Patchset to solve the previous found freeze/sysfs deadlock.
Unlike previous pending_changes, which uses transaction commits to
ensure mount option doesn't change during transaction.
This idea is great in concept, but will introduce extra and somewhat
duplicated ro/freeze check, and the original synchronized behavior is
also changed.
[Per-transaction mount option]
This patch use the RCU-like concept, which will copy the mount_opt from
fs_info into btrfs_transaction, and each btrfs_test_opt() for specific
mount option bit(SPACE_CACHE/INODE_MAP_CACHE) should be changed to
btrfs_test_trans_opt().
So mount option during transaction won't be changed, and also, no extra
read_only or freeze check is needed, the commit routine is also
untouched.
[Use VFS protect for sysfs change]
The 1st patch will introduce a new helper function sb_want_write() to
claim write permission to a superblock.
With this, we are able to do write protection like mnt_want_write() but
only needs to ensure that the superblock is writeable.
This also keeps the same synchronized behavior using ioctl, which will
block on frozen fs until it is unfrozen.
Changelog:
v1:
Only use cheap freeze check to avoid deadlock.
v2:
Fix the never changed pending_changes bug and handle transaction in
btrfs_freeze()
Revert sysfs only functions.
v3:
Add atomic mount option change and per-trans mount option.
Revert all pending changes functions.
v4:
Add mnt_want_write() in sysfs handler.
v5:
Change VFS helper name to sb_want_write() and sb_drop_write().
Fix a free-n-use bug where sysfs can start a transaction but
transaction thread is freed before btrfs sysfs interfaces.
v6:
Waiting sb_want_write() will block unmouting the last instance of a
sb.
Several codes style and lock timing fix purposed by David.
v7:
Change from spin_lock+bool+count implement to single atomic implment.
Add check in remount ro case purposed by Miao.
Fix some missing unlock in error handler.
Add vfs internal __sb_(read/write)_down_trylock() helper to replace
old open-codes.
Move the vfs to the 1st patch, making it easier to split the vfs
patch from other btrfs only patches.
Qu Wenruo (9):
vfs: Add sb_want_write() function to grant write access to sb without
the struct file/vfsmount.
Revert "btrfs: add support for processing pending changes" related
commits
btrfs: Make btrfs_parse_options() parse mount option in a atomic way
btrfs: Introduce per-transaction mount_opt to keep mount option
consistent during transaction.
btrfs: Use btrfs_test_trans_opt() to handle SPACE_CACHE if it's under
transaction protect.
btrfs: Use btrfs_test_trans_opt() to handle INODE_CACHE if it's under
transaction protect.
btrfs: Move btrfs_sysfs_remove_one(fs_info) before transcation thread
cleanup.
btrfs: Use sb_want_write() to protect label change.
btrfs: Use sb_want_write() to protect sysfs feature change.
fs/btrfs/ctree.h | 64 +++-----------------
fs/btrfs/disk-io.c | 14 ++---
fs/btrfs/extent-tree.c | 2 +-
fs/btrfs/free-space-cache.c | 2 +-
fs/btrfs/inode-map.c | 5 +-
fs/btrfs/super.c | 139 ++++++++++++++++++++------------------------
fs/btrfs/sysfs.c | 75 ++++++++++++++++--------
fs/btrfs/transaction.c | 43 ++------------
fs/btrfs/transaction.h | 6 +-
fs/internal.h | 25 ++++++++
fs/namespace.c | 70 ++++++++++++++++++++++
fs/super.c | 15 ++++-
include/linux/fs.h | 6 ++
include/linux/mount.h | 2 +
14 files changed, 260 insertions(+), 208 deletions(-)
--
2.2.2
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