Messages in this thread Patch in this message | | | Date | Tue, 16 Jun 2015 13:07:04 -0700 (PDT) | From | Hugh Dickins <> | Subject | [PATCH] tmpfs: truncate prealloc blocks past i_size |
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From: Josef Bacik <jbacik@fb.com>
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 <jbacik@fb.com> Signed-off-by: Hugh Dickins <hughd@google.com> --- mm/shmem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- 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); -- 1.8.3.1
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