NFS: Add comment banners to some NFS functions

[mirror_ubuntu-jammy-kernel.git] / fs / nfs / file.c

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 90f292b520d25eec248a9728b7d61cf20cd061f9..f5bc54dccecbf6746dc2200b04baea5d27b8cfac 100644 (file)
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -64,11 +64,7 @@ const struct file_operations nfs_file_operations = {
        .write          = do_sync_write,
        .aio_read       = nfs_file_read,
        .aio_write      = nfs_file_write,
-#ifdef CONFIG_MMU
        .mmap           = nfs_file_mmap,
-#else
-       .mmap           = generic_file_mmap,
-#endif
        .open           = nfs_file_open,
        .flush          = nfs_file_flush,
        .release        = nfs_file_release,
@@ -141,9 +137,6 @@ nfs_file_release(struct inode *inode, struct file *filp)
                        dentry->d_parent->d_name.name,
                        dentry->d_name.name);
 
-       /* Ensure that dirty pages are flushed out with the right creds */
-       if (filp->f_mode & FMODE_WRITE)
-               nfs_wb_all(dentry->d_inode);
        nfs_inc_stats(inode, NFSIOS_VFSRELEASE);
        return nfs_release(inode, filp);
 }
@@ -235,7 +228,6 @@ nfs_file_flush(struct file *file, fl_owner_t id)
        struct nfs_open_context *ctx = nfs_file_open_context(file);
        struct dentry   *dentry = file->f_path.dentry;
        struct inode    *inode = dentry->d_inode;
-       int             status;
 
        dprintk("NFS: flush(%s/%s)\n",
                        dentry->d_parent->d_name.name,
@@ -245,11 +237,8 @@ nfs_file_flush(struct file *file, fl_owner_t id)
                return 0;
        nfs_inc_stats(inode, NFSIOS_VFSFLUSH);
 
-       /* Ensure that data+attribute caches are up to date after close() */
-       status = nfs_do_fsync(ctx, inode);
-       if (!status)
-               nfs_revalidate_inode(NFS_SERVER(inode), inode);
-       return status;
+       /* Flush writes to the server and return any errors */
+       return nfs_do_fsync(ctx, inode);
 }
 
 static ssize_t
@@ -304,11 +293,13 @@ nfs_file_mmap(struct file * file, struct vm_area_struct * vma)
        dprintk("NFS: mmap(%s/%s)\n",
                dentry->d_parent->d_name.name, dentry->d_name.name);
 
-       status = nfs_revalidate_mapping(inode, file->f_mapping);
+       /* Note: generic_file_mmap() returns ENOSYS on nommu systems
+        *       so we call that before revalidating the mapping
+        */
+       status = generic_file_mmap(file, vma);
        if (!status) {
                vma->vm_ops = &nfs_file_vm_ops;
-               vma->vm_flags |= VM_CAN_NONLINEAR;
-               file_accessed(file);
+               status = nfs_revalidate_mapping(inode, file->f_mapping);
        }
        return status;
 }
@@ -354,6 +345,15 @@ static int nfs_write_begin(struct file *file, struct address_space *mapping,
                file->f_path.dentry->d_name.name,
                mapping->host->i_ino, len, (long long) pos);
 
+       /*
+        * Prevent starvation issues if someone is doing a consistency
+        * sync-to-disk
+        */
+       ret = wait_on_bit(&NFS_I(mapping->host)->flags, NFS_INO_FLUSHING,
+                       nfs_wait_bit_killable, TASK_KILLABLE);
+       if (ret)
+               return ret;
+
        page = grab_cache_page_write_begin(mapping, index, flags);
        if (!page)
                return -ENOMEM;
@@ -409,6 +409,13 @@ static int nfs_write_end(struct file *file, struct address_space *mapping,
        return copied;
 }
 
+/*
+ * Partially or wholly invalidate a page
+ * - Release the private state associated with a page if undergoing complete
+ *   page invalidation
+ * - Called if either PG_private or PG_private_2 is set on the page
+ * - Caller holds page lock
+ */
 static void nfs_invalidate_page(struct page *page, unsigned long offset)
 {
        dfprintk(PAGECACHE, "NFS: invalidate_page(%p, %lu)\n", page, offset);
@@ -419,6 +426,12 @@ static void nfs_invalidate_page(struct page *page, unsigned long offset)
        nfs_wb_page_cancel(page->mapping->host, page);
 }
 
+/*
+ * Attempt to release the private state associated with a page
+ * - Called if either PG_private or PG_private_2 is set on the page
+ * - Caller holds page lock
+ * - Return true (may release page) or false (may not)
+ */
 static int nfs_release_page(struct page *page, gfp_t gfp)
 {
        dfprintk(PAGECACHE, "NFS: release_page(%p)\n", page);
@@ -427,6 +440,14 @@ static int nfs_release_page(struct page *page, gfp_t gfp)
        return 0;
 }
 
+/*
+ * Attempt to clear the private state associated with a page when an error
+ * occurs that requires the cached contents of an inode to be written back or
+ * destroyed
+ * - Called if either PG_private or PG_private_2 is set on the page
+ * - Caller holds page lock
+ * - Return 0 if successful, -error otherwise
+ */
 static int nfs_launder_page(struct page *page)
 {
        struct inode *inode = page->mapping->host;
@@ -451,8 +472,14 @@ const struct address_space_operations nfs_file_aops = {
        .launder_page = nfs_launder_page,
 };
 
-static int nfs_vm_page_mkwrite(struct vm_area_struct *vma, struct page *page)
+/*
+ * Notification that a PTE pointing to an NFS page is about to be made
+ * writable, implying that someone is about to modify the page through a
+ * shared-writable mapping
+ */
+static int nfs_vm_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
+       struct page *page = vmf->page;
        struct file *filp = vma->vm_file;
        struct dentry *dentry = filp->f_path.dentry;
        unsigned pagelen;
@@ -483,6 +510,8 @@ static int nfs_vm_page_mkwrite(struct vm_area_struct *vma, struct page *page)
                ret = pagelen;
 out_unlock:
        unlock_page(page);
+       if (ret)
+               ret = VM_FAULT_SIGBUS;
        return ret;
 }