Commit 44a30220 authored Sep 08, 2015 by Yu Zhao Committed by Linus Torvalds Sep 08, 2015

shmem: recalculate file inode when fstat



Shmem uses shmem_recalc_inode to update i_blocks when it allocates page,
undoes range or swaps.  But mm can drop clean page without notifying
shmem.  This makes fstat sometimes return out-of-date block size.

The problem can be partially solved when we add
inode_operations->getattr which calls shmem_recalc_inode to update
i_blocks for fstat.

shmem_recalc_inode also updates counter used by statfs and
vm_committed_as.  For them the situation is not changed.  They still
suffer from the discrepancy after dropping clean page and before the
function is called by aforementioned triggers.

Signed-off-by: Yu Zhao <yuzhao@google.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 567d117b

mm/shmem.c

+16 −0

Original line number	Diff line number	Diff line
		@@ -542,6 +542,21 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
		}
		EXPORT_SYMBOL_GPL(shmem_truncate_range);

		static int shmem_getattr(struct vfsmount mnt, struct dentry dentry,
		struct kstat *stat)
		{
		struct inode *inode = dentry->d_inode;
		struct shmem_inode_info *info = SHMEM_I(inode);

		spin_lock(&info->lock);
		shmem_recalc_inode(inode);
		spin_unlock(&info->lock);

		generic_fillattr(inode, stat);

		return 0;
		}

		static int shmem_setattr(struct dentry dentry, struct iattr attr)
		{
		struct inode *inode = d_inode(dentry);
		@@ -3122,6 +3137,7 @@ static const struct file_operations shmem_file_operations = {
		};

		static const struct inode_operations shmem_inode_operations = {
		.getattr = shmem_getattr,
		.setattr = shmem_setattr,
		#ifdef CONFIG_TMPFS_XATTR
		.setxattr = shmem_setxattr,