gpio: rcar: Fix runtime PM imbalance on error

[linux/fpc-iii.git] / fs / xfs / xfs_iomap.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2000-2006 Silicon Graphics, Inc.
 * Copyright (c) 2016-2018 Christoph Hellwig.
 * All Rights Reserved.
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_inode.h"
#include "xfs_btree.h"
#include "xfs_bmap_btree.h"
#include "xfs_bmap.h"
#include "xfs_bmap_util.h"
#include "xfs_errortag.h"
#include "xfs_error.h"
#include "xfs_trans.h"
#include "xfs_trans_space.h"
#include "xfs_inode_item.h"
#include "xfs_iomap.h"
#include "xfs_trace.h"
#include "xfs_quota.h"
#include "xfs_dquot_item.h"
#include "xfs_dquot.h"
#include "xfs_reflink.h"


#define XFS_ALLOC_ALIGN(mp, off) \
        (((off) >> mp->m_allocsize_log) << mp->m_allocsize_log)

static int
xfs_alert_fsblock_zero(
        xfs_inode_t     *ip,
        xfs_bmbt_irec_t *imap)
{
        xfs_alert_tag(ip->i_mount, XFS_PTAG_FSBLOCK_ZERO,
                        "Access to block zero in inode %llu "
                        "start_block: %llx start_off: %llx "
                        "blkcnt: %llx extent-state: %x",
                (unsigned long long)ip->i_ino,
                (unsigned long long)imap->br_startblock,
                (unsigned long long)imap->br_startoff,
                (unsigned long long)imap->br_blockcount,
                imap->br_state);
        return -EFSCORRUPTED;
}

int
xfs_bmbt_to_iomap(
        struct xfs_inode        *ip,
        struct iomap            *iomap,
        struct xfs_bmbt_irec    *imap,
        u16                     flags)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_buftarg      *target = xfs_inode_buftarg(ip);

        if (unlikely(!xfs_valid_startblock(ip, imap->br_startblock)))
                return xfs_alert_fsblock_zero(ip, imap);

        if (imap->br_startblock == HOLESTARTBLOCK) {
                iomap->addr = IOMAP_NULL_ADDR;
                iomap->type = IOMAP_HOLE;
        } else if (imap->br_startblock == DELAYSTARTBLOCK ||
                   isnullstartblock(imap->br_startblock)) {
                iomap->addr = IOMAP_NULL_ADDR;
                iomap->type = IOMAP_DELALLOC;
        } else {
                iomap->addr = BBTOB(xfs_fsb_to_db(ip, imap->br_startblock));
                if (imap->br_state == XFS_EXT_UNWRITTEN)
                        iomap->type = IOMAP_UNWRITTEN;
                else
                        iomap->type = IOMAP_MAPPED;
        }
        iomap->offset = XFS_FSB_TO_B(mp, imap->br_startoff);
        iomap->length = XFS_FSB_TO_B(mp, imap->br_blockcount);
        iomap->bdev = target->bt_bdev;
        iomap->dax_dev = target->bt_daxdev;
        iomap->flags = flags;

        if (xfs_ipincount(ip) &&
            (ip->i_itemp->ili_fsync_fields & ~XFS_ILOG_TIMESTAMP))
                iomap->flags |= IOMAP_F_DIRTY;
        return 0;
}

static void
xfs_hole_to_iomap(
        struct xfs_inode        *ip,
        struct iomap            *iomap,
        xfs_fileoff_t           offset_fsb,
        xfs_fileoff_t           end_fsb)
{
        struct xfs_buftarg      *target = xfs_inode_buftarg(ip);

        iomap->addr = IOMAP_NULL_ADDR;
        iomap->type = IOMAP_HOLE;
        iomap->offset = XFS_FSB_TO_B(ip->i_mount, offset_fsb);
        iomap->length = XFS_FSB_TO_B(ip->i_mount, end_fsb - offset_fsb);
        iomap->bdev = target->bt_bdev;
        iomap->dax_dev = target->bt_daxdev;
}

static inline xfs_fileoff_t
xfs_iomap_end_fsb(
        struct xfs_mount        *mp,
        loff_t                  offset,
        loff_t                  count)
{
        ASSERT(offset <= mp->m_super->s_maxbytes);
        return min(XFS_B_TO_FSB(mp, offset + count),
                   XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes));
}

static xfs_extlen_t
xfs_eof_alignment(
        struct xfs_inode        *ip)
{
        struct xfs_mount        *mp = ip->i_mount;
        xfs_extlen_t            align = 0;

        if (!XFS_IS_REALTIME_INODE(ip)) {
                /*
                 * Round up the allocation request to a stripe unit
                 * (m_dalign) boundary if the file size is >= stripe unit
                 * size, and we are allocating past the allocation eof.
                 *
                 * If mounted with the "-o swalloc" option the alignment is
                 * increased from the strip unit size to the stripe width.
                 */
                if (mp->m_swidth && (mp->m_flags & XFS_MOUNT_SWALLOC))
                        align = mp->m_swidth;
                else if (mp->m_dalign)
                        align = mp->m_dalign;

                if (align && XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, align))
                        align = 0;
        }

        return align;
}

/*
 * Check if last_fsb is outside the last extent, and if so grow it to the next
 * stripe unit boundary.
 */
xfs_fileoff_t
xfs_iomap_eof_align_last_fsb(
        struct xfs_inode        *ip,
        xfs_fileoff_t           end_fsb)
{
        struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
        xfs_extlen_t            extsz = xfs_get_extsz_hint(ip);
        xfs_extlen_t            align = xfs_eof_alignment(ip);
        struct xfs_bmbt_irec    irec;
        struct xfs_iext_cursor  icur;

        ASSERT(ifp->if_flags & XFS_IFEXTENTS);

        /*
         * Always round up the allocation request to the extent hint boundary.
         */
        if (extsz) {
                if (align)
                        align = roundup_64(align, extsz);
                else
                        align = extsz;
        }

        if (align) {
                xfs_fileoff_t   aligned_end_fsb = roundup_64(end_fsb, align);

                xfs_iext_last(ifp, &icur);
                if (!xfs_iext_get_extent(ifp, &icur, &irec) ||
                    aligned_end_fsb >= irec.br_startoff + irec.br_blockcount)
                        return aligned_end_fsb;
        }

        return end_fsb;
}

int
xfs_iomap_write_direct(
        struct xfs_inode        *ip,
        xfs_fileoff_t           offset_fsb,
        xfs_fileoff_t           count_fsb,
        struct xfs_bmbt_irec    *imap)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_trans        *tp;
        xfs_filblks_t           resaligned;
        int                     nimaps;
        int                     quota_flag;
        uint                    qblocks, resblks;
        unsigned int            resrtextents = 0;
        int                     error;
        int                     bmapi_flags = XFS_BMAPI_PREALLOC;
        uint                    tflags = 0;

        ASSERT(count_fsb > 0);

        resaligned = xfs_aligned_fsb_count(offset_fsb, count_fsb,
                                           xfs_get_extsz_hint(ip));
        if (unlikely(XFS_IS_REALTIME_INODE(ip))) {
                resrtextents = qblocks = resaligned;
                resrtextents /= mp->m_sb.sb_rextsize;
                resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0);
                quota_flag = XFS_QMOPT_RES_RTBLKS;
        } else {
                resblks = qblocks = XFS_DIOSTRAT_SPACE_RES(mp, resaligned);
                quota_flag = XFS_QMOPT_RES_REGBLKS;
        }

        error = xfs_qm_dqattach(ip);
        if (error)
                return error;

        /*
         * For DAX, we do not allocate unwritten extents, but instead we zero
         * the block before we commit the transaction.  Ideally we'd like to do
         * this outside the transaction context, but if we commit and then crash
         * we may not have zeroed the blocks and this will be exposed on
         * recovery of the allocation. Hence we must zero before commit.
         *
         * Further, if we are mapping unwritten extents here, we need to zero
         * and convert them to written so that we don't need an unwritten extent
         * callback for DAX. This also means that we need to be able to dip into
         * the reserve block pool for bmbt block allocation if there is no space
         * left but we need to do unwritten extent conversion.
         */
        if (IS_DAX(VFS_I(ip))) {
                bmapi_flags = XFS_BMAPI_CONVERT | XFS_BMAPI_ZERO;
                if (imap->br_state == XFS_EXT_UNWRITTEN) {
                        tflags |= XFS_TRANS_RESERVE;
                        resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0) << 1;
                }
        }
        error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, resrtextents,
                        tflags, &tp);
        if (error)
                return error;

        xfs_ilock(ip, XFS_ILOCK_EXCL);

        error = xfs_trans_reserve_quota_nblks(tp, ip, qblocks, 0, quota_flag);
        if (error)
                goto out_trans_cancel;

        xfs_trans_ijoin(tp, ip, 0);

        /*
         * From this point onwards we overwrite the imap pointer that the
         * caller gave to us.
         */
        nimaps = 1;
        error = xfs_bmapi_write(tp, ip, offset_fsb, count_fsb, bmapi_flags, 0,
                                imap, &nimaps);
        if (error)
                goto out_res_cancel;

        /*
         * Complete the transaction
         */
        error = xfs_trans_commit(tp);
        if (error)
                goto out_unlock;

        /*
         * Copy any maps to caller's array and return any error.
         */
        if (nimaps == 0) {
                error = -ENOSPC;
                goto out_unlock;
        }

        if (unlikely(!xfs_valid_startblock(ip, imap->br_startblock)))
                error = xfs_alert_fsblock_zero(ip, imap);

out_unlock:
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        return error;

out_res_cancel:
        xfs_trans_unreserve_quota_nblks(tp, ip, (long)qblocks, 0, quota_flag);
out_trans_cancel:
        xfs_trans_cancel(tp);
        goto out_unlock;
}

STATIC bool
xfs_quota_need_throttle(
        struct xfs_inode *ip,
        int type,
        xfs_fsblock_t alloc_blocks)
{
        struct xfs_dquot *dq = xfs_inode_dquot(ip, type);

        if (!dq || !xfs_this_quota_on(ip->i_mount, type))
                return false;

        /* no hi watermark, no throttle */
        if (!dq->q_prealloc_hi_wmark)
                return false;

        /* under the lo watermark, no throttle */
        if (dq->q_res_bcount + alloc_blocks < dq->q_prealloc_lo_wmark)
                return false;

        return true;
}

STATIC void
xfs_quota_calc_throttle(
        struct xfs_inode *ip,
        int type,
        xfs_fsblock_t *qblocks,
        int *qshift,
        int64_t *qfreesp)
{
        int64_t freesp;
        int shift = 0;
        struct xfs_dquot *dq = xfs_inode_dquot(ip, type);

        /* no dq, or over hi wmark, squash the prealloc completely */
        if (!dq || dq->q_res_bcount >= dq->q_prealloc_hi_wmark) {
                *qblocks = 0;
                *qfreesp = 0;
                return;
        }

        freesp = dq->q_prealloc_hi_wmark - dq->q_res_bcount;
        if (freesp < dq->q_low_space[XFS_QLOWSP_5_PCNT]) {
                shift = 2;
                if (freesp < dq->q_low_space[XFS_QLOWSP_3_PCNT])
                        shift += 2;
                if (freesp < dq->q_low_space[XFS_QLOWSP_1_PCNT])
                        shift += 2;
        }

        if (freesp < *qfreesp)
                *qfreesp = freesp;

        /* only overwrite the throttle values if we are more aggressive */
        if ((freesp >> shift) < (*qblocks >> *qshift)) {
                *qblocks = freesp;
                *qshift = shift;
        }
}

/*
 * If we are doing a write at the end of the file and there are no allocations
 * past this one, then extend the allocation out to the file system's write
 * iosize.
 *
 * If we don't have a user specified preallocation size, dynamically increase
 * the preallocation size as the size of the file grows.  Cap the maximum size
 * at a single extent or less if the filesystem is near full. The closer the
 * filesystem is to full, the smaller the maximum prealocation.
 *
 * As an exception we don't do any preallocation at all if the file is smaller
 * than the minimum preallocation and we are using the default dynamic
 * preallocation scheme, as it is likely this is the only write to the file that
 * is going to be done.
 *
 * We clean up any extra space left over when the file is closed in
 * xfs_inactive().
 */
STATIC xfs_fsblock_t
xfs_iomap_prealloc_size(
        struct xfs_inode        *ip,
        int                     whichfork,
        loff_t                  offset,
        loff_t                  count,
        struct xfs_iext_cursor  *icur)
{
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, whichfork);
        xfs_fileoff_t           offset_fsb = XFS_B_TO_FSBT(mp, offset);
        struct xfs_bmbt_irec    prev;
        int                     shift = 0;
        int64_t                 freesp;
        xfs_fsblock_t           qblocks;
        int                     qshift = 0;
        xfs_fsblock_t           alloc_blocks = 0;

        if (offset + count <= XFS_ISIZE(ip))
                return 0;

        if (!(mp->m_flags & XFS_MOUNT_ALLOCSIZE) &&
            (XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_allocsize_blocks)))
                return 0;

        /*
         * If an explicit allocsize is set, the file is small, or we
         * are writing behind a hole, then use the minimum prealloc:
         */
        if ((mp->m_flags & XFS_MOUNT_ALLOCSIZE) ||
            XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_dalign) ||
            !xfs_iext_peek_prev_extent(ifp, icur, &prev) ||
            prev.br_startoff + prev.br_blockcount < offset_fsb)
                return mp->m_allocsize_blocks;

        /*
         * Determine the initial size of the preallocation. We are beyond the
         * current EOF here, but we need to take into account whether this is
         * a sparse write or an extending write when determining the
         * preallocation size.  Hence we need to look up the extent that ends
         * at the current write offset and use the result to determine the
         * preallocation size.
         *
         * If the extent is a hole, then preallocation is essentially disabled.
         * Otherwise we take the size of the preceding data extent as the basis
         * for the preallocation size. If the size of the extent is greater than
         * half the maximum extent length, then use the current offset as the
         * basis. This ensures that for large files the preallocation size
         * always extends to MAXEXTLEN rather than falling short due to things
         * like stripe unit/width alignment of real extents.
         */
        if (prev.br_blockcount <= (MAXEXTLEN >> 1))
                alloc_blocks = prev.br_blockcount << 1;
        else
                alloc_blocks = XFS_B_TO_FSB(mp, offset);
        if (!alloc_blocks)
                goto check_writeio;
        qblocks = alloc_blocks;

        /*
         * MAXEXTLEN is not a power of two value but we round the prealloc down
         * to the nearest power of two value after throttling. To prevent the
         * round down from unconditionally reducing the maximum supported prealloc
         * size, we round up first, apply appropriate throttling, round down and
         * cap the value to MAXEXTLEN.
         */
        alloc_blocks = XFS_FILEOFF_MIN(roundup_pow_of_two(MAXEXTLEN),
                                       alloc_blocks);

        freesp = percpu_counter_read_positive(&mp->m_fdblocks);
        if (freesp < mp->m_low_space[XFS_LOWSP_5_PCNT]) {
                shift = 2;
                if (freesp < mp->m_low_space[XFS_LOWSP_4_PCNT])
                        shift++;
                if (freesp < mp->m_low_space[XFS_LOWSP_3_PCNT])
                        shift++;
                if (freesp < mp->m_low_space[XFS_LOWSP_2_PCNT])
                        shift++;
                if (freesp < mp->m_low_space[XFS_LOWSP_1_PCNT])
                        shift++;
        }

        /*
         * Check each quota to cap the prealloc size, provide a shift value to
         * throttle with and adjust amount of available space.
         */
        if (xfs_quota_need_throttle(ip, XFS_DQ_USER, alloc_blocks))
                xfs_quota_calc_throttle(ip, XFS_DQ_USER, &qblocks, &qshift,
                                        &freesp);
        if (xfs_quota_need_throttle(ip, XFS_DQ_GROUP, alloc_blocks))
                xfs_quota_calc_throttle(ip, XFS_DQ_GROUP, &qblocks, &qshift,
                                        &freesp);
        if (xfs_quota_need_throttle(ip, XFS_DQ_PROJ, alloc_blocks))
                xfs_quota_calc_throttle(ip, XFS_DQ_PROJ, &qblocks, &qshift,
                                        &freesp);

        /*
         * The final prealloc size is set to the minimum of free space available
         * in each of the quotas and the overall filesystem.
         *
         * The shift throttle value is set to the maximum value as determined by
         * the global low free space values and per-quota low free space values.
         */
        alloc_blocks = min(alloc_blocks, qblocks);
        shift = max(shift, qshift);

        if (shift)
                alloc_blocks >>= shift;
        /*
         * rounddown_pow_of_two() returns an undefined result if we pass in
         * alloc_blocks = 0.
         */
        if (alloc_blocks)
                alloc_blocks = rounddown_pow_of_two(alloc_blocks);
        if (alloc_blocks > MAXEXTLEN)
                alloc_blocks = MAXEXTLEN;

        /*
         * If we are still trying to allocate more space than is
         * available, squash the prealloc hard. This can happen if we
         * have a large file on a small filesystem and the above
         * lowspace thresholds are smaller than MAXEXTLEN.
         */
        while (alloc_blocks && alloc_blocks >= freesp)
                alloc_blocks >>= 4;
check_writeio:
        if (alloc_blocks < mp->m_allocsize_blocks)
                alloc_blocks = mp->m_allocsize_blocks;
        trace_xfs_iomap_prealloc_size(ip, alloc_blocks, shift,
                                      mp->m_allocsize_blocks);
        return alloc_blocks;
}

int
xfs_iomap_write_unwritten(
        xfs_inode_t     *ip,
        xfs_off_t       offset,
        xfs_off_t       count,
        bool            update_isize)
{
        xfs_mount_t     *mp = ip->i_mount;
        xfs_fileoff_t   offset_fsb;
        xfs_filblks_t   count_fsb;
        xfs_filblks_t   numblks_fsb;
        int             nimaps;
        xfs_trans_t     *tp;
        xfs_bmbt_irec_t imap;
        struct inode    *inode = VFS_I(ip);
        xfs_fsize_t     i_size;
        uint            resblks;
        int             error;

        trace_xfs_unwritten_convert(ip, offset, count);

        offset_fsb = XFS_B_TO_FSBT(mp, offset);
        count_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + count);
        count_fsb = (xfs_filblks_t)(count_fsb - offset_fsb);

        /*
         * Reserve enough blocks in this transaction for two complete extent
         * btree splits.  We may be converting the middle part of an unwritten
         * extent and in this case we will insert two new extents in the btree
         * each of which could cause a full split.
         *
         * This reservation amount will be used in the first call to
         * xfs_bmbt_split() to select an AG with enough space to satisfy the
         * rest of the operation.
         */
        resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0) << 1;

        /* Attach dquots so that bmbt splits are accounted correctly. */
        error = xfs_qm_dqattach(ip);
        if (error)
                return error;

        do {
                /*
                 * Set up a transaction to convert the range of extents
                 * from unwritten to real. Do allocations in a loop until
                 * we have covered the range passed in.
                 *
                 * Note that we can't risk to recursing back into the filesystem
                 * here as we might be asked to write out the same inode that we
                 * complete here and might deadlock on the iolock.
                 */
                error = xfs_trans_alloc(mp, &M_RES(mp)->tr_write, resblks, 0,
                                XFS_TRANS_RESERVE, &tp);
                if (error)
                        return error;

                xfs_ilock(ip, XFS_ILOCK_EXCL);
                xfs_trans_ijoin(tp, ip, 0);

                error = xfs_trans_reserve_quota_nblks(tp, ip, resblks, 0,
                                XFS_QMOPT_RES_REGBLKS);
                if (error)
                        goto error_on_bmapi_transaction;

                /*
                 * Modify the unwritten extent state of the buffer.
                 */
                nimaps = 1;
                error = xfs_bmapi_write(tp, ip, offset_fsb, count_fsb,
                                        XFS_BMAPI_CONVERT, resblks, &imap,
                                        &nimaps);
                if (error)
                        goto error_on_bmapi_transaction;

                /*
                 * Log the updated inode size as we go.  We have to be careful
                 * to only log it up to the actual write offset if it is
                 * halfway into a block.
                 */
                i_size = XFS_FSB_TO_B(mp, offset_fsb + count_fsb);
                if (i_size > offset + count)
                        i_size = offset + count;
                if (update_isize && i_size > i_size_read(inode))
                        i_size_write(inode, i_size);
                i_size = xfs_new_eof(ip, i_size);
                if (i_size) {
                        ip->i_d.di_size = i_size;
                        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
                }

                error = xfs_trans_commit(tp);
                xfs_iunlock(ip, XFS_ILOCK_EXCL);
                if (error)
                        return error;

                if (unlikely(!xfs_valid_startblock(ip, imap.br_startblock)))
                        return xfs_alert_fsblock_zero(ip, &imap);

                if ((numblks_fsb = imap.br_blockcount) == 0) {
                        /*
                         * The numblks_fsb value should always get
                         * smaller, otherwise the loop is stuck.
                         */
                        ASSERT(imap.br_blockcount);
                        break;
                }
                offset_fsb += numblks_fsb;
                count_fsb -= numblks_fsb;
        } while (count_fsb > 0);

        return 0;

error_on_bmapi_transaction:
        xfs_trans_cancel(tp);
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        return error;
}

static inline bool
imap_needs_alloc(
        struct inode            *inode,
        unsigned                flags,
        struct xfs_bmbt_irec    *imap,
        int                     nimaps)
{
        /* don't allocate blocks when just zeroing */
        if (flags & IOMAP_ZERO)
                return false;
        if (!nimaps ||
            imap->br_startblock == HOLESTARTBLOCK ||
            imap->br_startblock == DELAYSTARTBLOCK)
                return true;
        /* we convert unwritten extents before copying the data for DAX */
        if (IS_DAX(inode) && imap->br_state == XFS_EXT_UNWRITTEN)
                return true;
        return false;
}

static inline bool
imap_needs_cow(
        struct xfs_inode        *ip,
        unsigned int            flags,
        struct xfs_bmbt_irec    *imap,
        int                     nimaps)
{
        if (!xfs_is_cow_inode(ip))
                return false;

        /* when zeroing we don't have to COW holes or unwritten extents */
        if (flags & IOMAP_ZERO) {
                if (!nimaps ||
                    imap->br_startblock == HOLESTARTBLOCK ||
                    imap->br_state == XFS_EXT_UNWRITTEN)
                        return false;
        }

        return true;
}

static int
xfs_ilock_for_iomap(
        struct xfs_inode        *ip,
        unsigned                flags,
        unsigned                *lockmode)
{
        unsigned                mode = XFS_ILOCK_SHARED;
        bool                    is_write = flags & (IOMAP_WRITE | IOMAP_ZERO);

        /*
         * COW writes may allocate delalloc space or convert unwritten COW
         * extents, so we need to make sure to take the lock exclusively here.
         */
        if (xfs_is_cow_inode(ip) && is_write)
                mode = XFS_ILOCK_EXCL;

        /*
         * Extents not yet cached requires exclusive access, don't block.  This
         * is an opencoded xfs_ilock_data_map_shared() call but with
         * non-blocking behaviour.
         */
        if (!(ip->i_df.if_flags & XFS_IFEXTENTS)) {
                if (flags & IOMAP_NOWAIT)
                        return -EAGAIN;
                mode = XFS_ILOCK_EXCL;
        }

relock:
        if (flags & IOMAP_NOWAIT) {
                if (!xfs_ilock_nowait(ip, mode))
                        return -EAGAIN;
        } else {
                xfs_ilock(ip, mode);
        }

        /*
         * The reflink iflag could have changed since the earlier unlocked
         * check, so if we got ILOCK_SHARED for a write and but we're now a
         * reflink inode we have to switch to ILOCK_EXCL and relock.
         */
        if (mode == XFS_ILOCK_SHARED && is_write && xfs_is_cow_inode(ip)) {
                xfs_iunlock(ip, mode);
                mode = XFS_ILOCK_EXCL;
                goto relock;
        }

        *lockmode = mode;
        return 0;
}

static int
xfs_direct_write_iomap_begin(
        struct inode            *inode,
        loff_t                  offset,
        loff_t                  length,
        unsigned                flags,
        struct iomap            *iomap,
        struct iomap            *srcmap)
{
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_bmbt_irec    imap, cmap;
        xfs_fileoff_t           offset_fsb = XFS_B_TO_FSBT(mp, offset);
        xfs_fileoff_t           end_fsb = xfs_iomap_end_fsb(mp, offset, length);
        int                     nimaps = 1, error = 0;
        bool                    shared = false;
        u16                     iomap_flags = 0;
        unsigned                lockmode;

        ASSERT(flags & (IOMAP_WRITE | IOMAP_ZERO));

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        /*
         * Writes that span EOF might trigger an IO size update on completion,
         * so consider them to be dirty for the purposes of O_DSYNC even if
         * there is no other metadata changes pending or have been made here.
         */
        if (offset + length > i_size_read(inode))
                iomap_flags |= IOMAP_F_DIRTY;

        error = xfs_ilock_for_iomap(ip, flags, &lockmode);
        if (error)
                return error;

        error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
                               &nimaps, 0);
        if (error)
                goto out_unlock;

        if (imap_needs_cow(ip, flags, &imap, nimaps)) {
                error = -EAGAIN;
                if (flags & IOMAP_NOWAIT)
                        goto out_unlock;

                /* may drop and re-acquire the ilock */
                error = xfs_reflink_allocate_cow(ip, &imap, &cmap, &shared,
                                &lockmode, flags & IOMAP_DIRECT);
                if (error)
                        goto out_unlock;
                if (shared)
                        goto out_found_cow;
                end_fsb = imap.br_startoff + imap.br_blockcount;
                length = XFS_FSB_TO_B(mp, end_fsb) - offset;
        }

        if (imap_needs_alloc(inode, flags, &imap, nimaps))
                goto allocate_blocks;

        xfs_iunlock(ip, lockmode);
        trace_xfs_iomap_found(ip, offset, length, XFS_DATA_FORK, &imap);
        return xfs_bmbt_to_iomap(ip, iomap, &imap, iomap_flags);

allocate_blocks:
        error = -EAGAIN;
        if (flags & IOMAP_NOWAIT)
                goto out_unlock;

        /*
         * We cap the maximum length we map to a sane size  to keep the chunks
         * of work done where somewhat symmetric with the work writeback does.
         * This is a completely arbitrary number pulled out of thin air as a
         * best guess for initial testing.
         *
         * Note that the values needs to be less than 32-bits wide until the
         * lower level functions are updated.
         */
        length = min_t(loff_t, length, 1024 * PAGE_SIZE);
        end_fsb = xfs_iomap_end_fsb(mp, offset, length);

        if (offset + length > XFS_ISIZE(ip))
                end_fsb = xfs_iomap_eof_align_last_fsb(ip, end_fsb);
        else if (nimaps && imap.br_startblock == HOLESTARTBLOCK)
                end_fsb = min(end_fsb, imap.br_startoff + imap.br_blockcount);
        xfs_iunlock(ip, lockmode);

        error = xfs_iomap_write_direct(ip, offset_fsb, end_fsb - offset_fsb,
                        &imap);
        if (error)
                return error;

        trace_xfs_iomap_alloc(ip, offset, length, XFS_DATA_FORK, &imap);
        return xfs_bmbt_to_iomap(ip, iomap, &imap, iomap_flags | IOMAP_F_NEW);

out_found_cow:
        xfs_iunlock(ip, lockmode);
        length = XFS_FSB_TO_B(mp, cmap.br_startoff + cmap.br_blockcount);
        trace_xfs_iomap_found(ip, offset, length - offset, XFS_COW_FORK, &cmap);
        if (imap.br_startblock != HOLESTARTBLOCK) {
                error = xfs_bmbt_to_iomap(ip, srcmap, &imap, 0);
                if (error)
                        return error;
        }
        return xfs_bmbt_to_iomap(ip, iomap, &cmap, IOMAP_F_SHARED);

out_unlock:
        xfs_iunlock(ip, lockmode);
        return error;
}

const struct iomap_ops xfs_direct_write_iomap_ops = {
        .iomap_begin            = xfs_direct_write_iomap_begin,
};

static int
xfs_buffered_write_iomap_begin(
        struct inode            *inode,
        loff_t                  offset,
        loff_t                  count,
        unsigned                flags,
        struct iomap            *iomap,
        struct iomap            *srcmap)
{
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        xfs_fileoff_t           offset_fsb = XFS_B_TO_FSBT(mp, offset);
        xfs_fileoff_t           end_fsb = xfs_iomap_end_fsb(mp, offset, count);
        struct xfs_bmbt_irec    imap, cmap;
        struct xfs_iext_cursor  icur, ccur;
        xfs_fsblock_t           prealloc_blocks = 0;
        bool                    eof = false, cow_eof = false, shared = false;
        int                     allocfork = XFS_DATA_FORK;
        int                     error = 0;

        /* we can't use delayed allocations when using extent size hints */
        if (xfs_get_extsz_hint(ip))
                return xfs_direct_write_iomap_begin(inode, offset, count,
                                flags, iomap, srcmap);

        ASSERT(!XFS_IS_REALTIME_INODE(ip));

        xfs_ilock(ip, XFS_ILOCK_EXCL);

        if (XFS_IS_CORRUPT(mp, !xfs_ifork_has_extents(ip, XFS_DATA_FORK)) ||
            XFS_TEST_ERROR(false, mp, XFS_ERRTAG_BMAPIFORMAT)) {
                error = -EFSCORRUPTED;
                goto out_unlock;
        }

        XFS_STATS_INC(mp, xs_blk_mapw);

        if (!(ip->i_df.if_flags & XFS_IFEXTENTS)) {
                error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK);
                if (error)
                        goto out_unlock;
        }

        /*
         * Search the data fork fork first to look up our source mapping.  We
         * always need the data fork map, as we have to return it to the
         * iomap code so that the higher level write code can read data in to
         * perform read-modify-write cycles for unaligned writes.
         */
        eof = !xfs_iext_lookup_extent(ip, &ip->i_df, offset_fsb, &icur, &imap);
        if (eof)
                imap.br_startoff = end_fsb; /* fake hole until the end */

        /* We never need to allocate blocks for zeroing a hole. */
        if ((flags & IOMAP_ZERO) && imap.br_startoff > offset_fsb) {
                xfs_hole_to_iomap(ip, iomap, offset_fsb, imap.br_startoff);
                goto out_unlock;
        }

        /*
         * Search the COW fork extent list even if we did not find a data fork
         * extent.  This serves two purposes: first this implements the
         * speculative preallocation using cowextsize, so that we also unshare
         * block adjacent to shared blocks instead of just the shared blocks
         * themselves.  Second the lookup in the extent list is generally faster
         * than going out to the shared extent tree.
         */
        if (xfs_is_cow_inode(ip)) {
                if (!ip->i_cowfp) {
                        ASSERT(!xfs_is_reflink_inode(ip));
                        xfs_ifork_init_cow(ip);
                }
                cow_eof = !xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb,
                                &ccur, &cmap);
                if (!cow_eof && cmap.br_startoff <= offset_fsb) {
                        trace_xfs_reflink_cow_found(ip, &cmap);
                        goto found_cow;
                }
        }

        if (imap.br_startoff <= offset_fsb) {
                /*
                 * For reflink files we may need a delalloc reservation when
                 * overwriting shared extents.   This includes zeroing of
                 * existing extents that contain data.
                 */
                if (!xfs_is_cow_inode(ip) ||
                    ((flags & IOMAP_ZERO) && imap.br_state != XFS_EXT_NORM)) {
                        trace_xfs_iomap_found(ip, offset, count, XFS_DATA_FORK,
                                        &imap);
                        goto found_imap;
                }

                xfs_trim_extent(&imap, offset_fsb, end_fsb - offset_fsb);

                /* Trim the mapping to the nearest shared extent boundary. */
                error = xfs_bmap_trim_cow(ip, &imap, &shared);
                if (error)
                        goto out_unlock;

                /* Not shared?  Just report the (potentially capped) extent. */
                if (!shared) {
                        trace_xfs_iomap_found(ip, offset, count, XFS_DATA_FORK,
                                        &imap);
                        goto found_imap;
                }

                /*
                 * Fork all the shared blocks from our write offset until the
                 * end of the extent.
                 */
                allocfork = XFS_COW_FORK;
                end_fsb = imap.br_startoff + imap.br_blockcount;
        } else {
                /*
                 * We cap the maximum length we map here to MAX_WRITEBACK_PAGES
                 * pages to keep the chunks of work done where somewhat
                 * symmetric with the work writeback does.  This is a completely
                 * arbitrary number pulled out of thin air.
                 *
                 * Note that the values needs to be less than 32-bits wide until
                 * the lower level functions are updated.
                 */
                count = min_t(loff_t, count, 1024 * PAGE_SIZE);
                end_fsb = xfs_iomap_end_fsb(mp, offset, count);

                if (xfs_is_always_cow_inode(ip))
                        allocfork = XFS_COW_FORK;
        }

        error = xfs_qm_dqattach_locked(ip, false);
        if (error)
                goto out_unlock;

        if (eof) {
                prealloc_blocks = xfs_iomap_prealloc_size(ip, allocfork, offset,
                                count, &icur);
                if (prealloc_blocks) {
                        xfs_extlen_t    align;
                        xfs_off_t       end_offset;
                        xfs_fileoff_t   p_end_fsb;

                        end_offset = XFS_ALLOC_ALIGN(mp, offset + count - 1);
                        p_end_fsb = XFS_B_TO_FSBT(mp, end_offset) +
                                        prealloc_blocks;

                        align = xfs_eof_alignment(ip);
                        if (align)
                                p_end_fsb = roundup_64(p_end_fsb, align);

                        p_end_fsb = min(p_end_fsb,
                                XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes));
                        ASSERT(p_end_fsb > offset_fsb);
                        prealloc_blocks = p_end_fsb - end_fsb;
                }
        }

retry:
        error = xfs_bmapi_reserve_delalloc(ip, allocfork, offset_fsb,
                        end_fsb - offset_fsb, prealloc_blocks,
                        allocfork == XFS_DATA_FORK ? &imap : &cmap,
                        allocfork == XFS_DATA_FORK ? &icur : &ccur,
                        allocfork == XFS_DATA_FORK ? eof : cow_eof);
        switch (error) {
        case 0:
                break;
        case -ENOSPC:
        case -EDQUOT:
                /* retry without any preallocation */
                trace_xfs_delalloc_enospc(ip, offset, count);
                if (prealloc_blocks) {
                        prealloc_blocks = 0;
                        goto retry;
                }
                /*FALLTHRU*/
        default:
                goto out_unlock;
        }

        if (allocfork == XFS_COW_FORK) {
                trace_xfs_iomap_alloc(ip, offset, count, allocfork, &cmap);
                goto found_cow;
        }

        /*
         * Flag newly allocated delalloc blocks with IOMAP_F_NEW so we punch
         * them out if the write happens to fail.
         */
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        trace_xfs_iomap_alloc(ip, offset, count, allocfork, &imap);
        return xfs_bmbt_to_iomap(ip, iomap, &imap, IOMAP_F_NEW);

found_imap:
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        return xfs_bmbt_to_iomap(ip, iomap, &imap, 0);

found_cow:
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        if (imap.br_startoff <= offset_fsb) {
                error = xfs_bmbt_to_iomap(ip, srcmap, &imap, 0);
                if (error)
                        return error;
        } else {
                xfs_trim_extent(&cmap, offset_fsb,
                                imap.br_startoff - offset_fsb);
        }
        return xfs_bmbt_to_iomap(ip, iomap, &cmap, IOMAP_F_SHARED);

out_unlock:
        xfs_iunlock(ip, XFS_ILOCK_EXCL);
        return error;
}

static int
xfs_buffered_write_iomap_end(
        struct inode            *inode,
        loff_t                  offset,
        loff_t                  length,
        ssize_t                 written,
        unsigned                flags,
        struct iomap            *iomap)
{
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        xfs_fileoff_t           start_fsb;
        xfs_fileoff_t           end_fsb;
        int                     error = 0;

        if (iomap->type != IOMAP_DELALLOC)
                return 0;

        /*
         * Behave as if the write failed if drop writes is enabled. Set the NEW
         * flag to force delalloc cleanup.
         */
        if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_DROP_WRITES)) {
                iomap->flags |= IOMAP_F_NEW;
                written = 0;
        }

        /*
         * start_fsb refers to the first unused block after a short write. If
         * nothing was written, round offset down to point at the first block in
         * the range.
         */
        if (unlikely(!written))
                start_fsb = XFS_B_TO_FSBT(mp, offset);
        else
                start_fsb = XFS_B_TO_FSB(mp, offset + written);
        end_fsb = XFS_B_TO_FSB(mp, offset + length);

        /*
         * Trim delalloc blocks if they were allocated by this write and we
         * didn't manage to write the whole range.
         *
         * We don't need to care about racing delalloc as we hold i_mutex
         * across the reserve/allocate/unreserve calls. If there are delalloc
         * blocks in the range, they are ours.
         */
        if ((iomap->flags & IOMAP_F_NEW) && start_fsb < end_fsb) {
                truncate_pagecache_range(VFS_I(ip), XFS_FSB_TO_B(mp, start_fsb),
                                         XFS_FSB_TO_B(mp, end_fsb) - 1);

                error = xfs_bmap_punch_delalloc_range(ip, start_fsb,
                                               end_fsb - start_fsb);
                if (error && !XFS_FORCED_SHUTDOWN(mp)) {
                        xfs_alert(mp, "%s: unable to clean up ino %lld",
                                __func__, ip->i_ino);
                        return error;
                }
        }

        return 0;
}

const struct iomap_ops xfs_buffered_write_iomap_ops = {
        .iomap_begin            = xfs_buffered_write_iomap_begin,
        .iomap_end              = xfs_buffered_write_iomap_end,
};

static int
xfs_read_iomap_begin(
        struct inode            *inode,
        loff_t                  offset,
        loff_t                  length,
        unsigned                flags,
        struct iomap            *iomap,
        struct iomap            *srcmap)
{
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        struct xfs_bmbt_irec    imap;
        xfs_fileoff_t           offset_fsb = XFS_B_TO_FSBT(mp, offset);
        xfs_fileoff_t           end_fsb = xfs_iomap_end_fsb(mp, offset, length);
        int                     nimaps = 1, error = 0;
        bool                    shared = false;
        unsigned                lockmode;

        ASSERT(!(flags & (IOMAP_WRITE | IOMAP_ZERO)));

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        error = xfs_ilock_for_iomap(ip, flags, &lockmode);
        if (error)
                return error;
        error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
                               &nimaps, 0);
        if (!error && (flags & IOMAP_REPORT))
                error = xfs_reflink_trim_around_shared(ip, &imap, &shared);
        xfs_iunlock(ip, lockmode);

        if (error)
                return error;
        trace_xfs_iomap_found(ip, offset, length, XFS_DATA_FORK, &imap);
        return xfs_bmbt_to_iomap(ip, iomap, &imap, shared ? IOMAP_F_SHARED : 0);
}

const struct iomap_ops xfs_read_iomap_ops = {
        .iomap_begin            = xfs_read_iomap_begin,
};

static int
xfs_seek_iomap_begin(
        struct inode            *inode,
        loff_t                  offset,
        loff_t                  length,
        unsigned                flags,
        struct iomap            *iomap,
        struct iomap            *srcmap)
{
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        xfs_fileoff_t           offset_fsb = XFS_B_TO_FSBT(mp, offset);
        xfs_fileoff_t           end_fsb = XFS_B_TO_FSB(mp, offset + length);
        xfs_fileoff_t           cow_fsb = NULLFILEOFF, data_fsb = NULLFILEOFF;
        struct xfs_iext_cursor  icur;
        struct xfs_bmbt_irec    imap, cmap;
        int                     error = 0;
        unsigned                lockmode;

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        lockmode = xfs_ilock_data_map_shared(ip);
        if (!(ip->i_df.if_flags & XFS_IFEXTENTS)) {
                error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK);
                if (error)
                        goto out_unlock;
        }

        if (xfs_iext_lookup_extent(ip, &ip->i_df, offset_fsb, &icur, &imap)) {
                /*
                 * If we found a data extent we are done.
                 */
                if (imap.br_startoff <= offset_fsb)
                        goto done;
                data_fsb = imap.br_startoff;
        } else {
                /*
                 * Fake a hole until the end of the file.
                 */
                data_fsb = xfs_iomap_end_fsb(mp, offset, length);
        }

        /*
         * If a COW fork extent covers the hole, report it - capped to the next
         * data fork extent:
         */
        if (xfs_inode_has_cow_data(ip) &&
            xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &cmap))
                cow_fsb = cmap.br_startoff;
        if (cow_fsb != NULLFILEOFF && cow_fsb <= offset_fsb) {
                if (data_fsb < cow_fsb + cmap.br_blockcount)
                        end_fsb = min(end_fsb, data_fsb);
                xfs_trim_extent(&cmap, offset_fsb, end_fsb);
                error = xfs_bmbt_to_iomap(ip, iomap, &cmap, IOMAP_F_SHARED);
                /*
                 * This is a COW extent, so we must probe the page cache
                 * because there could be dirty page cache being backed
                 * by this extent.
                 */
                iomap->type = IOMAP_UNWRITTEN;
                goto out_unlock;
        }

        /*
         * Else report a hole, capped to the next found data or COW extent.
         */
        if (cow_fsb != NULLFILEOFF && cow_fsb < data_fsb)
                imap.br_blockcount = cow_fsb - offset_fsb;
        else
                imap.br_blockcount = data_fsb - offset_fsb;
        imap.br_startoff = offset_fsb;
        imap.br_startblock = HOLESTARTBLOCK;
        imap.br_state = XFS_EXT_NORM;
done:
        xfs_trim_extent(&imap, offset_fsb, end_fsb);
        error = xfs_bmbt_to_iomap(ip, iomap, &imap, 0);
out_unlock:
        xfs_iunlock(ip, lockmode);
        return error;
}

const struct iomap_ops xfs_seek_iomap_ops = {
        .iomap_begin            = xfs_seek_iomap_begin,
};

static int
xfs_xattr_iomap_begin(
        struct inode            *inode,
        loff_t                  offset,
        loff_t                  length,
        unsigned                flags,
        struct iomap            *iomap,
        struct iomap            *srcmap)
{
        struct xfs_inode        *ip = XFS_I(inode);
        struct xfs_mount        *mp = ip->i_mount;
        xfs_fileoff_t           offset_fsb = XFS_B_TO_FSBT(mp, offset);
        xfs_fileoff_t           end_fsb = XFS_B_TO_FSB(mp, offset + length);
        struct xfs_bmbt_irec    imap;
        int                     nimaps = 1, error = 0;
        unsigned                lockmode;

        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;

        lockmode = xfs_ilock_attr_map_shared(ip);

        /* if there are no attribute fork or extents, return ENOENT */
        if (!XFS_IFORK_Q(ip) || !ip->i_d.di_anextents) {
                error = -ENOENT;
                goto out_unlock;
        }

        ASSERT(ip->i_d.di_aformat != XFS_DINODE_FMT_LOCAL);
        error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
                               &nimaps, XFS_BMAPI_ATTRFORK);
out_unlock:
        xfs_iunlock(ip, lockmode);

        if (error)
                return error;
        ASSERT(nimaps);
        return xfs_bmbt_to_iomap(ip, iomap, &imap, 0);
}

const struct iomap_ops xfs_xattr_iomap_ops = {
        .iomap_begin            = xfs_xattr_iomap_begin,
};