4.9-stable review patch. If anyone has any objections, please let me know.
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From: Arnd Bergmann arnd@arndb.de
commit 23f919d4ad0eb325595f10f55be4301b2965d6d6 upstream.
After enabling -Wmaybe-uninitialized warnings, we get a false-postive warning for shmem:
mm/shmem.c: In function `shmem_getpage_gfp': include/linux/spinlock.h:332:21: error: `info' may be used uninitialized in this function [-Werror=maybe-uninitialized]
This can be easily avoided, since the correct 'info' pointer is known at the time we first enter the function, so we can simply move the initialization up. Moving it before the first label avoids the warning and lets us remove two later initializations.
Note that the function is so hard to read that it not only confuses the compiler, but also most readers and without this patch it could\ easily break if one of the 'goto's changed.
Link: https://www.spinics.net/lists/kernel/msg2368133.html Link: http://lkml.kernel.org/r/20161024205725.786455-1-arnd@arndb.de Signed-off-by: Arnd Bergmann arnd@arndb.de Acked-by: Michal Hocko mhocko@suse.com Acked-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Acked-by: Vlastimil Babka vbabka@suse.cz Cc: Hugh Dickins hughd@google.com Cc: Andreas Gruenbacher agruenba@redhat.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- mm/shmem.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)
--- a/mm/shmem.c +++ b/mm/shmem.c @@ -1550,7 +1550,7 @@ static int shmem_getpage_gfp(struct inod struct mm_struct *fault_mm, int *fault_type) { struct address_space *mapping = inode->i_mapping; - struct shmem_inode_info *info; + struct shmem_inode_info *info = SHMEM_I(inode); struct shmem_sb_info *sbinfo; struct mm_struct *charge_mm; struct mem_cgroup *memcg; @@ -1600,7 +1600,6 @@ repeat: * Fast cache lookup did not find it: * bring it back from swap or allocate. */ - info = SHMEM_I(inode); sbinfo = SHMEM_SB(inode->i_sb); charge_mm = fault_mm ? : current->mm;
@@ -1852,7 +1851,6 @@ unlock: put_page(page); } if (error == -ENOSPC && !once++) { - info = SHMEM_I(inode); spin_lock_irq(&info->lock); shmem_recalc_inode(inode); spin_unlock_irq(&info->lock);