f2fs: Use mapping->gfp_mask to get file cache for writing

f2fs: Use mapping->gfp_mask to get file cache for writing

On 32-bit architectures, when GFP_NOFS is used, the file cache for write
operations cannot be allocated from the highmem and CMA.

Since mapping->gfp_mask is set to GFP_HIGHUSER_MOVABLE during inode
allocation, using mapping_gfp_mask(mapping) as the GFP flag of getting file
cache for writing is more efficient for 32-bit architectures.

Additionally, use FGP_NOFS to avoid potential deadlock issues caused by
GFP_FS in GFP_HIGHUSER_MOVABLE

Signed-off-by: Jiucheng Xu <jiucheng.xu@amlogic.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>