Shared anon mappings created without MAP_NORESERVE may hold reservation of
memory commitment for whole size of shmem segment. There was no way to change
that size, but recently introduced 'map_files' in proc allows to do that.
This patch adjust memory reservation in shmem_setattr() during truncating.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxx>
---
mm/shmem.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/mm/shmem.c b/mm/shmem.c
index ff08920..a15c8dd 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -148,6 +148,19 @@ 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.
@@ -607,6 +620,10 @@ 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;
}
--
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