The patch titled
Subject: tmpfs: truncate prealloc blocks past i_size
has been added to the -mm tree. Its filename is
tmpfs-truncate-prealloc-blocks-past-i_size.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/tmpfs-truncate-prealloc-blocks-past-i_size.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/tmpfs-truncate-prealloc-blocks-past-i_size.patch
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------------------------------------------------------
From: Josef Bacik <jbacik@xxxxxx>
Subject: 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 <jbacik@xxxxxx>
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/shmem.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN mm/shmem.c~tmpfs-truncate-prealloc-blocks-past-i_size mm/shmem.c
--- a/mm/shmem.c~tmpfs-truncate-prealloc-blocks-past-i_size
+++ a/mm/shmem.c
@@ -569,7 +569,7 @@ static int shmem_setattr(struct dentry *
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);
_
Patches currently in -mm which might be from jbacik@xxxxxx are
tmpfs-truncate-prealloc-blocks-past-i_size.patch
linux-next.patch
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