Miklos,
This is my 2nd attempt to implement concurrent copy up
in overlayfs (3rd if you count the DCACHE_DELETE_LOCK flop).
It's not tagged as V2, because there is nothing in common
between the previous attempt and this one.
This work is based on Al's suggestion to use O_TMPFILE
for regular files and your very helpful waitqueue patch.
Patches 1-4 implement copy up of regular file using O_TMPFILE.
Since there is more common then different code wrt O_TMPFILE
vs. workdir+rename, I opted to keep ovl_copy_up_one() and
copy_up_one_locked() functions with a few 'if (tmpfile) else'
sprinkled around. It may be better to clone copy_up_one_locked()?
Patch 5 is the waitqueue patch you sent me. My only additions are
init_waitqueue_head() and wake_up_lock(), so I kept you as author.
Patch 6 puts it all together. Once again, in an attempt to keep
more common code, I added a few 'if (tmpfile)' and kept the locking
code generic, by assigning workdir = upperdir. I thought you may not
approve with this trick, but couldn't resist trying.
Beyond this simple test:
$ touch /lower/{empty,4g}
$ truncate -s 4g /lower/4g
$ touch /mnt/4g & # takes a while
$ touch /mnt/empty # exits immediately
$ touch /mnt/4g # blocks until %1 completes and can be interrupted
I also wrote xfstest overlay/021 which exercises concurrent copy up
using 8 processes on 4 directories and 4K files.
Amir.
Amir Goldstein (5):
vfs: create vfs helper vfs_tmpfile()
ovl: check if upperdir fs supports O_TMPFILE
ovl: rearrange code in ovl_copy_up_locked()
ovl: copy up regular file using O_TMPFILE
ovl: concurrent copy up of regular files
Miklos Szeredi (1):
ovl: introduce copy up waitqueue
fs/namei.c | 26 +++++++++-------
fs/overlayfs/copy_up.c | 78 +++++++++++++++++++++++++++++++++++-------------
fs/overlayfs/overlayfs.h | 13 ++++++++
fs/overlayfs/ovl_entry.h | 3 ++
fs/overlayfs/super.c | 11 +++++++
fs/overlayfs/util.c | 68 +++++++++++++++++++++++++++++++++++++++++
include/linux/fs.h | 1 +
7 files changed, 170 insertions(+), 30 deletions(-)
--
2.7.4
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