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().

Reviewed-by: Gao Xiang <[email protected]>
Signed-off-by: Hongzhen Luo <[email protected]>
Signed-off-by: Hongbo Li <[email protected]>
---
 fs/erofs/ishare.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/fs/erofs/ishare.c b/fs/erofs/ishare.c
index da735d69f21f..d8bff0cdf702 100644
--- a/fs/erofs/ishare.c
+++ b/fs/erofs/ishare.c
@@ -230,6 +230,16 @@ 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)
+{
+       struct file *realfile = file->private_data;
+
+       if (!realfile)
+               return -EINVAL;
+       return vfs_fadvise(realfile, offset, len, advice);
+}
+
 const struct file_operations erofs_ishare_fops = {
        .open           = erofs_ishare_file_open,
        .llseek         = generic_file_llseek,
@@ -238,6 +248,7 @@ 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,
 };
 
 /*
-- 
2.22.0


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