From 77142517990fd3d982678c2945ea2c4188ec5f9a Mon Sep 17 00:00:00 2001 From: Konstantin Khlebnikov Date: Wed, 6 Aug 2014 16:06:34 -0700 Subject: shmem: update memory reservation on truncate A shared anonymous mapping created without MAP_NORESERVE holds memory reservation for whole range of shmem segment. Usually there is no way to change its size, but /proc//map_files/... (available if CONFIG_CHECKPOINT_RESTORE=y) allows that. This patch adjusts the memory reservation in shmem_setattr(). Signed-off-by: Konstantin Khlebnikov Acked-by: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/shmem.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) (limited to 'mm/shmem.c') diff --git a/mm/shmem.c b/mm/shmem.c index 3609d31ad0dd..57fd82a5af7a 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -149,6 +149,19 @@ static inline void shmem_unacct_size(unsigned long flags, loff_t size) vm_unacct_memory(VM_ACCT(size)); } +static inline int shmem_reacct_size(unsigned long flags, + loff_t oldsize, loff_t newsize) +{ + if (!(flags & VM_NORESERVE)) { + if (VM_ACCT(newsize) > VM_ACCT(oldsize)) + return security_vm_enough_memory_mm(current->mm, + VM_ACCT(newsize) - VM_ACCT(oldsize)); + else if (VM_ACCT(newsize) < VM_ACCT(oldsize)) + vm_unacct_memory(VM_ACCT(oldsize) - VM_ACCT(newsize)); + } + return 0; +} + /* * ... whereas tmpfs objects are accounted incrementally as * pages are allocated, in order to allow huge sparse files. @@ -549,6 +562,10 @@ static int shmem_setattr(struct dentry *dentry, struct iattr *attr) loff_t newsize = attr->ia_size; if (newsize != oldsize) { + error = shmem_reacct_size(SHMEM_I(inode)->flags, + oldsize, newsize); + if (error) + return error; i_size_write(inode, newsize); inode->i_ctime = inode->i_mtime = CURRENT_TIME; } -- cgit v1.2.3-59-g8ed1b