coda: add hinting support for partial file caching

This adds support for partial file caching in Coda.  Every read, write
and mmap informs the userspace cache manager about what part of a file
is about to be accessed so that the cache manager can ensure the
relevant parts are available before the operation is allowed to proceed.

When a read or write operation completes, this is also reported to allow
the cache manager to track when partially cached content can be
released.

If the cache manager does not support partial file caching, or when the
entire file has been fetched into the local cache, the cache manager may
return an EOPNOTSUPP error to indicate that intent upcalls are no longer
necessary until the file is closed.

[akpm@linux-foundation.org: little whitespace fixup]
Link: http://lkml.kernel.org/r/20190618181301.6960-1-jaharkes@cs.cmu.edu
Signed-off-by: Pedro Cuadra <pjcuadra@gmail.com>
Signed-off-by: Jan Harkes <jaharkes@cs.cmu.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 49 insertions, 12 deletions

diff --git a/fs/coda/file.c b/fs/coda/file.c
index 0dbd13ab72e3..128d63df5bfb 100644
--- a/fs/coda/file.c
+++ b/fs/coda/file.c
@@ -20,6 +20,7 @@
 #include <linux/string.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
+#include <linux/uio.h>
 
 #include <linux/coda.h>
 #include "coda_psdev.h"
@@ -37,9 +38,25 @@ static ssize_t
 coda_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
 {
         struct file *coda_file = iocb->ki_filp;
+        struct inode *coda_inode = file_inode(coda_file);
         struct coda_file_info *cfi = coda_ftoc(coda_file);
+        loff_t ki_pos = iocb->ki_pos;
+        size_t count = iov_iter_count(to);
+        ssize_t ret;
+
+        ret = venus_access_intent(coda_inode->i_sb, coda_i2f(coda_inode),
+                                  &cfi->cfi_access_intent,
+                                  count, ki_pos, CODA_ACCESS_TYPE_READ);
+        if (ret)
+                goto finish_read;
 
-        return vfs_iter_read(cfi->cfi_container, to, &iocb->ki_pos, 0);
+        ret = vfs_iter_read(cfi->cfi_container, to, &iocb->ki_pos, 0);
+
+finish_read:
+        venus_access_intent(coda_inode->i_sb, coda_i2f(coda_inode),
+                            &cfi->cfi_access_intent,
+                            count, ki_pos, CODA_ACCESS_TYPE_READ_FINISH);
+        return ret;
 }
 
 static ssize_t
@@ -48,10 +65,17 @@ coda_file_write_iter(struct kiocb *iocb, struct iov_iter *to)
         struct file *coda_file = iocb->ki_filp;
         struct inode *coda_inode = file_inode(coda_file);
         struct coda_file_info *cfi = coda_ftoc(coda_file);
-        struct file *host_file;
+        struct file *host_file = cfi->cfi_container;
+        loff_t ki_pos = iocb->ki_pos;
+        size_t count = iov_iter_count(to);
         ssize_t ret;
 
-        host_file = cfi->cfi_container;
+        ret = venus_access_intent(coda_inode->i_sb, coda_i2f(coda_inode),
+                                  &cfi->cfi_access_intent,
+                                  count, ki_pos, CODA_ACCESS_TYPE_WRITE);
+        if (ret)
+                goto finish_write;
+
         file_start_write(host_file);
         inode_lock(coda_inode);
         ret = vfs_iter_write(cfi->cfi_container, to, &iocb->ki_pos, 0);
@@ -60,6 +84,11 @@ coda_file_write_iter(struct kiocb *iocb, struct iov_iter *to)
         coda_inode->i_mtime = coda_inode->i_ctime = current_time(coda_inode);
         inode_unlock(coda_inode);
         file_end_write(host_file);
+
+finish_write:
+        venus_access_intent(coda_inode->i_sb, coda_i2f(coda_inode),
+                            &cfi->cfi_access_intent,
+                            count, ki_pos, CODA_ACCESS_TYPE_WRITE_FINISH);
         return ret;
 }
 
@@ -94,29 +123,35 @@ coda_vm_close(struct vm_area_struct *vma)
 static int
 coda_file_mmap(struct file *coda_file, struct vm_area_struct *vma)
 {
-        struct coda_file_info *cfi;
+        struct inode *coda_inode = file_inode(coda_file);
+        struct coda_file_info *cfi = coda_ftoc(coda_file);
+        struct file *host_file = cfi->cfi_container;
+        struct inode *host_inode = file_inode(host_file);
         struct coda_inode_info *cii;
-        struct file *host_file;
-        struct inode *coda_inode, *host_inode;
         struct coda_vm_ops *cvm_ops;
+        loff_t ppos;
+        size_t count;
         int ret;
 
-        cfi = coda_ftoc(coda_file);
-        host_file = cfi->cfi_container;
-
         if (!host_file->f_op->mmap)
                 return -ENODEV;
 
         if (WARN_ON(coda_file != vma->vm_file))
                 return -EIO;
 
+        count = vma->vm_end - vma->vm_start;
+        ppos = vma->vm_pgoff * PAGE_SIZE;
+
+        ret = venus_access_intent(coda_inode->i_sb, coda_i2f(coda_inode),
+                                  &cfi->cfi_access_intent,
+                                  count, ppos, CODA_ACCESS_TYPE_MMAP);
+        if (ret)
+                return ret;
+
         cvm_ops = kmalloc(sizeof(struct coda_vm_ops), GFP_KERNEL);
         if (!cvm_ops)
                 return -ENOMEM;
 
-        coda_inode = file_inode(coda_file);
-        host_inode = file_inode(host_file);
-
         cii = ITOC(coda_inode);
         spin_lock(&cii->c_lock);
         coda_file->f_mapping = host_file->f_mapping;
@@ -188,6 +223,8 @@ int coda_open(struct inode *coda_inode, struct file *coda_file)
         cfi->cfi_magic = CODA_MAGIC;
         cfi->cfi_mapcount = 0;
         cfi->cfi_container = host_file;
+        /* assume access intents are supported unless we hear otherwise */
+        cfi->cfi_access_intent = true;
 
         BUG_ON(coda_file->private_data != NULL);
         coda_file->private_data = cfi;