From d218bee86aa570daae9b3c8dc375ac6110813782 Mon Sep 17 00:00:00 2001 From: Chao Liu Date: Mon, 13 Jun 2022 10:08:00 +0800 Subject: docs: filesystems: f2fs: fix description about compress ioctl Since commit c61404153eb6 ("f2fs: introduce FI_COMPRESS_RELEASED instead of using IMMUTABLE bit"), we no longer use the IMMUTABLE bit to prevent writing data for compression. Let's correct the corresponding documentation. BTW, this patch fixes some alignment issues in the compress metadata layout. Signed-off-by: Chao Liu Link: https://lore.kernel.org/r/20220613020800.3379482-1-chaoliu719@gmail.com Signed-off-by: Jonathan Corbet --- Documentation/filesystems/f2fs.rst | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) (limited to 'Documentation/filesystems/f2fs.rst') diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst index ad8dc8c040a2..98dc24f5c6f0 100644 --- a/Documentation/filesystems/f2fs.rst +++ b/Documentation/filesystems/f2fs.rst @@ -818,10 +818,11 @@ Compression implementation Instead, the main goal is to reduce data writes to flash disk as much as possible, resulting in extending disk life time as well as relaxing IO congestion. Alternatively, we've added ioctl(F2FS_IOC_RELEASE_COMPRESS_BLOCKS) - interface to reclaim compressed space and show it to user after putting the - immutable bit. Immutable bit, after release, it doesn't allow writing/mmaping - on the file, until reserving compressed space via - ioctl(F2FS_IOC_RESERVE_COMPRESS_BLOCKS) or truncating filesize to zero. + interface to reclaim compressed space and show it to user after setting a + special flag to the inode. Once the compressed space is released, the flag + will block writing data to the file until either the compressed space is + reserved via ioctl(F2FS_IOC_RESERVE_COMPRESS_BLOCKS) or the file size is + truncated to zero. Compress metadata layout:: @@ -830,12 +831,12 @@ Compress metadata layout:: | cluster 1 | cluster 2 | ......... | cluster N | +-----------------------------------------------+ . . . . - . . . . + . . . . . Compressed Cluster . . Normal Cluster . +----------+---------+---------+---------+ +---------+---------+---------+---------+ |compr flag| block 1 | block 2 | block 3 | | block 1 | block 2 | block 3 | block 4 | +----------+---------+---------+---------+ +---------+---------+---------+---------+ - . . + . . . . . . +-------------+-------------+----------+----------------------------+ -- cgit v1.2.3