From: Hongzhen Luo <[email protected]>

This patch implements the .fadvise interface for page cache share.
Similar to overlayfs, it drops those clean, unused pages through
vfs_fadvise().

Signed-off-by: Hongzhen Luo <[email protected]>
Signed-off-by: Hongbo Li <[email protected]>
Reviewed-by: Gao Xiang <[email protected]>
---
 fs/erofs/ishare.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/erofs/ishare.c b/fs/erofs/ishare.c
index ad53a57dbcbc..ce980320a8b9 100644
--- a/fs/erofs/ishare.c
+++ b/fs/erofs/ishare.c
@@ -151,6 +151,12 @@ static int erofs_ishare_mmap(struct file *file, struct 
vm_area_struct *vma)
        return generic_file_readonly_mmap(file, vma);
 }
 
+static int erofs_ishare_fadvise(struct file *file, loff_t offset,
+                               loff_t len, int advice)
+{
+       return vfs_fadvise(file->private_data, offset, len, advice);
+}
+
 const struct file_operations erofs_ishare_fops = {
        .open           = erofs_ishare_file_open,
        .llseek         = generic_file_llseek,
@@ -159,6 +165,7 @@ const struct file_operations erofs_ishare_fops = {
        .release        = erofs_ishare_file_release,
        .get_unmapped_area = thp_get_unmapped_area,
        .splice_read    = filemap_splice_read,
+       .fadvise        = erofs_ishare_fadvise,
 };
 
 struct inode *erofs_real_inode(struct inode *inode, bool *need_iput)
-- 
2.22.0


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