/*
 * Copyright (c) 2014 Christoph Hellwig.
 */
#include <linux/iomap.h>
#include "xfs.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_sb.h"
#include "xfs_mount.h"
#include "xfs_inode.h"
#include "xfs_trans.h"
#include "xfs_log.h"
#include "xfs_bmap.h"
#include "xfs_bmap_util.h"
#include "xfs_error.h"
#include "xfs_iomap.h"
#include "xfs_shared.h"
#include "xfs_bit.h"
#include "xfs_pnfs.h"

/*
 * Ensure that we do not have any outstanding pNFS layouts that can be used by
 * clients to directly read from or write to this inode.  This must be called
 * before every operation that can remove blocks from the extent map.
 * Additionally we call it during the write operation, where aren't concerned
 * about exposing unallocated blocks but just want to provide basic
 * synchronization between a local writer and pNFS clients.  mmap writes would
 * also benefit from this sort of synchronization, but due to the tricky locking
 * rules in the page fault path we don't bother.
 */
int
xfs_break_layouts(
        struct inode            *inode,
        uint                    *iolock)
{
        struct xfs_inode        *ip = XFS_I(inode);
        int                     error;

        ASSERT(xfs_isilocked(ip, XFS_IOLOCK_SHARED|XFS_IOLOCK_EXCL));

        while ((error = break_layout(inode, false) == -EWOULDBLOCK)) {
                xfs_iunlock(ip, *iolock);
                error = break_layout(inode, true);
                *iolock = XFS_IOLOCK_EXCL;
                xfs_ilock(ip, *iolock);
        }

        return error;
}

/*
 * Get a unique ID including its location so that the client can identify
 * the exported device.
 */
int
xfs_fs_get_uuid(
        struct super_block      *sb,
        u8                      *buf,
        u32                     *len,
        u64                     *offset)
{
        struct xfs_mount        *mp = XFS_M(sb);

        printk_once(KERN_NOTICE
"XFS (%s): using experimental pNFS feature, use at your own risk!\n",
                mp->m_fsname);

        if (*len < sizeof(uuid_t))
                return -EINVAL;

        memcpy(buf, &mp->m_sb.sb_uuid, sizeof(uuid_t));
        *len = sizeof(uuid_t);
        *offset = offsetof(struct xfs_dsb, sb_uuid);
        return 0;
}

/*
 * Get a layout for the pNFS client.
 */
int
xfs_fs_map_blocks(
        struct inode            *inode,
        loff_t                  offset,
        u64                     length,
        struct iomap            *iomap,
        bool                    write,
        u32                     *device_generation)
{
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_bmbt_irec    imap;
        xfs_fileoff_t           offset_fsb, end_fsb;
        loff_t                  limit;
        int                     bmapi_flags = XFS_BMAPI_ENTIRE;
        int                     nimaps = 1;
        uint                    lock_flags;
        int                     error = 0;

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        /*
         * We can't export inodes residing on the realtime device.  The realtime
         * device doesn't have a UUID to identify it, so the client has no way
         * to find it.
         */
        if (XFS_IS_REALTIME_INODE(ip))
                return -ENXIO;

        /*
         * The pNFS block layout spec actually supports reflink like
         * functionality, but the Linux pNFS server doesn't implement it yet.
         */
        if (xfs_is_reflink_inode(ip))
                return -ENXIO;

        /*
         * Lock out any other I/O before we flush and invalidate the pagecache,
         * and then hand out a layout to the remote system.  This is very
         * similar to direct I/O, except that the synchronization is much more
         * complicated.  See the comment near xfs_break_layouts for a detailed
         * explanation.
         */
        xfs_ilock(ip, XFS_IOLOCK_EXCL);

        error = -EINVAL;
        limit = mp->m_super->s_maxbytes;
        if (!write)
                limit = max(limit, round_up(i_size_read(inode),
                                     inode->i_sb->s_blocksize));
        if (offset > limit)
                goto out_unlock;
        if (offset > limit - length)
                length = limit - offset;

        error = filemap_write_and_wait(inode->i_mapping);
        if (error)
                goto out_unlock;
        error = invalidate_inode_pages2(inode->i_mapping);
        if (WARN_ON_ONCE(error))
                return error;

        end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + length);
        offset_fsb = XFS_B_TO_FSBT(mp, offset);

        lock_flags = xfs_ilock_data_map_shared(ip);
        error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb,
                                &imap, &nimaps, bmapi_flags);
        xfs_iunlock(ip, lock_flags);

        if (error)
                goto out_unlock;

        if (write) {
                enum xfs_prealloc_flags flags = 0;

                ASSERT(imap.br_startblock != DELAYSTARTBLOCK);

                if (!nimaps || imap.br_startblock == HOLESTARTBLOCK) {
                        /*
                         * xfs_iomap_write_direct() expects to take ownership of
                         * the shared ilock.
                         */
                        xfs_ilock(ip, XFS_ILOCK_SHARED);
                        error = xfs_iomap_write_direct(ip, offset, length,
                                                       &imap, nimaps);
                        if (error)
                                goto out_unlock;

                        /*
                         * Ensure the next transaction is committed
                         * synchronously so that the blocks allocated and
                         * handed out to the client are guaranteed to be
                         * present even after a server crash.
                         */
                        flags |= XFS_PREALLOC_SET | XFS_PREALLOC_SYNC;
                }

                error = xfs_update_prealloc_flags(ip, flags);
                if (error)
                        goto out_unlock;
        }
        xfs_iunlock(ip, XFS_IOLOCK_EXCL);

        xfs_bmbt_to_iomap(ip, iomap, &imap);
        *device_generation = mp->m_generation;
        return error;
out_unlock:
        xfs_iunlock(ip, XFS_IOLOCK_EXCL);
        return error;
}

/*
 * Ensure the size update falls into a valid allocated block.
 */
static int
xfs_pnfs_validate_isize(
        struct xfs_inode        *ip,
        xfs_off_t               isize)
{
        struct xfs_bmbt_irec    imap;
        int                     nimaps = 1;
        int                     error = 0;

        xfs_ilock(ip, XFS_ILOCK_SHARED);
        error = xfs_bmapi_read(ip, XFS_B_TO_FSBT(ip->i_mount, isize - 1), 1,
                                &imap, &nimaps, 0);
        xfs_iunlock(ip, XFS_ILOCK_SHARED);
        if (error)
                return error;

        if (imap.br_startblock == HOLESTARTBLOCK ||
            imap.br_startblock == DELAYSTARTBLOCK ||
            imap.br_state == XFS_EXT_UNWRITTEN)
                return -EIO;
        return 0;
}

/*
 * Make sure the blocks described by maps are stable on disk.  This includes
 * converting any unwritten extents, flushing the disk cache and updating the
 * time stamps.
 *
 * Note that we rely on the caller to always send us a timestamp update so that
 * we always commit a transaction here.  If that stops being true we will have
 * to manually flush the cache here similar to what the fsync code path does
 * for datasyncs on files that have no dirty metadata.
 */
int
xfs_fs_commit_blocks(
        struct inode            *inode,
        struct iomap            *maps,
        int                     nr_maps,
        struct iattr            *iattr)
{
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_trans        *tp;
        bool                    update_isize = false;
        int                     error, i;
        loff_t                  size;

        ASSERT(iattr->ia_valid & (ATTR_ATIME|ATTR_CTIME|ATTR_MTIME));

        xfs_ilock(ip, XFS_IOLOCK_EXCL);

        size = i_size_read(inode);
        if ((iattr->ia_valid & ATTR_SIZE) && iattr->ia_size > size) {
                update_isize = true;
                size = iattr->ia_size;
        }

        for (i = 0; i < nr_maps; i++) {
                u64 start, length, end;

                start = maps[i].offset;
                if (start > size)
                        continue;

                end = start + maps[i].length;
                if (end > size)
                        end = size;

                length = end - start;
                if (!length)
                        continue;
        
                /*
                 * Make sure reads through the pagecache see the new data.
                 */
                error = invalidate_inode_pages2_range(inode->i_mapping,
                                        start >> PAGE_SHIFT,
                                        (end - 1) >> PAGE_SHIFT);
                WARN_ON_ONCE(error);

                error = xfs_iomap_write_unwritten(ip, start, length);
                if (error)
                        goto out_drop_iolock;
        }

        if (update_isize) {
                error = xfs_pnfs_validate_isize(ip, size);
                if (error)
                        goto out_drop_iolock;
        }

        error = xfs_trans_alloc(mp, &M_RES(mp)->tr_ichange, 0, 0, 0, &tp);
        if (error)
                goto out_drop_iolock;

        xfs_ilock(ip, XFS_ILOCK_EXCL);
        xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);

        xfs_setattr_time(ip, iattr);
        if (update_isize) {
                i_size_write(inode, iattr->ia_size);
                ip->i_d.di_size = iattr->ia_size;
        }

        xfs_trans_set_sync(tp);
        error = xfs_trans_commit(tp);

out_drop_iolock:
        xfs_iunlock(ip, XFS_IOLOCK_EXCL);
        return error;
}