// SPDX-License-Identifier: GPL-2.0-only
/*
* This file is part of UBIFS.
*
* Copyright (C) 2006-2008 Nokia Corporation.
*
* Authors: Artem Bityutskiy (Битюцкий Артём)
* Adrian Hunter
*/
/*
* This file implements VFS file and inode operations for regular files, device
* nodes and symlinks as well as address space operations.
*
* UBIFS uses 2 page flags: @PG_private and @PG_checked. @PG_private is set if
* the page is dirty and is used for optimization purposes - dirty pages are
* not budgeted so the flag shows that 'ubifs_write_end()' should not release
* the budget for this page. The @PG_checked flag is set if full budgeting is
* required for the page e.g., when it corresponds to a file hole or it is
* beyond the file size. The budgeting is done in 'ubifs_write_begin()', because
* it is OK to fail in this function, and the budget is released in
* 'ubifs_write_end()'. So the @PG_private and @PG_checked flags carry
* information about how the page was budgeted, to make it possible to release
* the budget properly.
*
* A thing to keep in mind: inode @i_mutex is locked in most VFS operations we
* implement. However, this is not true for 'ubifs_writepage()', which may be
* called with @i_mutex unlocked. For example, when flusher thread is doing
* background write-back, it calls 'ubifs_writepage()' with unlocked @i_mutex.
* At "normal" work-paths the @i_mutex is locked in 'ubifs_writepage()', e.g.
* in the "sys_write -> alloc_pages -> direct reclaim path". So, in
* 'ubifs_writepage()' we are only guaranteed that the page is locked.
*
* Similarly, @i_mutex is not always locked in 'ubifs_readpage()', e.g., the
* read-ahead path does not lock it ("sys_read -> generic_file_aio_read ->
* ondemand_readahead -> readpage"). In case of readahead, @I_SYNC flag is not
* set as well. However, UBIFS disables readahead.
*/
#inclu
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