From: Eric Dumazet on
Le lundi 05 avril 2010 à 23:04 +0200, Eric Dumazet a écrit :
> Andrew, commit dcefafb6ac90ece8d68a6c203105f3d313e52da4 seems to be the
> problem.
> It breaks rewinds (negative offsets to lseek (... SEEK_CUR))

Here is a patch to make rewind working again on /dev/mem

[PATCH] /dev/mem: Allow rewinding

commit dcefafb6 (/dev/mem: dont allow seek to last page)
inadvertently disabled rewinding on /dev/mem.

This broke x86info for example.

Signed-off-by: Eric Dumazet <eric.dumazet(a)>
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 1f3215a..3973a1d 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -710,11 +710,6 @@ static loff_t memory_lseek(struct file *file, loff_t offset, int orig)
switch (orig) {
case SEEK_CUR:
offset += file->f_pos;
- if ((unsigned long long)offset <
- (unsigned long long)file->f_pos) {
- ret = -EOVERFLOW;
- break;
- }
case SEEK_SET:
/* to avoid userland mistaking f_pos=-9 as -EBADF=-9 */
if ((unsigned long long)offset >= ~0xFFFULL) {

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