Re: [PATCH v2] f2fs: allocate blocks for pinned file

From: Jaegeuk Kim
Date: Fri Jun 28 2019 - 11:36:18 EST


This patch allows fallocate to allocate physical blocks for pinned file.

Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
---
Documentation/filesystems/f2fs.txt | 25 +++++++++++++++++++++++++
fs/f2fs/file.c | 7 ++++++-
2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/Documentation/filesystems/f2fs.txt b/Documentation/filesystems/f2fs.txt
index bebd1be3ba49..496fa28b2492 100644
--- a/Documentation/filesystems/f2fs.txt
+++ b/Documentation/filesystems/f2fs.txt
@@ -804,3 +804,28 @@ WRITE_LIFE_NOT_SET WARM_DATA WRITE_LIFE_NOT_SET
WRITE_LIFE_NONE " WRITE_LIFE_NONE
WRITE_LIFE_MEDIUM " WRITE_LIFE_MEDIUM
WRITE_LIFE_LONG " WRITE_LIFE_LONG
+
+Fallocate(2) Policy
+-------------------
+
+The default policy follows the below posix rule.
+
+Allocating disk space
+ The default operation (i.e., mode is zero) of fallocate() allocates
+ the disk space within the range specified by offset and len. The
+ file size (as reported by stat(2)) will be changed if offset+len is
+ greater than the file size. Any subregion within the range specified
+ by offset and len that did not contain data before the call will be
+ initialized to zero. This default behavior closely resembles the
+ behavior of the posix_fallocate(3) library function, and is intended
+ as a method of optimally implementing that function.
+
+However, once F2FS receives ioctl(fd, F2FS_IOC_SET_PIN_FILE) in prior to
+fallocate(fd, DEFAULT_MODE), it allocates on-disk blocks addressess having
+zero or random data, which is useful to the below scenario where:
+ 1. create(fd)
+ 2. ioctl(fd, F2FS_IOC_SET_PIN_FILE)
+ 3. fallocate(fd, 0, 0, size)
+ 4. address = fibmap(fd, offset)
+ 5. open(blkdev)
+ 6. write(blkdev, address)
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index e7c368db8185..cdfd4338682d 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1528,7 +1528,12 @@ static int expand_inode_data(struct inode *inode, loff_t offset,
if (off_end)
map.m_len++;

- err = f2fs_map_blocks(inode, &map, 1, F2FS_GET_BLOCK_PRE_AIO);
+ if (f2fs_is_pinned_file(inode))
+ map.m_seg_type = CURSEG_COLD_DATA;
+
+ err = f2fs_map_blocks(inode, &map, 1, (f2fs_is_pinned_file(inode) ?
+ F2FS_GET_BLOCK_PRE_DIO :
+ F2FS_GET_BLOCK_PRE_AIO));
if (err) {
pgoff_t last_off;

--
2.19.0.605.g01d371f741-goog