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 This makes fstat sometimes return out-of-date block size.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>
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mm/shmem.c
16
mm/shmem.c
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@ -542,6 +542,21 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
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}
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EXPORT_SYMBOL_GPL(shmem_truncate_range);
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static int shmem_getattr(struct vfsmount *mnt, struct dentry *dentry,
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struct kstat *stat)
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{
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struct inode *inode = dentry->d_inode;
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struct shmem_inode_info *info = SHMEM_I(inode);
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spin_lock(&info->lock);
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shmem_recalc_inode(inode);
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spin_unlock(&info->lock);
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generic_fillattr(inode, stat);
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return 0;
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}
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static int shmem_setattr(struct dentry *dentry, struct iattr *attr)
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{
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struct inode *inode = d_inode(dentry);
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@ -3122,6 +3137,7 @@ static const struct file_operations shmem_file_operations = {
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};
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static const struct inode_operations shmem_inode_operations = {
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.getattr = shmem_getattr,
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.setattr = shmem_setattr,
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#ifdef CONFIG_TMPFS_XATTR
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.setxattr = shmem_setxattr,
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