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Commit 77142517 authored by Konstantin Khlebnikov's avatar Konstantin Khlebnikov Committed by Linus Torvalds
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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/<pid>/map_files/...  (available if
CONFIG_CHECKPOINT_RESTORE=y) allows that.

This patch adjusts the memory reservation in shmem_setattr().

Signed-off-by: default avatarKonstantin Khlebnikov <koct9i@gmail.com>
Acked-by: default avatarHugh Dickins <hughd@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 66ee4b88

mm/shmem.c

+17 −0
Original line number Original line Diff line number Diff line
@@ -149,6 +149,19 @@ static inline void shmem_unacct_size(unsigned long flags, loff_t size) 
		vm_unacct_memory(VM_ACCT(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

 * ... whereas tmpfs objects are accounted incrementally as

 * pages are allocated, in order to allow huge sparse files.

 * 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;

		loff_t newsize = attr->ia_size;





		if (newsize != oldsize) {

		if (newsize != oldsize) {

			error = shmem_reacct_size(SHMEM_I(inode)->flags,

					oldsize, newsize);

			if (error)

				return error;

			i_size_write(inode, newsize);

			i_size_write(inode, newsize);

			inode->i_ctime = inode->i_mtime = CURRENT_TIME;

			inode->i_ctime = inode->i_mtime = CURRENT_TIME;

		}

		}