[RFC PATCH 0/6] exfat: take s_lock in read mode for iomap mapping paths
Chi Zhiling <[email protected]>
| Newsgroups | dev.linux.lists.exfat,org.kernel.vger.linux-kernel |
|---|---|
| Message-ID | <[email protected]> |
From: Chi Zhiling <[email protected]> The iomap mapping paths currently serialize all inode mappings on the sbi->s_lock mutex. This series converts it to an rw_semaphore and takes it in read mode on the mapping paths so that mappings of distinct inodes proceed in parallel. The preceding patches make the paths safe to run concurrently: bitmap_lock covers the allocation state, atomic bit ops cover the volume dirty flag, and the FAT2 mirror copy is serialized against writeback. Same-inode access stays serialized by the exclusive inode_lock; writeback does not hold it but is safe because truncate flushes and truncates the page cache first and cannot run concurrently with writeback. The lock ordering (inode_lock -> s_lock -> bitmap_lock) is unchanged, so no new deadlock scenarios are introduced. A per-inode read-write lock was also considered, but its implementation turned out to be considerably more complex, so this series relaxes the existing s_lock instead. Any suggestions on that approach are welcome. The series passes the xfstests exfat suite. In Unixbench, the fstime-w score improved from 3977196.8 to 4746349.6 (~+19%). Any comments and suggestions are welcome. Chi Zhiling (6): exfat: remove dead hint_bmap updates in I/O and truncate paths exfat: take bitmap_lock at the start of exfat_alloc_cluster() exfat: use atomic bit ops for volume dirty flag exfat: lock FAT2 buffer while copying mirrored FAT entries exfat: convert s_lock mutex to rw_semaphore using write lock exfat: take s_lock in read mode for iomap mapping paths fs/exfat/dir.c | 14 +++++++------- fs/exfat/exfat_fs.h | 5 ++--- fs/exfat/exfat_raw.h | 4 ++-- fs/exfat/fatent.c | 20 +++++++++++++------- fs/exfat/file.c | 8 ++------ fs/exfat/inode.c | 15 +++++---------- fs/exfat/iomap.c | 4 ++-- fs/exfat/namei.c | 26 +++++++++++++------------- fs/exfat/super.c | 42 +++++++++++++++++++++--------------------- 9 files changed, 67 insertions(+), 71 deletions(-) -- 2.53.0