
Cc: Geert Uytterhoeven <geert at linux-m68k.org>
Cc: stable at kernel.org
---

 fs/fscache/page.c |   14 +++++---------
 1 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/fs/fscache/page.c b/fs/fscache/page.c
index 60315b3..ff1e68f 100644
--- a/fs/fscache/page.c
+++ b/fs/fscache/page.c
@@ -993,16 +993,12 @@ void __fscache_uncache_all_inode_pages(struct fscache_cookie *cookie,
 
 	pagevec_init(&pvec, 0);
 	next = 0;
-	while (next <= (loff_t)-1 &&
-	       pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)
-	       ) {
+	do {
+		if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE))
+			break;
 		for (i = 0; i < pagevec_count(&pvec); i++) {
 			struct page *page = pvec.pages[i];
-			pgoff_t page_index = page->index;
-
-			ASSERTCMP(page_index, >=, next);
-			next = page_index + 1;
-
+			next = page->index;
 			if (PageFsCache(page)) {
 				__fscache_wait_on_page_write(cookie, page);
 				__fscache_uncache_page(cookie, page);
@@ -1010,7 +1006,7 @@ void __fscache_uncache_all_inode_pages(struct fscache_cookie *cookie,
 		}
 		pagevec_release(&pvec);
 		cond_resched();
-	}
+	} while (++next);
 
 	_leave("");
 }