From: Namjae Jeon <namjae.j...@samsung.com>

Make the fibmap call the return the proper physical block number for any
offset request in the fallocated range.

Signed-off-by: Namjae Jeon <namjae.j...@samsung.com>
Signed-off-by: Amit Sahrawat <a.sahra...@samsung.com>
---
 fs/fat/cache.c |   13 ++++++++++---
 fs/fat/fat.h   |    3 +++
 fs/fat/inode.c |    3 +++
 3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/fs/fat/cache.c b/fs/fat/cache.c
index a132666..d22c1a2 100644
--- a/fs/fat/cache.c
+++ b/fs/fat/cache.c
@@ -325,19 +325,26 @@ int fat_bmap(struct inode *inode, sector_t sector, 
sector_t *phys,
 
        last_block = (i_size_read(inode) + (blocksize - 1)) >> blocksize_bits;
        if (sector >= last_block) {
-               if (!create)
-                       return 0;
-
                /*
                 * Both ->mmu_private and ->i_disksize can access
                 * on only allocation path. (caller must hold ->i_mutex)
                 */
                last_block = (MSDOS_I(inode)->i_disksize + (blocksize - 1))
                        >> blocksize_bits;
+               if (!create) {
+                       /* Map a block in fallocated region */
+                       if (atomic_read(&MSDOS_I(inode)->beyond_isize))
+                               if (sector < last_block)
+                                       goto out_map_cluster;
+
+                       return 0;
+               }
+
                if (sector >= last_block)
                        return 0;
        }
 
+out_map_cluster:
        cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
        offset  = sector & (sbi->sec_per_clus - 1);
        cluster = fat_bmap_cluster(inode, cluster);
diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index 7b5851f..b884276 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -129,6 +129,9 @@ struct msdos_inode_info {
        struct hlist_node i_dir_hash;   /* hash by i_logstart */
        struct rw_semaphore truncate_lock; /* protect bmap against truncate */
        struct inode vfs_inode;
+
+       /* for getting block number beyond file size in case of fallocate */
+       atomic_t beyond_isize;
 };
 
 struct fat_slot_info {
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 3636617..1c3192b 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -256,7 +256,10 @@ static sector_t _fat_bmap(struct address_space *mapping, 
sector_t block)
 
        /* fat_get_cluster() assumes the requested blocknr isn't truncated. */
        down_read(&MSDOS_I(mapping->host)->truncate_lock);
+       /* To get block number beyond file size in fallocated region */
+       atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 1);
        blocknr = generic_block_bmap(mapping, block, fat_get_block);
+       atomic_set(&MSDOS_I(mapping->host)->beyond_isize, 0);
        up_read(&MSDOS_I(mapping->host)->truncate_lock);
 
        return blocknr;
-- 
1.7.9.5

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