diff options
| author | Jaegeuk Kim <jaegeuk@kernel.org> | 2019-06-27 03:23:05 +0200 |
|---|---|---|
| committer | Jaegeuk Kim <jaegeuk@kernel.org> | 2019-07-03 00:40:42 +0200 |
| commit | cad3836f9eb292647c9e3e5c6c778e6fa6e6bf15 (patch) | |
| tree | d2dfb3cfe303ed1bb3f4d834d964e6a60872cfad /Documentation | |
| parent | f2fs: fix is_idle() check for discard type (diff) | |
| download | linux-cad3836f9eb292647c9e3e5c6c778e6fa6e6bf15.tar.xz linux-cad3836f9eb292647c9e3e5c6c778e6fa6e6bf15.zip | |
f2fs: allocate blocks for pinned file
This patch allows fallocate to allocate physical blocks for pinned file.
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/filesystems/f2fs.txt | 25 |
1 files changed, 25 insertions, 0 deletions
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) |