4 files changed, 181 insertions, 315 deletions

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index b060bca93402..614803bc8a9f 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -1388,7 +1388,7 @@ xfs_bmap_search_multi_extents(
  * Else, *lastxp will be set to the index of the found
  * entry; *gotp will contain the entry.
  */
-STATIC xfs_bmbt_rec_host_t *                 /* pointer to found extent entry */
+xfs_bmbt_rec_host_t *                 /* pointer to found extent entry */
 xfs_bmap_search_extents(
         xfs_inode_t     *ip,            /* incore inode pointer */
         xfs_fileoff_t   bno,            /* block number searched for */
@@ -4074,7 +4074,7 @@ xfs_bmapi_read(
         return 0;
 }
 
-STATIC int
+int
 xfs_bmapi_reserve_delalloc(
         struct xfs_inode        *ip,
         xfs_fileoff_t           aoff,
@@ -4170,91 +4170,6 @@ out_unreserve_quota:
         return error;
 }
 
-/*
- * Map file blocks to filesystem blocks, adding delayed allocations as needed.
- */
-int
-xfs_bmapi_delay(
-        struct xfs_inode        *ip,    /* incore inode */
-        xfs_fileoff_t           bno,    /* starting file offs. mapped */
-        xfs_filblks_t           len,    /* length to map in file */
-        struct xfs_bmbt_irec    *mval,  /* output: map values */
-        int                     *nmap,  /* i/o: mval size/count */
-        int                     flags)  /* XFS_BMAPI_... */
-{
-        struct xfs_mount        *mp = ip->i_mount;
-        struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
-        struct xfs_bmbt_irec    got;    /* current file extent record */
-        struct xfs_bmbt_irec    prev;   /* previous file extent record */
-        xfs_fileoff_t           obno;   /* old block number (offset) */
-        xfs_fileoff_t           end;    /* end of mapped file region */
-        xfs_extnum_t            lastx;  /* last useful extent number */
-        int                     eof;    /* we've hit the end of extents */
-        int                     n = 0;  /* current extent index */
-        int                     error = 0;
-
-        ASSERT(*nmap >= 1);
-        ASSERT(*nmap <= XFS_BMAP_MAX_NMAP);
-        ASSERT(!(flags & ~XFS_BMAPI_ENTIRE));
-        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
-
-        if (unlikely(XFS_TEST_ERROR(
-            (XFS_IFORK_FORMAT(ip, XFS_DATA_FORK) != XFS_DINODE_FMT_EXTENTS &&
-             XFS_IFORK_FORMAT(ip, XFS_DATA_FORK) != XFS_DINODE_FMT_BTREE),
-             mp, XFS_ERRTAG_BMAPIFORMAT, XFS_RANDOM_BMAPIFORMAT))) {
-                XFS_ERROR_REPORT("xfs_bmapi_delay", XFS_ERRLEVEL_LOW, mp);
-                return -EFSCORRUPTED;
-        }
-
-        if (XFS_FORCED_SHUTDOWN(mp))
-                return -EIO;
-
-        XFS_STATS_INC(mp, xs_blk_mapw);
-
-        if (!(ifp->if_flags & XFS_IFEXTENTS)) {
-                error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK);
-                if (error)
-                        return error;
-        }
-
-        xfs_bmap_search_extents(ip, bno, XFS_DATA_FORK, &eof, &lastx, &got, &prev);
-        end = bno + len;
-        obno = bno;
-
-        while (bno < end && n < *nmap) {
-                if (eof || got.br_startoff > bno) {
-                        error = xfs_bmapi_reserve_delalloc(ip, bno, len, &got,
-                                                           &prev, &lastx, eof);
-                        if (error) {
-                                if (n == 0) {
-                                        *nmap = 0;
-                                        return error;
-                                }
-                                break;
-                        }
-                }
-
-                /* set up the extent map to return. */
-                xfs_bmapi_trim_map(mval, &got, &bno, len, obno, end, n, flags);
-                xfs_bmapi_update_map(&mval, &bno, &len, obno, end, &n, flags);
-
-                /* If we're done, stop now. */
-                if (bno >= end || n >= *nmap)
-                        break;
-
-                /* Else go on to the next record. */
-                prev = got;
-                if (++lastx < ifp->if_bytes / sizeof(xfs_bmbt_rec_t))
-                        xfs_bmbt_get_all(xfs_iext_get_ext(ifp, lastx), &got);
-                else
-                        eof = 1;
-        }
-
-        *nmap = n;
-        return 0;
-}
-
-
 static int
 xfs_bmapi_allocate(
         struct xfs_bmalloca     *bma)
diff --git a/fs/xfs/libxfs/xfs_bmap.h b/fs/xfs/libxfs/xfs_bmap.h
index 254034f96941..d66006960fbc 100644
--- a/fs/xfs/libxfs/xfs_bmap.h
+++ b/fs/xfs/libxfs/xfs_bmap.h
@@ -181,9 +181,6 @@ int	xfs_bmap_read_extents(struct xfs_trans *tp, struct xfs_inode *ip,
 int     xfs_bmapi_read(struct xfs_inode *ip, xfs_fileoff_t bno,
                 xfs_filblks_t len, struct xfs_bmbt_irec *mval,
                 int *nmap, int flags);
-int     xfs_bmapi_delay(struct xfs_inode *ip, xfs_fileoff_t bno,
-                xfs_filblks_t len, struct xfs_bmbt_irec *mval,
-                int *nmap, int flags);
 int     xfs_bmapi_write(struct xfs_trans *tp, struct xfs_inode *ip,
                 xfs_fileoff_t bno, xfs_filblks_t len, int flags,
                 xfs_fsblock_t *firstblock, xfs_extlen_t total,
@@ -202,5 +199,12 @@ int	xfs_bmap_shift_extents(struct xfs_trans *tp, struct xfs_inode *ip,
                 struct xfs_defer_ops *dfops, enum shift_direction direction,
                 int num_exts);
 int     xfs_bmap_split_extent(struct xfs_inode *ip, xfs_fileoff_t split_offset);
+struct xfs_bmbt_rec_host *
+        xfs_bmap_search_extents(struct xfs_inode *ip, xfs_fileoff_t bno,
+                int fork, int *eofp, xfs_extnum_t *lastxp,
+                struct xfs_bmbt_irec *gotp, struct xfs_bmbt_irec *prevp);
+int     xfs_bmapi_reserve_delalloc(struct xfs_inode *ip, xfs_fileoff_t aoff,
+                xfs_filblks_t len, struct xfs_bmbt_irec *got,
+                struct xfs_bmbt_irec *prev, xfs_extnum_t *lastx, int eof);
 
 #endif  /* __XFS_BMAP_H__ */
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 918511ae115c..f96c8ffce5f4 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2000-2006 Silicon Graphics, Inc.
+ * Copyright (c) 2016 Christoph Hellwig.
  * All Rights Reserved.
  *
  * This program is free software; you can redistribute it and/or
@@ -42,7 +43,6 @@
 
 #define XFS_WRITEIO_ALIGN(mp,off)       (((off) >> mp->m_writeio_log) \
                                                 << mp->m_writeio_log)
-#define XFS_WRITE_IMAPS         XFS_BMAP_MAX_NMAP
 
 void
 xfs_bmbt_to_iomap(
@@ -311,130 +311,6 @@ out_trans_cancel:
         goto out_unlock;
 }
 
-/*
- * If the caller is doing a write at the end of the file, then extend the
- * allocation out to the file system's write iosize.  We clean up any extra
- * space left over when the file is closed in xfs_inactive().
- *
- * If we find we already have delalloc preallocation beyond EOF, don't do more
- * preallocation as it it not needed.
- */
-STATIC int
-xfs_iomap_eof_want_preallocate(
-        xfs_mount_t     *mp,
-        xfs_inode_t     *ip,
-        xfs_off_t       offset,
-        size_t          count,
-        xfs_bmbt_irec_t *imap,
-        int             nimaps,
-        int             *prealloc)
-{
-        xfs_fileoff_t   start_fsb;
-        xfs_filblks_t   count_fsb;
-        int             n, error, imaps;
-        int             found_delalloc = 0;
-
-        *prealloc = 0;
-        if (offset + count <= XFS_ISIZE(ip))
-                return 0;
-
-        /*
-         * If the file is smaller than the minimum prealloc and we are using
-         * dynamic preallocation, don't do any preallocation at all as it is
-         * likely this is the only write to the file that is going to be done.
-         */
-        if (!(mp->m_flags & XFS_MOUNT_DFLT_IOSIZE) &&
-            XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_writeio_blocks))
-                return 0;
-
-        /*
-         * If there are any real blocks past eof, then don't
-         * do any speculative allocation.
-         */
-        start_fsb = XFS_B_TO_FSBT(mp, ((xfs_ufsize_t)(offset + count - 1)));
-        count_fsb = XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes);
-        while (count_fsb > 0) {
-                imaps = nimaps;
-                error = xfs_bmapi_read(ip, start_fsb, count_fsb, imap, &imaps,
-                                       0);
-                if (error)
-                        return error;
-                for (n = 0; n < imaps; n++) {
-                        if ((imap[n].br_startblock != HOLESTARTBLOCK) &&
-                            (imap[n].br_startblock != DELAYSTARTBLOCK))
-                                return 0;
-                        start_fsb += imap[n].br_blockcount;
-                        count_fsb -= imap[n].br_blockcount;
-
-                        if (imap[n].br_startblock == DELAYSTARTBLOCK)
-                                found_delalloc = 1;
-                }
-        }
-        if (!found_delalloc)
-                *prealloc = 1;
-        return 0;
-}
-
-/*
- * 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 preceeding 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.
- */
-STATIC xfs_fsblock_t
-xfs_iomap_eof_prealloc_initial_size(
-        struct xfs_mount        *mp,
-        struct xfs_inode        *ip,
-        xfs_off_t               offset,
-        xfs_bmbt_irec_t         *imap,
-        int                     nimaps)
-{
-        xfs_fileoff_t   start_fsb;
-        int             imaps = 1;
-        int             error;
-
-        ASSERT(nimaps >= imaps);
-
-        /* if we are using a specific prealloc size, return now */
-        if (mp->m_flags & XFS_MOUNT_DFLT_IOSIZE)
-                return 0;
-
-        /* If the file is small, then use the minimum prealloc */
-        if (XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_dalign))
-                return 0;
-
-        /*
-         * As we write multiple pages, the offset will always align to the
-         * start of a page and hence point to a hole at EOF. i.e. if the size is
-         * 4096 bytes, we only have one block at FSB 0, but XFS_B_TO_FSB(4096)
-         * will return FSB 1. Hence if there are blocks in the file, we want to
-         * point to the block prior to the EOF block and not the hole that maps
-         * directly at @offset.
-         */
-        start_fsb = XFS_B_TO_FSB(mp, offset);
-        if (start_fsb)
-                start_fsb--;
-        error = xfs_bmapi_read(ip, start_fsb, 1, imap, &imaps, XFS_BMAPI_ENTIRE);
-        if (error)
-                return 0;
-
-        ASSERT(imaps == 1);
-        if (imap[0].br_startblock == HOLESTARTBLOCK)
-                return 0;
-        if (imap[0].br_blockcount <= (MAXEXTLEN >> 1))
-                return imap[0].br_blockcount << 1;
-        return XFS_B_TO_FSB(mp, offset);
-}
-
 STATIC bool
 xfs_quota_need_throttle(
         struct xfs_inode *ip,
@@ -496,27 +372,76 @@ xfs_quota_calc_throttle(
 }
 
 /*
+ * 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
+ * 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_mount        *mp,
         struct xfs_inode        *ip,
-        xfs_off_t               offset,
-        struct xfs_bmbt_irec    *imap,
-        int                     nimaps)
+        loff_t                  offset,
+        loff_t                  count,
+        xfs_extnum_t            idx,
+        struct xfs_bmbt_irec    *prev)
 {
-        xfs_fsblock_t           alloc_blocks = 0;
+        struct xfs_mount        *mp = ip->i_mount;
+        xfs_fileoff_t           offset_fsb = XFS_B_TO_FSBT(mp, offset);
         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_DFLT_IOSIZE) &&
+            (XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_writeio_blocks)))
+                return 0;
 
-        alloc_blocks = xfs_iomap_eof_prealloc_initial_size(mp, ip, offset,
-                                                           imap, nimaps);
+        /*
+         * 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_DFLT_IOSIZE) ||
+            XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_dalign) ||
+            idx == 0 ||
+            prev->br_startoff + prev->br_blockcount < offset_fsb)
+                return mp->m_writeio_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;
@@ -587,120 +512,145 @@ xfs_iomap_prealloc_size(
          */
         while (alloc_blocks && alloc_blocks >= freesp)
                 alloc_blocks >>= 4;
-
 check_writeio:
         if (alloc_blocks < mp->m_writeio_blocks)
                 alloc_blocks = mp->m_writeio_blocks;
-
         trace_xfs_iomap_prealloc_size(ip, alloc_blocks, shift,
                                       mp->m_writeio_blocks);
-
         return alloc_blocks;
 }
 
-int
-xfs_iomap_write_delay(
-        xfs_inode_t     *ip,
-        xfs_off_t       offset,
-        size_t          count,
-        xfs_bmbt_irec_t *ret_imap)
+static int
+xfs_file_iomap_begin_delay(
+        struct inode            *inode,
+        loff_t                  offset,
+        loff_t                  count,
+        unsigned                flags,
+        struct iomap            *iomap)
 {
-        xfs_mount_t     *mp = ip->i_mount;
-        xfs_fileoff_t   offset_fsb;
-        xfs_fileoff_t   last_fsb;
-        xfs_off_t       aligned_offset;
-        xfs_fileoff_t   ioalign;
-        xfs_extlen_t    extsz;
-        int             nimaps;
-        xfs_bmbt_irec_t imap[XFS_WRITE_IMAPS];
-        int             prealloc;
-        int             error;
-
-        ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
-
-        /*
-         * Make sure that the dquots are there. This doesn't hold
-         * the ilock across a disk read.
-         */
-        error = xfs_qm_dqattach_locked(ip, 0);
-        if (error)
-                return error;
+        struct xfs_inode        *ip = XFS_I(inode);
+        struct xfs_mount        *mp = ip->i_mount;
+        struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
+        xfs_fileoff_t           offset_fsb = XFS_B_TO_FSBT(mp, offset);
+        xfs_fileoff_t           maxbytes_fsb =
+                XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes);
+        xfs_fileoff_t           end_fsb, orig_end_fsb;
+        int                     error = 0, eof = 0;
+        struct xfs_bmbt_irec    got;
+        struct xfs_bmbt_irec    prev;
+        xfs_extnum_t            idx;
 
-        extsz = xfs_get_extsz_hint(ip);
-        offset_fsb = XFS_B_TO_FSBT(mp, offset);
+        ASSERT(!XFS_IS_REALTIME_INODE(ip));
+        ASSERT(!xfs_get_extsz_hint(ip));
 
-        error = xfs_iomap_eof_want_preallocate(mp, ip, offset, count,
-                                imap, XFS_WRITE_IMAPS, &prealloc);
-        if (error)
-                return error;
+        xfs_ilock(ip, XFS_ILOCK_EXCL);
 
-retry:
-        if (prealloc) {
-                xfs_fsblock_t   alloc_blocks;
+        if (unlikely(XFS_TEST_ERROR(
+            (XFS_IFORK_FORMAT(ip, XFS_DATA_FORK) != XFS_DINODE_FMT_EXTENTS &&
+             XFS_IFORK_FORMAT(ip, XFS_DATA_FORK) != XFS_DINODE_FMT_BTREE),
+             mp, XFS_ERRTAG_BMAPIFORMAT, XFS_RANDOM_BMAPIFORMAT))) {
+                XFS_ERROR_REPORT(__func__, XFS_ERRLEVEL_LOW, mp);
+                error = -EFSCORRUPTED;
+                goto out_unlock;
+        }
 
-                alloc_blocks = xfs_iomap_prealloc_size(mp, ip, offset, imap,
-                                                       XFS_WRITE_IMAPS);
+        XFS_STATS_INC(mp, xs_blk_mapw);
 
-                aligned_offset = XFS_WRITEIO_ALIGN(mp, (offset + count - 1));
-                ioalign = XFS_B_TO_FSBT(mp, aligned_offset);
-                last_fsb = ioalign + alloc_blocks;
-        } else {
-                last_fsb = XFS_B_TO_FSB(mp, ((xfs_ufsize_t)(offset + count)));
+        if (!(ifp->if_flags & XFS_IFEXTENTS)) {
+                error = xfs_iread_extents(NULL, ip, XFS_DATA_FORK);
+                if (error)
+                        goto out_unlock;
         }
 
-        if (prealloc || extsz) {
-                error = xfs_iomap_eof_align_last_fsb(ip, extsz, &last_fsb);
-                if (error)
-                        return error;
+        xfs_bmap_search_extents(ip, offset_fsb, XFS_DATA_FORK, &eof, &idx,
+                        &got, &prev);
+        if (!eof && got.br_startoff <= offset_fsb) {
+                trace_xfs_iomap_found(ip, offset, count, 0, &got);
+                goto done;
         }
 
+        error = xfs_qm_dqattach_locked(ip, 0);
+        if (error)
+                goto out_unlock;
+
         /*
-         * Make sure preallocation does not create extents beyond the range we
-         * actually support in this filesystem.
+         * 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 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.
          */
-        if (last_fsb > XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes))
-                last_fsb = XFS_B_TO_FSB(mp, mp->m_super->s_maxbytes);
+        count = min_t(loff_t, count, 1024 * PAGE_SIZE);
+        end_fsb = orig_end_fsb =
+                min(XFS_B_TO_FSB(mp, offset + count), maxbytes_fsb);
 
-        ASSERT(last_fsb > offset_fsb);
+        if (eof) {
+                xfs_fsblock_t   prealloc_blocks;
 
-        nimaps = XFS_WRITE_IMAPS;
-        error = xfs_bmapi_delay(ip, offset_fsb, last_fsb - offset_fsb,
-                                imap, &nimaps, XFS_BMAPI_ENTIRE);
+                prealloc_blocks =
+                        xfs_iomap_prealloc_size(ip, offset, count, idx, &prev);
+                if (prealloc_blocks) {
+                        xfs_extlen_t    align;
+                        xfs_off_t       end_offset;
+
+                        end_offset = XFS_WRITEIO_ALIGN(mp, offset + count - 1);
+                        end_fsb = XFS_B_TO_FSBT(mp, end_offset) +
+                                prealloc_blocks;
+
+                        align = xfs_eof_alignment(ip, 0);
+                        if (align)
+                                end_fsb = roundup_64(end_fsb, align);
+
+                        end_fsb = min(end_fsb, maxbytes_fsb);
+                        ASSERT(end_fsb > offset_fsb);
+                }
+        }
+
+retry:
+        error = xfs_bmapi_reserve_delalloc(ip, offset_fsb,
+                        end_fsb - offset_fsb, &got,
+                        &prev, &idx, eof);
         switch (error) {
         case 0:
+                break;
         case -ENOSPC:
         case -EDQUOT:
-                break;
-        default:
-                return error;
-        }
-
-        /*
-         * If bmapi returned us nothing, we got either ENOSPC or EDQUOT. Retry
-         * without EOF preallocation.
-         */
-        if (nimaps == 0) {
+                /* retry without any preallocation */
                 trace_xfs_delalloc_enospc(ip, offset, count);
-                if (prealloc) {
-                        prealloc = 0;
-                        error = 0;
+                if (end_fsb != orig_end_fsb) {
+                        end_fsb = orig_end_fsb;
                         goto retry;
                 }
-                return error ? error : -ENOSPC;
+                /*FALLTHRU*/
+        default:
+                goto out_unlock;
         }
 
-        if (!(imap[0].br_startblock || XFS_IS_REALTIME_INODE(ip)))
-                return xfs_alert_fsblock_zero(ip, &imap[0]);
-
         /*
          * Tag the inode as speculatively preallocated so we can reclaim this
          * space on demand, if necessary.
          */
-        if (prealloc)
+        if (end_fsb != orig_end_fsb)
                 xfs_inode_set_eofblocks_tag(ip);
 
-        *ret_imap = imap[0];
-        return 0;
+        trace_xfs_iomap_alloc(ip, offset, count, 0, &got);
+done:
+        if (isnullstartblock(got.br_startblock))
+                got.br_startblock = DELAYSTARTBLOCK;
+
+        if (!got.br_startblock) {
+                error = xfs_alert_fsblock_zero(ip, &got);
+                if (error)
+                        goto out_unlock;
+        }
+
+        xfs_bmbt_to_iomap(ip, iomap, &got);
+
+out_unlock:
+        xfs_iunlock(ip, XFS_ILOCK_EXCL);
+        return error;
 }
 
 /*
@@ -1008,6 +958,11 @@ xfs_file_iomap_begin(
         if (XFS_FORCED_SHUTDOWN(mp))
                 return -EIO;
 
+        if ((flags & IOMAP_WRITE) && !xfs_get_extsz_hint(ip)) {
+                return xfs_file_iomap_begin_delay(inode, offset, length, flags,
+                                iomap);
+        }
+
         xfs_ilock(ip, XFS_ILOCK_EXCL);
 
         ASSERT(offset <= mp->m_super->s_maxbytes);
@@ -1035,19 +990,13 @@ xfs_file_iomap_begin(
                  * the lower level functions are updated.
                  */
                 length = min_t(loff_t, length, 1024 * PAGE_SIZE);
-                if (xfs_get_extsz_hint(ip)) {
-                        /*
-                         * xfs_iomap_write_direct() expects the shared lock. It
-                         * is unlocked on return.
-                         */
-                        xfs_ilock_demote(ip, XFS_ILOCK_EXCL);
-                        error = xfs_iomap_write_direct(ip, offset, length, &imap,
-                                        nimaps);
-                } else {
-                        error = xfs_iomap_write_delay(ip, offset, length, &imap);
-                        xfs_iunlock(ip, XFS_ILOCK_EXCL);
-                }
-
+                /*
+                 * xfs_iomap_write_direct() expects the shared lock. It
+                 * is unlocked on return.
+                 */
+                xfs_ilock_demote(ip, XFS_ILOCK_EXCL);
+                error = xfs_iomap_write_direct(ip, offset, length, &imap,
+                                nimaps);
                 if (error)
                         return error;
 
diff --git a/fs/xfs/xfs_iomap.h b/fs/xfs/xfs_iomap.h
index fb8aca3d69ab..6498be485932 100644
--- a/fs/xfs/xfs_iomap.h
+++ b/fs/xfs/xfs_iomap.h
@@ -25,8 +25,6 @@ struct xfs_bmbt_irec;
 
 int xfs_iomap_write_direct(struct xfs_inode *, xfs_off_t, size_t,
                         struct xfs_bmbt_irec *, int);
-int xfs_iomap_write_delay(struct xfs_inode *, xfs_off_t, size_t,
-                        struct xfs_bmbt_irec *);
 int xfs_iomap_write_allocate(struct xfs_inode *, xfs_off_t,
                         struct xfs_bmbt_irec *);
 int xfs_iomap_write_unwritten(struct xfs_inode *, xfs_off_t, xfs_off_t);