Btrfs: Add fallocate support v2

This patch updates btrfs-progs for fallocate support.

fallocate is a little different in Btrfs because we need to tell the
COW system that a given preallocated extent doesn't need to be
cow'd as long as there are no snapshots of it.  This leverages the
-o nodatacow checks.
 
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

1 files changed, 9 insertions, 3 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 65a0583027e9..eb3c12e7beaf 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2015,6 +2015,8 @@ printk("2bad mapping end %Lu cur %Lu\n", end, cur);
                 }
                 bdev = em->bdev;
                 block_start = em->block_start;
+                if (test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
+                        block_start = EXTENT_MAP_HOLE;
                 free_extent_map(em);
                 em = NULL;
 
@@ -2769,14 +2771,18 @@ sector_t extent_bmap(struct address_space *mapping, sector_t iblock,
         struct inode *inode = mapping->host;
         u64 start = iblock << inode->i_blkbits;
         sector_t sector = 0;
+        size_t blksize = (1 << inode->i_blkbits);
         struct extent_map *em;
 
-        em = get_extent(inode, NULL, 0, start, (1 << inode->i_blkbits), 0);
+        lock_extent(&BTRFS_I(inode)->io_tree, start, start + blksize - 1,
+                    GFP_NOFS);
+        em = get_extent(inode, NULL, 0, start, blksize, 0);
+        unlock_extent(&BTRFS_I(inode)->io_tree, start, start + blksize - 1,
+                      GFP_NOFS);
         if (!em || IS_ERR(em))
                 return 0;
 
-        if (em->block_start == EXTENT_MAP_INLINE ||
-            em->block_start == EXTENT_MAP_HOLE)
+        if (em->block_start > EXTENT_MAP_LAST_BYTE)
                 goto out;
 
         sector = (em->block_start + start - em->start) >> inode->i_blkbits;