[PATCH v3 5/6] fat: permit to return phy block number by fibmap in fallocated region

From: Namjae Jeon
Date: Wed Dec 25 2013 - 01:32:09 EST


From: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>

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.jeon@xxxxxxxxxxx>
Signed-off-by: Amit Sahrawat <a.sahrawat@xxxxxxxxxxx>
---
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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