From: Josef Bacik Date: Wed, 24 Jun 2015 23:58:45 +0000 (-0700) Subject: tmpfs: truncate prealloc blocks past i_size X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=afa2db2fb6f15f860069de94a1257db57589fe95;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git tmpfs: truncate prealloc blocks past i_size One of the rocksdb people noticed that when you do something like this fallocate(fd, FALLOC_FL_KEEP_SIZE, 0, 10M) pwrite(fd, buf, 5M, 0) ftruncate(5M) on tmpfs, the file would still take up 10M: which led to super fun issues because we were getting ENOSPC before we thought we should be getting ENOSPC. This patch fixes the problem, and mirrors what all the other fs'es do (and was agreed to be the correct behaviour at LSF). I tested it locally to make sure it worked properly with the following xfs_io -f -c "falloc -k 0 10M" -c "pwrite 0 5M" -c "truncate 5M" file Without the patch we have "Blocks: 20480", with the patch we have the correct value of "Blocks: 10240". Signed-off-by: Josef Bacik Signed-off-by: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/shmem.c b/mm/shmem.c index 3759099d8ce4..4caf8ed24d65 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -569,7 +569,7 @@ static int shmem_setattr(struct dentry *dentry, struct iattr *attr) i_size_write(inode, newsize); inode->i_ctime = inode->i_mtime = CURRENT_TIME; } - if (newsize < oldsize) { + if (newsize <= oldsize) { loff_t holebegin = round_up(newsize, PAGE_SIZE); unmap_mapping_range(inode->i_mapping, holebegin, 0, 1); shmem_truncate_range(inode, newsize, (loff_t)-1);