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author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-10-09 19:04:27 +0200 |
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committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2017-12-04 19:52:52 +0100 |
commit | 7088efa9137a15d7d21e3abce73e40c9c8a18d68 (patch) | |
tree | a410e9354ca53593b66a1ca8e34041b7d480aaaa /fs/dcache.c | |
parent | drivers/net/ethernet/qlogic/qed: Fix __qed_spq_block() ordering (diff) | |
download | linux-7088efa9137a15d7d21e3abce73e40c9c8a18d68.tar.xz linux-7088efa9137a15d7d21e3abce73e40c9c8a18d68.zip |
fs/dcache: Use release-acquire for name/length update
The code in __d_alloc() carefully orders filling in the NUL character
of the name (and the length, hash, and the name itself) with assigning
of the name itself. However, prepend_name() does not order the accesses
to the ->name and ->len fields, other than on TSO systems. This commit
therefore replaces prepend_name()'s READ_ONCE() of ->name with an
smp_load_acquire(), which orders against the subsequent READ_ONCE() of
->len. Because READ_ONCE() now incorporates smp_read_barrier_depends(),
prepend_name()'s smp_read_barrier_depends() is removed. Finally,
to save a line, the smp_wmb()/store pair in __d_alloc() is replaced
by smp_store_release().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: <linux-fsdevel@vger.kernel.org>
Diffstat (limited to 'fs/dcache.c')
-rw-r--r-- | fs/dcache.c | 10 |
1 files changed, 3 insertions, 7 deletions
diff --git a/fs/dcache.c b/fs/dcache.c index 5c7df1df81ff..379dce86f001 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1636,8 +1636,7 @@ struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name) dname[name->len] = 0; /* Make sure we always see the terminating NUL character */ - smp_wmb(); - dentry->d_name.name = dname; + smp_store_release(&dentry->d_name.name, dname); /* ^^^ */ dentry->d_lockref.count = 1; dentry->d_flags = 0; @@ -3047,17 +3046,14 @@ static int prepend(char **buffer, int *buflen, const char *str, int namelen) * retry it again when a d_move() does happen. So any garbage in the buffer * due to mismatched pointer and length will be discarded. * - * Data dependency barrier is needed to make sure that we see that terminating - * NUL. Alpha strikes again, film at 11... + * Load acquire is needed to make sure that we see that terminating NUL. */ static int prepend_name(char **buffer, int *buflen, const struct qstr *name) { - const char *dname = READ_ONCE(name->name); + const char *dname = smp_load_acquire(&name->name); /* ^^^ */ u32 dlen = READ_ONCE(name->len); char *p; - smp_read_barrier_depends(); - *buflen -= dlen + 1; if (*buflen < 0) return -ENAMETOOLONG; |