On 10/21/19 2:48 PM, Matthew Bobrowski wrote:
In preparation for porting across the ext4 direct I/O path for reads
and writes over to the iomap infrastructure, split up the IOMAP_WRITE
chunk of code into a separate helper ext4_alloc_iomap(). This way,
when we add the necessary bits for direct I/O, we don't end up with
ext4_iomap_begin() becoming a behemoth twisty maze.
Signed-off-by: Matthew Bobrowski <mbobrowski@xxxxxxxxxxxxxx>
Patch looks good to me. You may add:
Reviewed-by: Ritesh Harjani <riteshh@xxxxxxxxxxxxx>
---
fs/ext4/inode.c | 112 ++++++++++++++++++++++++++----------------------
1 file changed, 60 insertions(+), 52 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 0dd29ae5cc8c..3dc92bd8a944 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3442,6 +3442,62 @@ static void ext4_set_iomap(struct inode *inode, struct iomap *iomap,
}
}
+static int ext4_iomap_alloc(struct inode *inode, struct ext4_map_blocks *map,
+ unsigned int flags)
+{
+ handle_t *handle;
+ u8 blkbits = inode->i_blkbits;
+ int ret, dio_credits, retries = 0;
+
+ /*
+ * Trim the mapping request to the maximum value that we can map at
+ * once for direct I/O.
+ */
+ if (map->m_len > DIO_MAX_BLOCKS)
+ map->m_len = DIO_MAX_BLOCKS;
+ dio_credits = ext4_chunk_trans_blocks(inode, map->m_len);
+
+retry:
+ /*
+ * Either we allocate blocks and then don't get an unwritten extent, so
+ * in that case we have reserved enough credits. Or, the blocks are
+ * already allocated and and unwritten. In that case, the extent
+ * conversion fits into the credits too.
+ */
+ handle = ext4_journal_start(inode, EXT4_HT_MAP_BLOCKS, dio_credits);
+ if (IS_ERR(handle))
+ return PTR_ERR(handle);
+
+ ret = ext4_map_blocks(handle, inode, map, EXT4_GET_BLOCKS_CREATE_ZERO);
+ if (ret < 0)
+ goto journal_stop;
+
+ /*
+ * If we have allocated blocks beyond EOF, we need to ensure that
+ * they're truncated if we crash before updating the inode size
+ * metadata within ext4_iomap_end(). For faults, we don't need to do
+ * that (and cannot due to the orphan list operations needing an
+ * inode_lock()). If we happen to instantiate blocks beyond EOF, it is
+ * because we race with a truncate operation, which already has added
+ * the inode onto the orphan list.
+ */
+ if (!(flags & IOMAP_FAULT) && map->m_lblk + map->m_len >
+ (i_size_read(inode) + (1 << blkbits) - 1) >> blkbits) {
+ int err;
+
+ err = ext4_orphan_add(handle, inode);
+ if (err < 0)
+ ret = err;
+ }
+
+journal_stop:
+ ext4_journal_stop(handle);
+ if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
+ goto retry;
+
+ return ret;
+}
+
static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
unsigned flags, struct iomap *iomap)
{
@@ -3502,62 +3558,14 @@ static int ext4_iomap_begin(struct inode *inode, loff_t offset, loff_t length,
}
}
} else if (flags & IOMAP_WRITE) {
- int dio_credits;
- handle_t *handle;
- int retries = 0;
-
- /* Trim mapping request to maximum we can map at once for DIO */
- if (map.m_len > DIO_MAX_BLOCKS)
- map.m_len = DIO_MAX_BLOCKS;
- dio_credits = ext4_chunk_trans_blocks(inode, map.m_len);
-retry:
- /*
- * Either we allocate blocks and then we don't get unwritten
- * extent so we have reserved enough credits, or the blocks
- * are already allocated and unwritten and in that case
- * extent conversion fits in the credits as well.
- */
- handle = ext4_journal_start(inode, EXT4_HT_MAP_BLOCKS,
- dio_credits);
- if (IS_ERR(handle))
- return PTR_ERR(handle);
-
- ret = ext4_map_blocks(handle, inode, &map,
- EXT4_GET_BLOCKS_CREATE_ZERO);
- if (ret < 0) {
- ext4_journal_stop(handle);
- if (ret == -ENOSPC &&
- ext4_should_retry_alloc(inode->i_sb, &retries))
- goto retry;
- return ret;
- }
-
- /*
- * If we added blocks beyond i_size, we need to make sure they
- * will get truncated if we crash before updating i_size in
- * ext4_iomap_end(). For faults we don't need to do that (and
- * even cannot because for orphan list operations inode_lock is
- * required) - if we happen to instantiate block beyond i_size,
- * it is because we race with truncate which has already added
- * the inode to the orphan list.
- */
- if (!(flags & IOMAP_FAULT) && first_block + map.m_len >
- (i_size_read(inode) + (1 << blkbits) - 1) >> blkbits) {
- int err;
-
- err = ext4_orphan_add(handle, inode);
- if (err < 0) {
- ext4_journal_stop(handle);
- return err;
- }
- }
- ext4_journal_stop(handle);
+ ret = ext4_iomap_alloc(inode, &map, flags);
} else {
ret = ext4_map_blocks(NULL, inode, &map, 0);
- if (ret < 0)
- return ret;
}
+ if (ret < 0)
+ return ret;
+
ext4_set_iomap(inode, iomap, &map, offset, length);
if (delalloc && iomap->type == IOMAP_HOLE)
iomap->type = IOMAP_DELALLOC;
