[PATCH 0/2] fs,ext4,jbd2: Specifying write-hint for Ext4 journal

[Kanchan Joshi <joshi.k@samsung.com>]

For NAND-based SSDs, mixing of data with different life-time reduces            
efficiency of garbage-collection. During FS operations, series of journal       
updates will follow/precede series of data/meta updates, causing intermixing    
inside SSD. By passing a write-hint (a.k.a stream) with journal, its writes     
can be isolated from other meta/data writes, leading to performance/endurance   
benefit on multi-stream SSD.                                                    
This is described in greater detail (along with results) in this "FAST 2018"    
paper - https://www.usenix.org/system/files/conference/fast18/fast18-rho.pdf    
                                                                                
This patch is split into two parts. First patch introduces APIs to send         
write-hint with buffer-head. Second one implement "journal_writehint" mount     
option (inspired from "journal_ioprio") in Ext4/JBD2.

Kanchan Joshi (2):
  fs: introduce APIs to enable sending write-hint with buffer-head
  fs/ext4,jbd2: Add support for passing write-hint with journal.

 fs/buffer.c                 | 21 +++++++++++++++++++++
 fs/ext4/super.c             | 33 +++++++++++++++++++++++++++------
 fs/jbd2/commit.c            | 11 +++++++----
 fs/jbd2/journal.c           |  2 +-
 fs/jbd2/revoke.c            |  2 +-
 include/linux/buffer_head.h |  3 +++
 include/linux/jbd2.h        |  7 +++++++
 7 files changed, 67 insertions(+), 12 deletions(-)

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2.7.4