mm: fix exec activate_mm vs TLB shootdown and lazy tlb switching race

[linux/fpc-iii.git] / fs / gfs2 / file.c

/*
 * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
 * Copyright (C) 2004-2006 Red Hat, Inc.  All rights reserved.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU General Public License version 2.
 */

#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <linux/buffer_head.h>
#include <linux/pagemap.h>
#include <linux/uio.h>
#include <linux/blkdev.h>
#include <linux/mm.h>
#include <linux/mount.h>
#include <linux/fs.h>
#include <linux/gfs2_ondisk.h>
#include <linux/falloc.h>
#include <linux/swap.h>
#include <linux/crc32.h>
#include <linux/writeback.h>
#include <linux/uaccess.h>
#include <linux/dlm.h>
#include <linux/dlm_plock.h>
#include <linux/delay.h>

#include "gfs2.h"
#include "incore.h"
#include "bmap.h"
#include "dir.h"
#include "glock.h"
#include "glops.h"
#include "inode.h"
#include "log.h"
#include "meta_io.h"
#include "quota.h"
#include "rgrp.h"
#include "trans.h"
#include "util.h"

/**
 * gfs2_llseek - seek to a location in a file
 * @file: the file
 * @offset: the offset
 * @whence: Where to seek from (SEEK_SET, SEEK_CUR, or SEEK_END)
 *
 * SEEK_END requires the glock for the file because it references the
 * file's size.
 *
 * Returns: The new offset, or errno
 */

static loff_t gfs2_llseek(struct file *file, loff_t offset, int whence)
{
        struct gfs2_inode *ip = GFS2_I(file->f_mapping->host);
        struct gfs2_holder i_gh;
        loff_t error;

        switch (whence) {
        case SEEK_END: /* These reference inode->i_size */
        case SEEK_DATA:
        case SEEK_HOLE:
                error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY,
                                           &i_gh);
                if (!error) {
                        error = generic_file_llseek(file, offset, whence);
                        gfs2_glock_dq_uninit(&i_gh);
                }
                break;
        case SEEK_CUR:
        case SEEK_SET:
                error = generic_file_llseek(file, offset, whence);
                break;
        default:
                error = -EINVAL;
        }

        return error;
}

/**
 * gfs2_readdir - Iterator for a directory
 * @file: The directory to read from
 * @ctx: What to feed directory entries to
 *
 * Returns: errno
 */

static int gfs2_readdir(struct file *file, struct dir_context *ctx)
{
        struct inode *dir = file->f_mapping->host;
        struct gfs2_inode *dip = GFS2_I(dir);
        struct gfs2_holder d_gh;
        int error;

        error = gfs2_glock_nq_init(dip->i_gl, LM_ST_SHARED, 0, &d_gh);
        if (error)
                return error;

        error = gfs2_dir_read(dir, ctx, &file->f_ra);

        gfs2_glock_dq_uninit(&d_gh);

        return error;
}

/**
 * fsflags_cvt
 * @table: A table of 32 u32 flags
 * @val: a 32 bit value to convert
 *
 * This function can be used to convert between fsflags values and
 * GFS2's own flags values.
 *
 * Returns: the converted flags
 */
static u32 fsflags_cvt(const u32 *table, u32 val)
{
        u32 res = 0;
        while(val) {
                if (val & 1)
                        res |= *table;
                table++;
                val >>= 1;
        }
        return res;
}

static const u32 fsflags_to_gfs2[32] = {
        [3] = GFS2_DIF_SYNC,
        [4] = GFS2_DIF_IMMUTABLE,
        [5] = GFS2_DIF_APPENDONLY,
        [7] = GFS2_DIF_NOATIME,
        [12] = GFS2_DIF_EXHASH,
        [14] = GFS2_DIF_INHERIT_JDATA,
        [17] = GFS2_DIF_TOPDIR,
};

static const u32 gfs2_to_fsflags[32] = {
        [gfs2fl_Sync] = FS_SYNC_FL,
        [gfs2fl_Immutable] = FS_IMMUTABLE_FL,
        [gfs2fl_AppendOnly] = FS_APPEND_FL,
        [gfs2fl_NoAtime] = FS_NOATIME_FL,
        [gfs2fl_ExHash] = FS_INDEX_FL,
        [gfs2fl_TopLevel] = FS_TOPDIR_FL,
        [gfs2fl_InheritJdata] = FS_JOURNAL_DATA_FL,
};

static int gfs2_get_flags(struct file *filp, u32 __user *ptr)
{
        struct inode *inode = file_inode(filp);
        struct gfs2_inode *ip = GFS2_I(inode);
        struct gfs2_holder gh;
        int error;
        u32 fsflags;

        gfs2_holder_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
        error = gfs2_glock_nq(&gh);
        if (error)
                goto out_uninit;

        fsflags = fsflags_cvt(gfs2_to_fsflags, ip->i_diskflags);
        if (!S_ISDIR(inode->i_mode) && ip->i_diskflags & GFS2_DIF_JDATA)
                fsflags |= FS_JOURNAL_DATA_FL;
        if (put_user(fsflags, ptr))
                error = -EFAULT;

        gfs2_glock_dq(&gh);
out_uninit:
        gfs2_holder_uninit(&gh);
        return error;
}

void gfs2_set_inode_flags(struct inode *inode)
{
        struct gfs2_inode *ip = GFS2_I(inode);
        unsigned int flags = inode->i_flags;

        flags &= ~(S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC|S_NOSEC);
        if ((ip->i_eattr == 0) && !is_sxid(inode->i_mode))
                flags |= S_NOSEC;
        if (ip->i_diskflags & GFS2_DIF_IMMUTABLE)
                flags |= S_IMMUTABLE;
        if (ip->i_diskflags & GFS2_DIF_APPENDONLY)
                flags |= S_APPEND;
        if (ip->i_diskflags & GFS2_DIF_NOATIME)
                flags |= S_NOATIME;
        if (ip->i_diskflags & GFS2_DIF_SYNC)
                flags |= S_SYNC;
        inode->i_flags = flags;
}

/* Flags that can be set by user space */
#define GFS2_FLAGS_USER_SET (GFS2_DIF_JDATA|                    \
                             GFS2_DIF_IMMUTABLE|                \
                             GFS2_DIF_APPENDONLY|               \
                             GFS2_DIF_NOATIME|                  \
                             GFS2_DIF_SYNC|                     \
                             GFS2_DIF_SYSTEM|                   \
                             GFS2_DIF_TOPDIR|                   \
                             GFS2_DIF_INHERIT_JDATA)

/**
 * do_gfs2_set_flags - set flags on an inode
 * @filp: file pointer
 * @reqflags: The flags to set
 * @mask: Indicates which flags are valid
 *
 */
static int do_gfs2_set_flags(struct file *filp, u32 reqflags, u32 mask)
{
        struct inode *inode = file_inode(filp);
        struct gfs2_inode *ip = GFS2_I(inode);
        struct gfs2_sbd *sdp = GFS2_SB(inode);
        struct buffer_head *bh;
        struct gfs2_holder gh;
        int error;
        u32 new_flags, flags;

        error = mnt_want_write_file(filp);
        if (error)
                return error;

        error = gfs2_glock_nq_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &gh);
        if (error)
                goto out_drop_write;

        error = -EACCES;
        if (!inode_owner_or_capable(inode))
                goto out;

        error = 0;
        flags = ip->i_diskflags;
        new_flags = (flags & ~mask) | (reqflags & mask);
        if ((new_flags ^ flags) == 0)
                goto out;

        error = -EINVAL;
        if ((new_flags ^ flags) & ~GFS2_FLAGS_USER_SET)
                goto out;

        error = -EPERM;
        if (IS_IMMUTABLE(inode) && (new_flags & GFS2_DIF_IMMUTABLE))
                goto out;
        if (IS_APPEND(inode) && (new_flags & GFS2_DIF_APPENDONLY))
                goto out;
        if (((new_flags ^ flags) & GFS2_DIF_IMMUTABLE) &&
            !capable(CAP_LINUX_IMMUTABLE))
                goto out;
        if (!IS_IMMUTABLE(inode)) {
                error = gfs2_permission(inode, MAY_WRITE);
                if (error)
                        goto out;
        }
        if ((flags ^ new_flags) & GFS2_DIF_JDATA) {
                if (new_flags & GFS2_DIF_JDATA)
                        gfs2_log_flush(sdp, ip->i_gl, NORMAL_FLUSH);
                error = filemap_fdatawrite(inode->i_mapping);
                if (error)
                        goto out;
                error = filemap_fdatawait(inode->i_mapping);
                if (error)
                        goto out;
                if (new_flags & GFS2_DIF_JDATA)
                        gfs2_ordered_del_inode(ip);
        }
        error = gfs2_trans_begin(sdp, RES_DINODE, 0);
        if (error)
                goto out;
        error = gfs2_meta_inode_buffer(ip, &bh);
        if (error)
                goto out_trans_end;
        gfs2_trans_add_meta(ip->i_gl, bh);
        ip->i_diskflags = new_flags;
        gfs2_dinode_out(ip, bh->b_data);
        brelse(bh);
        gfs2_set_inode_flags(inode);
        gfs2_set_aops(inode);
out_trans_end:
        gfs2_trans_end(sdp);
out:
        gfs2_glock_dq_uninit(&gh);
out_drop_write:
        mnt_drop_write_file(filp);
        return error;
}

static int gfs2_set_flags(struct file *filp, u32 __user *ptr)
{
        struct inode *inode = file_inode(filp);
        u32 fsflags, gfsflags;

        if (get_user(fsflags, ptr))
                return -EFAULT;

        gfsflags = fsflags_cvt(fsflags_to_gfs2, fsflags);
        if (!S_ISDIR(inode->i_mode)) {
                gfsflags &= ~GFS2_DIF_TOPDIR;
                if (gfsflags & GFS2_DIF_INHERIT_JDATA)
                        gfsflags ^= (GFS2_DIF_JDATA | GFS2_DIF_INHERIT_JDATA);
                return do_gfs2_set_flags(filp, gfsflags, ~GFS2_DIF_SYSTEM);
        }
        return do_gfs2_set_flags(filp, gfsflags, ~(GFS2_DIF_SYSTEM | GFS2_DIF_JDATA));
}

static long gfs2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
        switch(cmd) {
        case FS_IOC_GETFLAGS:
                return gfs2_get_flags(filp, (u32 __user *)arg);
        case FS_IOC_SETFLAGS:
                return gfs2_set_flags(filp, (u32 __user *)arg);
        case FITRIM:
                return gfs2_fitrim(filp, (void __user *)arg);
        }
        return -ENOTTY;
}

/**
 * gfs2_size_hint - Give a hint to the size of a write request
 * @filep: The struct file
 * @offset: The file offset of the write
 * @size: The length of the write
 *
 * When we are about to do a write, this function records the total
 * write size in order to provide a suitable hint to the lower layers
 * about how many blocks will be required.
 *
 */

static void gfs2_size_hint(struct file *filep, loff_t offset, size_t size)
{
        struct inode *inode = file_inode(filep);
        struct gfs2_sbd *sdp = GFS2_SB(inode);
        struct gfs2_inode *ip = GFS2_I(inode);
        size_t blks = (size + sdp->sd_sb.sb_bsize - 1) >> sdp->sd_sb.sb_bsize_shift;
        int hint = min_t(size_t, INT_MAX, blks);

        if (hint > atomic_read(&ip->i_res.rs_sizehint))
                atomic_set(&ip->i_res.rs_sizehint, hint);
}

/**
 * gfs2_allocate_page_backing - Use bmap to allocate blocks
 * @page: The (locked) page to allocate backing for
 *
 * We try to allocate all the blocks required for the page in
 * one go. This might fail for various reasons, so we keep
 * trying until all the blocks to back this page are allocated.
 * If some of the blocks are already allocated, thats ok too.
 */

static int gfs2_allocate_page_backing(struct page *page)
{
        struct inode *inode = page->mapping->host;
        struct buffer_head bh;
        unsigned long size = PAGE_SIZE;
        u64 lblock = page->index << (PAGE_SHIFT - inode->i_blkbits);

        do {
                bh.b_state = 0;
                bh.b_size = size;
                gfs2_block_map(inode, lblock, &bh, 1);
                if (!buffer_mapped(&bh))
                        return -EIO;
                size -= bh.b_size;
                lblock += (bh.b_size >> inode->i_blkbits);
        } while(size > 0);
        return 0;
}

/**
 * gfs2_page_mkwrite - Make a shared, mmap()ed, page writable
 * @vma: The virtual memory area
 * @vmf: The virtual memory fault containing the page to become writable
 *
 * When the page becomes writable, we need to ensure that we have
 * blocks allocated on disk to back that page.
 */

static int gfs2_page_mkwrite(struct vm_fault *vmf)
{
        struct page *page = vmf->page;
        struct inode *inode = file_inode(vmf->vma->vm_file);
        struct gfs2_inode *ip = GFS2_I(inode);
        struct gfs2_sbd *sdp = GFS2_SB(inode);
        struct gfs2_alloc_parms ap = { .aflags = 0, };
        unsigned long last_index;
        u64 pos = page->index << PAGE_SHIFT;
        unsigned int data_blocks, ind_blocks, rblocks;
        struct gfs2_holder gh;
        loff_t size;
        int ret;

        sb_start_pagefault(inode->i_sb);

        ret = gfs2_rsqa_alloc(ip);
        if (ret)
                goto out;

        gfs2_size_hint(vmf->vma->vm_file, pos, PAGE_SIZE);

        gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &gh);
        ret = gfs2_glock_nq(&gh);
        if (ret)
                goto out_uninit;

        /* Update file times before taking page lock */
        file_update_time(vmf->vma->vm_file);

        set_bit(GLF_DIRTY, &ip->i_gl->gl_flags);
        set_bit(GIF_SW_PAGED, &ip->i_flags);

        if (!gfs2_write_alloc_required(ip, pos, PAGE_SIZE)) {
                lock_page(page);
                if (!PageUptodate(page) || page->mapping != inode->i_mapping) {
                        ret = -EAGAIN;
                        unlock_page(page);
                }
                goto out_unlock;
        }

        ret = gfs2_rindex_update(sdp);
        if (ret)
                goto out_unlock;

        gfs2_write_calc_reserv(ip, PAGE_SIZE, &data_blocks, &ind_blocks);
        ap.target = data_blocks + ind_blocks;
        ret = gfs2_quota_lock_check(ip, &ap);
        if (ret)
                goto out_unlock;
        ret = gfs2_inplace_reserve(ip, &ap);
        if (ret)
                goto out_quota_unlock;

        rblocks = RES_DINODE + ind_blocks;
        if (gfs2_is_jdata(ip))
                rblocks += data_blocks ? data_blocks : 1;
        if (ind_blocks || data_blocks) {
                rblocks += RES_STATFS + RES_QUOTA;
                rblocks += gfs2_rg_blocks(ip, data_blocks + ind_blocks);
        }
        ret = gfs2_trans_begin(sdp, rblocks, 0);
        if (ret)
                goto out_trans_fail;

        lock_page(page);
        ret = -EINVAL;
        size = i_size_read(inode);
        last_index = (size - 1) >> PAGE_SHIFT;
        /* Check page index against inode size */
        if (size == 0 || (page->index > last_index))
                goto out_trans_end;

        ret = -EAGAIN;
        /* If truncated, we must retry the operation, we may have raced
         * with the glock demotion code.
         */
        if (!PageUptodate(page) || page->mapping != inode->i_mapping)
                goto out_trans_end;

        /* Unstuff, if required, and allocate backing blocks for page */
        ret = 0;
        if (gfs2_is_stuffed(ip))
                ret = gfs2_unstuff_dinode(ip, page);
        if (ret == 0)
                ret = gfs2_allocate_page_backing(page);

out_trans_end:
        if (ret)
                unlock_page(page);
        gfs2_trans_end(sdp);
out_trans_fail:
        gfs2_inplace_release(ip);
out_quota_unlock:
        gfs2_quota_unlock(ip);
out_unlock:
        gfs2_glock_dq(&gh);
out_uninit:
        gfs2_holder_uninit(&gh);
        if (ret == 0) {
                set_page_dirty(page);
                wait_for_stable_page(page);
        }
out:
        sb_end_pagefault(inode->i_sb);
        return block_page_mkwrite_return(ret);
}

static const struct vm_operations_struct gfs2_vm_ops = {
        .fault = filemap_fault,
        .map_pages = filemap_map_pages,
        .page_mkwrite = gfs2_page_mkwrite,
};

/**
 * gfs2_mmap -
 * @file: The file to map
 * @vma: The VMA which described the mapping
 *
 * There is no need to get a lock here unless we should be updating
 * atime. We ignore any locking errors since the only consequence is
 * a missed atime update (which will just be deferred until later).
 *
 * Returns: 0
 */

static int gfs2_mmap(struct file *file, struct vm_area_struct *vma)
{
        struct gfs2_inode *ip = GFS2_I(file->f_mapping->host);

        if (!(file->f_flags & O_NOATIME) &&
            !IS_NOATIME(&ip->i_inode)) {
                struct gfs2_holder i_gh;
                int error;

                error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY,
                                           &i_gh);
                if (error)
                        return error;
                /* grab lock to update inode */
                gfs2_glock_dq_uninit(&i_gh);
                file_accessed(file);
        }
        vma->vm_ops = &gfs2_vm_ops;

        return 0;
}

/**
 * gfs2_open_common - This is common to open and atomic_open
 * @inode: The inode being opened
 * @file: The file being opened
 *
 * This maybe called under a glock or not depending upon how it has
 * been called. We must always be called under a glock for regular
 * files, however. For other file types, it does not matter whether
 * we hold the glock or not.
 *
 * Returns: Error code or 0 for success
 */

int gfs2_open_common(struct inode *inode, struct file *file)
{
        struct gfs2_file *fp;
        int ret;

        if (S_ISREG(inode->i_mode)) {
                ret = generic_file_open(inode, file);
                if (ret)
                        return ret;
        }

        fp = kzalloc(sizeof(struct gfs2_file), GFP_NOFS);
        if (!fp)
                return -ENOMEM;

        mutex_init(&fp->f_fl_mutex);

        gfs2_assert_warn(GFS2_SB(inode), !file->private_data);
        file->private_data = fp;
        return 0;
}

/**
 * gfs2_open - open a file
 * @inode: the inode to open
 * @file: the struct file for this opening
 *
 * After atomic_open, this function is only used for opening files
 * which are already cached. We must still get the glock for regular
 * files to ensure that we have the file size uptodate for the large
 * file check which is in the common code. That is only an issue for
 * regular files though.
 *
 * Returns: errno
 */

static int gfs2_open(struct inode *inode, struct file *file)
{
        struct gfs2_inode *ip = GFS2_I(inode);
        struct gfs2_holder i_gh;
        int error;
        bool need_unlock = false;

        if (S_ISREG(ip->i_inode.i_mode)) {
                error = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, LM_FLAG_ANY,
                                           &i_gh);
                if (error)
                        return error;
                need_unlock = true;
        }

        error = gfs2_open_common(inode, file);

        if (need_unlock)
                gfs2_glock_dq_uninit(&i_gh);

        return error;
}

/**
 * gfs2_release - called to close a struct file
 * @inode: the inode the struct file belongs to
 * @file: the struct file being closed
 *
 * Returns: errno
 */

static int gfs2_release(struct inode *inode, struct file *file)
{
        struct gfs2_inode *ip = GFS2_I(inode);

        kfree(file->private_data);
        file->private_data = NULL;

        if (!(file->f_mode & FMODE_WRITE))
                return 0;

        gfs2_rsqa_delete(ip, &inode->i_writecount);
        return 0;
}

/**
 * gfs2_fsync - sync the dirty data for a file (across the cluster)
 * @file: the file that points to the dentry
 * @start: the start position in the file to sync
 * @end: the end position in the file to sync
 * @datasync: set if we can ignore timestamp changes
 *
 * We split the data flushing here so that we don't wait for the data
 * until after we've also sent the metadata to disk. Note that for
 * data=ordered, we will write & wait for the data at the log flush
 * stage anyway, so this is unlikely to make much of a difference
 * except in the data=writeback case.
 *
 * If the fdatawrite fails due to any reason except -EIO, we will
 * continue the remainder of the fsync, although we'll still report
 * the error at the end. This is to match filemap_write_and_wait_range()
 * behaviour.
 *
 * Returns: errno
 */

static int gfs2_fsync(struct file *file, loff_t start, loff_t end,
                      int datasync)
{
        struct address_space *mapping = file->f_mapping;
        struct inode *inode = mapping->host;
        int sync_state = inode->i_state & I_DIRTY_ALL;
        struct gfs2_inode *ip = GFS2_I(inode);
        int ret = 0, ret1 = 0;

        if (mapping->nrpages) {
                ret1 = filemap_fdatawrite_range(mapping, start, end);
                if (ret1 == -EIO)
                        return ret1;
        }

        if (!gfs2_is_jdata(ip))
                sync_state &= ~I_DIRTY_PAGES;
        if (datasync)
                sync_state &= ~(I_DIRTY_SYNC | I_DIRTY_TIME);

        if (sync_state) {
                ret = sync_inode_metadata(inode, 1);
                if (ret)
                        return ret;
                if (gfs2_is_jdata(ip))
                        ret = file_write_and_wait(file);
                if (ret)
                        return ret;
                gfs2_ail_flush(ip->i_gl, 1);
        }

        if (mapping->nrpages)
                ret = file_fdatawait_range(file, start, end);

        return ret ? ret : ret1;
}

/**
 * gfs2_file_write_iter - Perform a write to a file
 * @iocb: The io context
 * @iov: The data to write
 * @nr_segs: Number of @iov segments
 * @pos: The file position
 *
 * We have to do a lock/unlock here to refresh the inode size for
 * O_APPEND writes, otherwise we can land up writing at the wrong
 * offset. There is still a race, but provided the app is using its
 * own file locking, this will make O_APPEND work as expected.
 *
 */

static ssize_t gfs2_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
{
        struct file *file = iocb->ki_filp;
        struct gfs2_inode *ip = GFS2_I(file_inode(file));
        int ret;

        ret = gfs2_rsqa_alloc(ip);
        if (ret)
                return ret;

        gfs2_size_hint(file, iocb->ki_pos, iov_iter_count(from));

        if (iocb->ki_flags & IOCB_APPEND) {
                struct gfs2_holder gh;

                ret = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
                if (ret)
                        return ret;
                gfs2_glock_dq_uninit(&gh);
        }

        return generic_file_write_iter(iocb, from);
}

static int fallocate_chunk(struct inode *inode, loff_t offset, loff_t len,
                           int mode)
{
        struct gfs2_inode *ip = GFS2_I(inode);
        struct buffer_head *dibh;
        int error;
        unsigned int nr_blks;
        sector_t lblock = offset >> inode->i_blkbits;

        error = gfs2_meta_inode_buffer(ip, &dibh);
        if (unlikely(error))
                return error;

        gfs2_trans_add_meta(ip->i_gl, dibh);

        if (gfs2_is_stuffed(ip)) {
                error = gfs2_unstuff_dinode(ip, NULL);
                if (unlikely(error))
                        goto out;
        }

        while (len) {
                struct buffer_head bh_map = { .b_state = 0, .b_blocknr = 0 };
                bh_map.b_size = len;
                set_buffer_zeronew(&bh_map);

                error = gfs2_block_map(inode, lblock, &bh_map, 1);
                if (unlikely(error))
                        goto out;
                len -= bh_map.b_size;
                nr_blks = bh_map.b_size >> inode->i_blkbits;
                lblock += nr_blks;
                if (!buffer_new(&bh_map))
                        continue;
                if (unlikely(!buffer_zeronew(&bh_map))) {
                        error = -EIO;
                        goto out;
                }
        }
out:
        brelse(dibh);
        return error;
}
/**
 * calc_max_reserv() - Reverse of write_calc_reserv. Given a number of
 *                     blocks, determine how many bytes can be written.
 * @ip:          The inode in question.
 * @len:         Max cap of bytes. What we return in *len must be <= this.
 * @data_blocks: Compute and return the number of data blocks needed
 * @ind_blocks:  Compute and return the number of indirect blocks needed
 * @max_blocks:  The total blocks available to work with.
 *
 * Returns: void, but @len, @data_blocks and @ind_blocks are filled in.
 */
static void calc_max_reserv(struct gfs2_inode *ip, loff_t *len,
                            unsigned int *data_blocks, unsigned int *ind_blocks,
                            unsigned int max_blocks)
{
        loff_t max = *len;
        const struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
        unsigned int tmp, max_data = max_blocks - 3 * (sdp->sd_max_height - 1);

        for (tmp = max_data; tmp > sdp->sd_diptrs;) {
                tmp = DIV_ROUND_UP(tmp, sdp->sd_inptrs);
                max_data -= tmp;
        }

        *data_blocks = max_data;
        *ind_blocks = max_blocks - max_data;
        *len = ((loff_t)max_data - 3) << sdp->sd_sb.sb_bsize_shift;
        if (*len > max) {
                *len = max;
                gfs2_write_calc_reserv(ip, max, data_blocks, ind_blocks);
        }
}

static long __gfs2_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
{
        struct inode *inode = file_inode(file);
        struct gfs2_sbd *sdp = GFS2_SB(inode);
        struct gfs2_inode *ip = GFS2_I(inode);
        struct gfs2_alloc_parms ap = { .aflags = 0, };
        unsigned int data_blocks = 0, ind_blocks = 0, rblocks;
        loff_t bytes, max_bytes, max_blks;
        int error;
        const loff_t pos = offset;
        const loff_t count = len;
        loff_t bsize_mask = ~((loff_t)sdp->sd_sb.sb_bsize - 1);
        loff_t next = (offset + len - 1) >> sdp->sd_sb.sb_bsize_shift;
        loff_t max_chunk_size = UINT_MAX & bsize_mask;

        next = (next + 1) << sdp->sd_sb.sb_bsize_shift;

        offset &= bsize_mask;

        len = next - offset;
        bytes = sdp->sd_max_rg_data * sdp->sd_sb.sb_bsize / 2;
        if (!bytes)
                bytes = UINT_MAX;
        bytes &= bsize_mask;
        if (bytes == 0)
                bytes = sdp->sd_sb.sb_bsize;

        gfs2_size_hint(file, offset, len);

        gfs2_write_calc_reserv(ip, PAGE_SIZE, &data_blocks, &ind_blocks);
        ap.min_target = data_blocks + ind_blocks;

        while (len > 0) {
                if (len < bytes)
                        bytes = len;
                if (!gfs2_write_alloc_required(ip, offset, bytes)) {
                        len -= bytes;
                        offset += bytes;
                        continue;
                }

                /* We need to determine how many bytes we can actually
                 * fallocate without exceeding quota or going over the
                 * end of the fs. We start off optimistically by assuming
                 * we can write max_bytes */
                max_bytes = (len > max_chunk_size) ? max_chunk_size : len;

                /* Since max_bytes is most likely a theoretical max, we
                 * calculate a more realistic 'bytes' to serve as a good
                 * starting point for the number of bytes we may be able
                 * to write */
                gfs2_write_calc_reserv(ip, bytes, &data_blocks, &ind_blocks);
                ap.target = data_blocks + ind_blocks;

                error = gfs2_quota_lock_check(ip, &ap);
                if (error)
                        return error;
                /* ap.allowed tells us how many blocks quota will allow
                 * us to write. Check if this reduces max_blks */
                max_blks = UINT_MAX;
                if (ap.allowed)
                        max_blks = ap.allowed;

                error = gfs2_inplace_reserve(ip, &ap);
                if (error)
                        goto out_qunlock;

                /* check if the selected rgrp limits our max_blks further */
                if (ap.allowed && ap.allowed < max_blks)
                        max_blks = ap.allowed;

                /* Almost done. Calculate bytes that can be written using
                 * max_blks. We also recompute max_bytes, data_blocks and
                 * ind_blocks */
                calc_max_reserv(ip, &max_bytes, &data_blocks,
                                &ind_blocks, max_blks);

                rblocks = RES_DINODE + ind_blocks + RES_STATFS + RES_QUOTA +
                          RES_RG_HDR + gfs2_rg_blocks(ip, data_blocks + ind_blocks);
                if (gfs2_is_jdata(ip))
                        rblocks += data_blocks ? data_blocks : 1;

                error = gfs2_trans_begin(sdp, rblocks,
                                         PAGE_SIZE/sdp->sd_sb.sb_bsize);
                if (error)
                        goto out_trans_fail;

                error = fallocate_chunk(inode, offset, max_bytes, mode);
                gfs2_trans_end(sdp);

                if (error)
                        goto out_trans_fail;

                len -= max_bytes;
                offset += max_bytes;
                gfs2_inplace_release(ip);
                gfs2_quota_unlock(ip);
        }

        if (!(mode & FALLOC_FL_KEEP_SIZE) && (pos + count) > inode->i_size) {
                i_size_write(inode, pos + count);
                file_update_time(file);
                mark_inode_dirty(inode);
        }

        if ((file->f_flags & O_DSYNC) || IS_SYNC(file->f_mapping->host))
                return vfs_fsync_range(file, pos, pos + count - 1,
                               (file->f_flags & __O_SYNC) ? 0 : 1);
        return 0;

out_trans_fail:
        gfs2_inplace_release(ip);
out_qunlock:
        gfs2_quota_unlock(ip);
        return error;
}

static long gfs2_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
{
        struct inode *inode = file_inode(file);
        struct gfs2_sbd *sdp = GFS2_SB(inode);
        struct gfs2_inode *ip = GFS2_I(inode);
        struct gfs2_holder gh;
        int ret;

        if (mode & ~FALLOC_FL_KEEP_SIZE)
                return -EOPNOTSUPP;
        /* fallocate is needed by gfs2_grow to reserve space in the rindex */
        if (gfs2_is_jdata(ip) && inode != sdp->sd_rindex)
                return -EOPNOTSUPP;

        inode_lock(inode);

        gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &gh);
        ret = gfs2_glock_nq(&gh);
        if (ret)
                goto out_uninit;

        if (!(mode & FALLOC_FL_KEEP_SIZE) &&
            (offset + len) > inode->i_size) {
                ret = inode_newsize_ok(inode, offset + len);
                if (ret)
                        goto out_unlock;
        }

        ret = get_write_access(inode);
        if (ret)
                goto out_unlock;

        ret = gfs2_rsqa_alloc(ip);
        if (ret)
                goto out_putw;

        ret = __gfs2_fallocate(file, mode, offset, len);
        if (ret)
                gfs2_rs_deltree(&ip->i_res);

out_putw:
        put_write_access(inode);
out_unlock:
        gfs2_glock_dq(&gh);
out_uninit:
        gfs2_holder_uninit(&gh);
        inode_unlock(inode);
        return ret;
}

static ssize_t gfs2_file_splice_write(struct pipe_inode_info *pipe,
                                      struct file *out, loff_t *ppos,
                                      size_t len, unsigned int flags)
{
        int error;
        struct gfs2_inode *ip = GFS2_I(out->f_mapping->host);

        error = gfs2_rsqa_alloc(ip);
        if (error)
                return (ssize_t)error;

        gfs2_size_hint(out, *ppos, len);

        return iter_file_splice_write(pipe, out, ppos, len, flags);
}

#ifdef CONFIG_GFS2_FS_LOCKING_DLM

/**
 * gfs2_lock - acquire/release a posix lock on a file
 * @file: the file pointer
 * @cmd: either modify or retrieve lock state, possibly wait
 * @fl: type and range of lock
 *
 * Returns: errno
 */

static int gfs2_lock(struct file *file, int cmd, struct file_lock *fl)
{
        struct gfs2_inode *ip = GFS2_I(file->f_mapping->host);
        struct gfs2_sbd *sdp = GFS2_SB(file->f_mapping->host);
        struct lm_lockstruct *ls = &sdp->sd_lockstruct;

        if (!(fl->fl_flags & FL_POSIX))
                return -ENOLCK;
        if (__mandatory_lock(&ip->i_inode) && fl->fl_type != F_UNLCK)
                return -ENOLCK;

        if (cmd == F_CANCELLK) {
                /* Hack: */
                cmd = F_SETLK;
                fl->fl_type = F_UNLCK;
        }
        if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags))) {
                if (fl->fl_type == F_UNLCK)
                        locks_lock_file_wait(file, fl);
                return -EIO;
        }
        if (IS_GETLK(cmd))
                return dlm_posix_get(ls->ls_dlm, ip->i_no_addr, file, fl);
        else if (fl->fl_type == F_UNLCK)
                return dlm_posix_unlock(ls->ls_dlm, ip->i_no_addr, file, fl);
        else
                return dlm_posix_lock(ls->ls_dlm, ip->i_no_addr, file, cmd, fl);
}

static int do_flock(struct file *file, int cmd, struct file_lock *fl)
{
        struct gfs2_file *fp = file->private_data;
        struct gfs2_holder *fl_gh = &fp->f_fl_gh;
        struct gfs2_inode *ip = GFS2_I(file_inode(file));
        struct gfs2_glock *gl;
        unsigned int state;
        u16 flags;
        int error = 0;
        int sleeptime;

        state = (fl->fl_type == F_WRLCK) ? LM_ST_EXCLUSIVE : LM_ST_SHARED;
        flags = (IS_SETLKW(cmd) ? 0 : LM_FLAG_TRY_1CB) | GL_EXACT;

        mutex_lock(&fp->f_fl_mutex);

        if (gfs2_holder_initialized(fl_gh)) {
                if (fl_gh->gh_state == state)
                        goto out;
                locks_lock_file_wait(file,
                                     &(struct file_lock) {
                                             .fl_type = F_UNLCK,
                                             .fl_flags = FL_FLOCK
                                     });
                gfs2_glock_dq(fl_gh);
                gfs2_holder_reinit(state, flags, fl_gh);
        } else {
                error = gfs2_glock_get(GFS2_SB(&ip->i_inode), ip->i_no_addr,
                                       &gfs2_flock_glops, CREATE, &gl);
                if (error)
                        goto out;
                gfs2_holder_init(gl, state, flags, fl_gh);
                gfs2_glock_put(gl);
        }
        for (sleeptime = 1; sleeptime <= 4; sleeptime <<= 1) {
                error = gfs2_glock_nq(fl_gh);
                if (error != GLR_TRYFAILED)
                        break;
                fl_gh->gh_flags = LM_FLAG_TRY | GL_EXACT;
                fl_gh->gh_error = 0;
                msleep(sleeptime);
        }
        if (error) {
                gfs2_holder_uninit(fl_gh);
                if (error == GLR_TRYFAILED)
                        error = -EAGAIN;
        } else {
                error = locks_lock_file_wait(file, fl);
                gfs2_assert_warn(GFS2_SB(&ip->i_inode), !error);
        }

out:
        mutex_unlock(&fp->f_fl_mutex);
        return error;
}

static void do_unflock(struct file *file, struct file_lock *fl)
{
        struct gfs2_file *fp = file->private_data;
        struct gfs2_holder *fl_gh = &fp->f_fl_gh;

        mutex_lock(&fp->f_fl_mutex);
        locks_lock_file_wait(file, fl);
        if (gfs2_holder_initialized(fl_gh)) {
                gfs2_glock_dq(fl_gh);
                gfs2_holder_uninit(fl_gh);
        }
        mutex_unlock(&fp->f_fl_mutex);
}

/**
 * gfs2_flock - acquire/release a flock lock on a file
 * @file: the file pointer
 * @cmd: either modify or retrieve lock state, possibly wait
 * @fl: type and range of lock
 *
 * Returns: errno
 */

static int gfs2_flock(struct file *file, int cmd, struct file_lock *fl)
{
        if (!(fl->fl_flags & FL_FLOCK))
                return -ENOLCK;
        if (fl->fl_type & LOCK_MAND)
                return -EOPNOTSUPP;

        if (fl->fl_type == F_UNLCK) {
                do_unflock(file, fl);
                return 0;
        } else {
                return do_flock(file, cmd, fl);
        }
}

const struct file_operations gfs2_file_fops = {
        .llseek         = gfs2_llseek,
        .read_iter      = generic_file_read_iter,
        .write_iter     = gfs2_file_write_iter,
        .unlocked_ioctl = gfs2_ioctl,
        .mmap           = gfs2_mmap,
        .open           = gfs2_open,
        .release        = gfs2_release,
        .fsync          = gfs2_fsync,
        .lock           = gfs2_lock,
        .flock          = gfs2_flock,
        .splice_read    = generic_file_splice_read,
        .splice_write   = gfs2_file_splice_write,
        .setlease       = simple_nosetlease,
        .fallocate      = gfs2_fallocate,
};

const struct file_operations gfs2_dir_fops = {
        .iterate_shared = gfs2_readdir,
        .unlocked_ioctl = gfs2_ioctl,
        .open           = gfs2_open,
        .release        = gfs2_release,
        .fsync          = gfs2_fsync,
        .lock           = gfs2_lock,
        .flock          = gfs2_flock,
        .llseek         = default_llseek,
};

#endif /* CONFIG_GFS2_FS_LOCKING_DLM */

const struct file_operations gfs2_file_fops_nolock = {
        .llseek         = gfs2_llseek,
        .read_iter      = generic_file_read_iter,
        .write_iter     = gfs2_file_write_iter,
        .unlocked_ioctl = gfs2_ioctl,
        .mmap           = gfs2_mmap,
        .open           = gfs2_open,
        .release        = gfs2_release,
        .fsync          = gfs2_fsync,
        .splice_read    = generic_file_splice_read,
        .splice_write   = gfs2_file_splice_write,
        .setlease       = generic_setlease,
        .fallocate      = gfs2_fallocate,
};

const struct file_operations gfs2_dir_fops_nolock = {
        .iterate_shared = gfs2_readdir,
        .unlocked_ioctl = gfs2_ioctl,
        .open           = gfs2_open,
        .release        = gfs2_release,
        .fsync          = gfs2_fsync,
        .llseek         = default_llseek,
};