GFS2: Implement iomap for block_map

This patch implements iomap for block mapping, and switches the
block_map function to use it under the covers.

The additional IOMAP_F_BOUNDARY iomap flag indicates when iomap has
reached a "metadata boundary" and fetching the next mapping is likely to
incur an additional I/O.  This flag is used for setting the bh buffer
boundary flag.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

4 files changed, 276 insertions, 69 deletions

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 03badc8417d7..d5f0d96169c5 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -13,6 +13,7 @@
 #include <linux/blkdev.h>
 #include <linux/gfs2_ondisk.h>
 #include <linux/crc32.h>
+#include <linux/iomap.h>
 
 #include "gfs2.h"
 #include "incore.h"
@@ -505,10 +506,8 @@ static inline unsigned int hptrs(struct gfs2_sbd *sdp, const unsigned int hgt)
  * Returns: errno on error
  */
 
-static int gfs2_bmap_alloc(struct inode *inode, const sector_t lblock,
-                           bool zero_new, struct metapath *mp,
-                           const size_t maxlen, sector_t *dblock,
-                           unsigned *dblks)
+static int gfs2_iomap_alloc(struct inode *inode, struct iomap *iomap,
+                            unsigned flags, struct metapath *mp)
 {
         struct gfs2_inode *ip = GFS2_I(inode);
         struct gfs2_sbd *sdp = GFS2_SB(inode);
@@ -516,36 +515,37 @@ static int gfs2_bmap_alloc(struct inode *inode, const sector_t lblock,
         struct buffer_head *dibh = mp->mp_bh[0];
         u64 bn;
         unsigned n, i, blks, alloced = 0, iblks = 0, branch_start = 0;
+        unsigned dblks = 0;
         unsigned ptrs_per_blk;
         const unsigned end_of_metadata = mp->mp_fheight - 1;
         int ret;
-        int eob = 0;
         enum alloc_state state;
         __be64 *ptr;
         __be64 zero_bn = 0;
+        size_t maxlen = iomap->length >> inode->i_blkbits;
 
         BUG_ON(mp->mp_aheight < 1);
         BUG_ON(dibh == NULL);
 
-        *dblock = 0;
-        *dblks = 0;
         gfs2_trans_add_meta(ip->i_gl, dibh);
 
         if (mp->mp_fheight == mp->mp_aheight) {
                 struct buffer_head *bh;
+                int eob;
+
                 /* Bottom indirect block exists, find unalloced extent size */
                 ptr = metapointer(end_of_metadata, mp);
                 bh = mp->mp_bh[end_of_metadata];
-                *dblks = gfs2_extent_length(bh->b_data, bh->b_size, ptr,
-                                            maxlen, &eob);
-                BUG_ON(*dblks < 1);
+                dblks = gfs2_extent_length(bh->b_data, bh->b_size, ptr,
+                                           maxlen, &eob);
+                BUG_ON(dblks < 1);
                 state = ALLOC_DATA;
         } else {
                 /* Need to allocate indirect blocks */
                 ptrs_per_blk = mp->mp_fheight > 1 ? sdp->sd_inptrs :
                         sdp->sd_diptrs;
-                *dblks = min(maxlen, (size_t)(ptrs_per_blk -
-                                              mp->mp_list[end_of_metadata]));
+                dblks = min(maxlen, (size_t)(ptrs_per_blk -
+                                             mp->mp_list[end_of_metadata]));
                 if (mp->mp_fheight == ip->i_height) {
                         /* Writing into existing tree, extend tree down */
                         iblks = mp->mp_fheight - mp->mp_aheight;
@@ -561,7 +561,7 @@ static int gfs2_bmap_alloc(struct inode *inode, const sector_t lblock,
 
         /* start of the second part of the function (state machine) */
 
-        blks = *dblks + iblks;
+        blks = dblks + iblks;
         i = mp->mp_aheight;
         do {
                 int error;
@@ -618,26 +618,29 @@ static int gfs2_bmap_alloc(struct inode *inode, const sector_t lblock,
                                 break;
                 /* Tree complete, adding data blocks */
                 case ALLOC_DATA:
-                        BUG_ON(n > *dblks);
+                        BUG_ON(n > dblks);
                         BUG_ON(mp->mp_bh[end_of_metadata] == NULL);
                         gfs2_trans_add_meta(ip->i_gl, mp->mp_bh[end_of_metadata]);
-                        *dblks = n;
+                        dblks = n;
                         ptr = metapointer(end_of_metadata, mp);
-                        *dblock = bn;
+                        iomap->addr = bn << inode->i_blkbits;
+                        iomap->flags |= IOMAP_F_NEW;
                         while (n-- > 0)
                                 *ptr++ = cpu_to_be64(bn++);
-                        if (zero_new) {
-                                ret = sb_issue_zeroout(sb, *dblock, *dblks,
-                                                       GFP_NOFS);
+                        if (flags & IOMAP_ZERO) {
+                                ret = sb_issue_zeroout(sb, iomap->addr >> inode->i_blkbits,
+                                                       dblks, GFP_NOFS);
                                 if (ret) {
                                         fs_err(sdp,
                                                "Failed to zero data buffers\n");
+                                        flags &= ~IOMAP_ZERO;
                                 }
                         }
                         break;
                 }
-        } while ((state != ALLOC_DATA) || !(*dblock));
+        } while (iomap->addr == IOMAP_NULL_ADDR);
 
+        iomap->length = (u64)dblks << inode->i_blkbits;
         ip->i_height = mp->mp_fheight;
         gfs2_add_inode_blocks(&ip->i_inode, alloced);
         gfs2_dinode_out(ip, mp->mp_bh[0]->b_data);
@@ -645,47 +648,123 @@ static int gfs2_bmap_alloc(struct inode *inode, const sector_t lblock,
 }
 
 /**
- * gfs2_block_map - Map a block from an inode to a disk block
+ * hole_size - figure out the size of a hole
  * @inode: The inode
- * @lblock: The logical block number
- * @bh_map: The bh to be mapped
- * @create: True if its ok to alloc blocks to satify the request
+ * @lblock: The logical starting block number
+ * @mp: The metapath
  *
- * Sets buffer_mapped() if successful, sets buffer_boundary() if a
- * read of metadata will be required before the next block can be
- * mapped. Sets buffer_new() if new blocks were allocated.
+ * Returns: The hole size in bytes
  *
- * Returns: errno
  */
+static u64 hole_size(struct inode *inode, sector_t lblock, struct metapath *mp)
+{
+        struct gfs2_inode *ip = GFS2_I(inode);
+        struct gfs2_sbd *sdp = GFS2_SB(inode);
+        struct metapath mp_eof;
+        u64 factor = 1;
+        int hgt;
+        u64 holesz = 0;
+        const __be64 *first, *end, *ptr;
+        const struct buffer_head *bh;
+        u64 lblock_stop = (i_size_read(inode) - 1) >> inode->i_blkbits;
+        int zeroptrs;
+        bool done = false;
+
+        /* Get another metapath, to the very last byte */
+        find_metapath(sdp, lblock_stop, &mp_eof, ip->i_height);
+        for (hgt = ip->i_height - 1; hgt >= 0 && !done; hgt--) {
+                bh = mp->mp_bh[hgt];
+                if (bh) {
+                        zeroptrs = 0;
+                        first = metapointer(hgt, mp);
+                        end = (const __be64 *)(bh->b_data + bh->b_size);
+
+                        for (ptr = first; ptr < end; ptr++) {
+                                if (*ptr) {
+                                        done = true;
+                                        break;
+                                } else {
+                                        zeroptrs++;
+                                }
+                        }
+                } else {
+                        zeroptrs = sdp->sd_inptrs;
+                }
+                if (factor * zeroptrs >= lblock_stop - lblock + 1) {
+                        holesz = lblock_stop - lblock + 1;
+                        break;
+                }
+                holesz += factor * zeroptrs;
 
-int gfs2_block_map(struct inode *inode, sector_t lblock,
-                   struct buffer_head *bh_map, int create)
+                factor *= sdp->sd_inptrs;
+                if (hgt && (mp->mp_list[hgt - 1] < mp_eof.mp_list[hgt - 1]))
+                        (mp->mp_list[hgt - 1])++;
+        }
+        return holesz << inode->i_blkbits;
+}
+
+static void gfs2_stuffed_iomap(struct inode *inode, struct iomap *iomap)
+{
+        struct gfs2_inode *ip = GFS2_I(inode);
+
+        iomap->addr = (ip->i_no_addr << inode->i_blkbits) +
+                      sizeof(struct gfs2_dinode);
+        iomap->offset = 0;
+        iomap->length = i_size_read(inode);
+        iomap->type = IOMAP_MAPPED;
+        iomap->flags = IOMAP_F_DATA_INLINE;
+}
+
+/**
+ * gfs2_iomap_begin - Map blocks from an inode to disk blocks
+ * @inode: The inode
+ * @pos: Starting position in bytes
+ * @length: Length to map, in bytes
+ * @flags: iomap flags
+ * @iomap: The iomap structure
+ *
+ * Returns: errno
+ */
+int gfs2_iomap_begin(struct inode *inode, loff_t pos, loff_t length,
+                     unsigned flags, struct iomap *iomap)
 {
         struct gfs2_inode *ip = GFS2_I(inode);
         struct gfs2_sbd *sdp = GFS2_SB(inode);
+        struct metapath mp = { .mp_aheight = 1, };
         unsigned int factor = sdp->sd_sb.sb_bsize;
-        const size_t maxlen = bh_map->b_size >> inode->i_blkbits;
         const u64 *arr = sdp->sd_heightsize;
         __be64 *ptr;
-        u64 size;
-        struct metapath mp;
+        sector_t lblock;
+        sector_t lend;
         int ret;
         int eob;
         unsigned int len;
         struct buffer_head *bh;
         u8 height;
-        bool zero_new = false;
-        sector_t dblock = 0;
-        unsigned dblks;
 
-        BUG_ON(maxlen == 0);
+        trace_gfs2_iomap_start(ip, pos, length, flags);
+        if (!length) {
+                ret = -EINVAL;
+                goto out;
+        }
 
-        memset(&mp, 0, sizeof(mp));
-        bmap_lock(ip, create);
-        clear_buffer_mapped(bh_map);
-        clear_buffer_new(bh_map);
-        clear_buffer_boundary(bh_map);
-        trace_gfs2_bmap(ip, bh_map, lblock, create, 1);
+        if ((flags & IOMAP_REPORT) && gfs2_is_stuffed(ip)) {
+                gfs2_stuffed_iomap(inode, iomap);
+                if (pos >= iomap->length)
+                        return -ENOENT;
+                ret = 0;
+                goto out;
+        }
+
+        lblock = pos >> inode->i_blkbits;
+        lend = (pos + length + sdp->sd_sb.sb_bsize - 1) >> inode->i_blkbits;
+
+        iomap->offset = lblock << inode->i_blkbits;
+        iomap->addr = IOMAP_NULL_ADDR;
+        iomap->type = IOMAP_HOLE;
+        iomap->length = (u64)(lend - lblock) << inode->i_blkbits;
+        iomap->flags = IOMAP_F_MERGED;
+        bmap_lock(ip, 0);
 
         /*
          * Directory data blocks have a struct gfs2_meta_header header, so the
@@ -699,56 +778,114 @@ int gfs2_block_map(struct inode *inode, sector_t lblock,
 
         ret = gfs2_meta_inode_buffer(ip, &mp.mp_bh[0]);
         if (ret)
-                goto out;
+                goto out_release;
 
         height = ip->i_height;
-        size = (lblock + 1) * factor;
-        while (size > arr[height])
+        while ((lblock + 1) * factor > arr[height])
                 height++;
         find_metapath(sdp, lblock, &mp, height);
-        mp.mp_aheight = 1;
         if (height > ip->i_height || gfs2_is_stuffed(ip))
                 goto do_alloc;
+
         ret = lookup_metapath(ip, &mp);
         if (ret < 0)
-                goto out;
+                goto out_release;
+
         if (mp.mp_aheight != ip->i_height)
                 goto do_alloc;
+
         ptr = metapointer(ip->i_height - 1, &mp);
         if (*ptr == 0)
                 goto do_alloc;
-        map_bh(bh_map, inode->i_sb, be64_to_cpu(*ptr));
+
+        iomap->type = IOMAP_MAPPED;
+        iomap->addr = be64_to_cpu(*ptr) << inode->i_blkbits;
+
         bh = mp.mp_bh[ip->i_height - 1];
-        len = gfs2_extent_length(bh->b_data, bh->b_size, ptr, maxlen, &eob);
-        bh_map->b_size = (len << inode->i_blkbits);
+        len = gfs2_extent_length(bh->b_data, bh->b_size, ptr, lend - lblock, &eob);
         if (eob)
-                set_buffer_boundary(bh_map);
+                iomap->flags |= IOMAP_F_BOUNDARY;
+        iomap->length = (u64)len << inode->i_blkbits;
+
         ret = 0;
-out:
+
+out_release:
         release_metapath(&mp);
-        trace_gfs2_bmap(ip, bh_map, lblock, create, ret);
-        bmap_unlock(ip, create);
+        bmap_unlock(ip, 0);
+out:
+        trace_gfs2_iomap_end(ip, iomap, ret);
         return ret;
 
 do_alloc:
-        /* All allocations are done here, firstly check create flag */
-        if (!create) {
-                BUG_ON(gfs2_is_stuffed(ip));
+        if (!(flags & IOMAP_WRITE)) {
+                if (pos >= i_size_read(inode)) {
+                        ret = -ENOENT;
+                        goto out_release;
+                }
                 ret = 0;
-                goto out;
+                iomap->length = hole_size(inode, lblock, &mp);
+                goto out_release;
         }
 
-        /* At this point ret is the tree depth of already allocated blocks */
+        ret = gfs2_iomap_alloc(inode, iomap, flags, &mp);
+        goto out_release;
+}
+
+/**
+ * gfs2_block_map - Map a block from an inode to a disk block
+ * @inode: The inode
+ * @lblock: The logical block number
+ * @bh_map: The bh to be mapped
+ * @create: True if its ok to alloc blocks to satify the request
+ *
+ * Sets buffer_mapped() if successful, sets buffer_boundary() if a
+ * read of metadata will be required before the next block can be
+ * mapped. Sets buffer_new() if new blocks were allocated.
+ *
+ * Returns: errno
+ */
+
+int gfs2_block_map(struct inode *inode, sector_t lblock,
+                   struct buffer_head *bh_map, int create)
+{
+        struct gfs2_inode *ip = GFS2_I(inode);
+        struct iomap iomap;
+        int ret, flags = 0;
+
+        clear_buffer_mapped(bh_map);
+        clear_buffer_new(bh_map);
+        clear_buffer_boundary(bh_map);
+        trace_gfs2_bmap(ip, bh_map, lblock, create, 1);
+
+        if (create)
+                flags |= IOMAP_WRITE;
         if (buffer_zeronew(bh_map))
-                zero_new = true;
-        ret = gfs2_bmap_alloc(inode, lblock, zero_new, &mp, maxlen, &dblock,
-                              &dblks);
-        if (ret == 0) {
-                map_bh(bh_map, inode->i_sb, dblock);
-                bh_map->b_size = dblks << inode->i_blkbits;
-                set_buffer_new(bh_map);
+                flags |= IOMAP_ZERO;
+        ret = gfs2_iomap_begin(inode, (loff_t)lblock << inode->i_blkbits,
+                               bh_map->b_size, flags, &iomap);
+        if (ret) {
+                if (!create && ret == -ENOENT) {
+                        /* Return unmapped buffer beyond the end of file.  */
+                        ret = 0;
+                }
+                goto out;
+        }
+
+        if (iomap.length > bh_map->b_size) {
+                iomap.length = bh_map->b_size;
+                iomap.flags &= ~IOMAP_F_BOUNDARY;
         }
-        goto out;
+        if (iomap.addr != IOMAP_NULL_ADDR)
+                map_bh(bh_map, inode->i_sb, iomap.addr >> inode->i_blkbits);
+        bh_map->b_size = iomap.length;
+        if (iomap.flags & IOMAP_F_BOUNDARY)
+                set_buffer_boundary(bh_map);
+        if (iomap.flags & IOMAP_F_NEW)
+                set_buffer_new(bh_map);
+
+out:
+        trace_gfs2_bmap(ip, bh_map, lblock, create, ret);
+        return ret;
 }
 
 /*
diff --git a/fs/gfs2/bmap.h b/fs/gfs2/bmap.h
index 81ded5e2aaa2..443cc182cf18 100644
--- a/fs/gfs2/bmap.h
+++ b/fs/gfs2/bmap.h
@@ -10,6 +10,8 @@
 #ifndef __BMAP_DOT_H__
 #define __BMAP_DOT_H__
 
+#include <linux/iomap.h>
+
 #include "inode.h"
 
 struct inode;
@@ -47,6 +49,8 @@ static inline void gfs2_write_calc_reserv(const struct gfs2_inode *ip,
 extern int gfs2_unstuff_dinode(struct gfs2_inode *ip, struct page *page);
 extern int gfs2_block_map(struct inode *inode, sector_t lblock,
                           struct buffer_head *bh, int create);
+extern int gfs2_iomap_begin(struct inode *inode, loff_t pos, loff_t length,
+                            unsigned flags, struct iomap *iomap);
 extern int gfs2_extent_map(struct inode *inode, u64 lblock, int *new,
                            u64 *dblock, unsigned *extlen);
 extern int gfs2_setattr_size(struct inode *inode, u64 size);
diff --git a/fs/gfs2/trace_gfs2.h b/fs/gfs2/trace_gfs2.h
index 49ac55da4e33..3c91ae3cf0b2 100644
--- a/fs/gfs2/trace_gfs2.h
+++ b/fs/gfs2/trace_gfs2.h
@@ -12,6 +12,7 @@
 #include <linux/gfs2_ondisk.h>
 #include <linux/writeback.h>
 #include <linux/ktime.h>
+#include <linux/iomap.h>
 #include "incore.h"
 #include "glock.h"
 #include "rgrp.h"
@@ -469,6 +470,70 @@ TRACE_EVENT(gfs2_bmap,
                   __entry->errno)
 );
 
+TRACE_EVENT(gfs2_iomap_start,
+
+        TP_PROTO(const struct gfs2_inode *ip, loff_t pos, ssize_t length,
+                 u16 flags),
+
+        TP_ARGS(ip, pos, length, flags),
+
+        TP_STRUCT__entry(
+                __field(        dev_t,  dev                     )
+                __field(        u64,    inum                    )
+                __field(        loff_t, pos                     )
+                __field(        ssize_t, length                 )
+                __field(        u16,    flags                   )
+        ),
+
+        TP_fast_assign(
+                __entry->dev            = ip->i_gl->gl_name.ln_sbd->sd_vfs->s_dev;
+                __entry->inum           = ip->i_no_addr;
+                __entry->pos            = pos;
+                __entry->length         = length;
+                __entry->flags          = flags;
+        ),
+
+        TP_printk("%u,%u bmap %llu iomap start %llu/%lu flags:%08x",
+                  MAJOR(__entry->dev), MINOR(__entry->dev),
+                  (unsigned long long)__entry->inum,
+                  (unsigned long long)__entry->pos,
+                  (unsigned long)__entry->length, (u16)__entry->flags)
+);
+
+TRACE_EVENT(gfs2_iomap_end,
+
+        TP_PROTO(const struct gfs2_inode *ip, struct iomap *iomap, int ret),
+
+        TP_ARGS(ip, iomap, ret),
+
+        TP_STRUCT__entry(
+                __field(        dev_t,  dev                     )
+                __field(        u64,    inum                    )
+                __field(        loff_t, offset                  )
+                __field(        ssize_t, length                 )
+                __field(        u16,    flags                   )
+                __field(        u16,    type                    )
+                __field(        int,    ret                     )
+        ),
+
+        TP_fast_assign(
+                __entry->dev            = ip->i_gl->gl_name.ln_sbd->sd_vfs->s_dev;
+                __entry->inum           = ip->i_no_addr;
+                __entry->offset         = iomap->offset;
+                __entry->length         = iomap->length;
+                __entry->flags          = iomap->flags;
+                __entry->type           = iomap->type;
+                __entry->ret            = ret;
+        ),
+
+        TP_printk("%u,%u bmap %llu iomap end %llu/%lu ty:%d flags:%08x rc:%d",
+                  MAJOR(__entry->dev), MINOR(__entry->dev),
+                  (unsigned long long)__entry->inum,
+                  (unsigned long long)__entry->offset,
+                  (unsigned long)__entry->length, (u16)__entry->type,
+                  (u16)__entry->flags, __entry->ret)
+);
+
 /* Keep track of blocks as they are allocated/freed */
 TRACE_EVENT(gfs2_block_alloc,
 
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 2b0790dbd6ea..a61be86710b5 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -21,7 +21,8 @@ struct vm_fault;
 /*
  * Flags for all iomap mappings:
  */
-#define IOMAP_F_NEW     0x01    /* blocks have been newly allocated */
+#define IOMAP_F_NEW             0x01    /* blocks have been newly allocated */
+#define IOMAP_F_BOUNDARY        0x02    /* mapping ends at metadata boundary */
 
 /*
  * Flags that only need to be reported for IOMAP_REPORT requests: