From 621e155a3591962420eacdd39f6f0aa29ceb221e Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Fri, 7 Jan 2011 17:49:27 +1100 Subject: fs: change d_compare for rcu-walk Change d_compare so it may be called from lock-free RCU lookups. This does put significant restrictions on what may be done from the callback, however there don't seem to have been any problems with in-tree fses. If some strange use case pops up that _really_ cannot cope with the rcu-walk rules, we can just add new rcu-unaware callbacks, which would cause name lookup to drop out of rcu-walk mode. For in-tree filesystems, this is just a mechanical change. Signed-off-by: Nick Piggin --- fs/isofs/inode.c | 92 +++++++++++++++++++++++++++++--------------------------- fs/isofs/namei.c | 3 +- 2 files changed, 49 insertions(+), 46 deletions(-) (limited to 'fs/isofs') diff --git a/fs/isofs/inode.c b/fs/isofs/inode.c index bfdeb82a53b..7b0fbc61af8 100644 --- a/fs/isofs/inode.c +++ b/fs/isofs/inode.c @@ -28,14 +28,26 @@ static int isofs_hashi(struct dentry *parent, struct qstr *qstr); static int isofs_hash(struct dentry *parent, struct qstr *qstr); -static int isofs_dentry_cmpi(struct dentry *dentry, struct qstr *a, struct qstr *b); -static int isofs_dentry_cmp(struct dentry *dentry, struct qstr *a, struct qstr *b); +static int isofs_dentry_cmpi(const struct dentry *parent, + const struct inode *pinode, + const struct dentry *dentry, const struct inode *inode, + unsigned int len, const char *str, const struct qstr *name); +static int isofs_dentry_cmp(const struct dentry *parent, + const struct inode *pinode, + const struct dentry *dentry, const struct inode *inode, + unsigned int len, const char *str, const struct qstr *name); #ifdef CONFIG_JOLIET static int isofs_hashi_ms(struct dentry *parent, struct qstr *qstr); static int isofs_hash_ms(struct dentry *parent, struct qstr *qstr); -static int isofs_dentry_cmpi_ms(struct dentry *dentry, struct qstr *a, struct qstr *b); -static int isofs_dentry_cmp_ms(struct dentry *dentry, struct qstr *a, struct qstr *b); +static int isofs_dentry_cmpi_ms(const struct dentry *parent, + const struct inode *pinode, + const struct dentry *dentry, const struct inode *inode, + unsigned int len, const char *str, const struct qstr *name); +static int isofs_dentry_cmp_ms(const struct dentry *parent, + const struct inode *pinode, + const struct dentry *dentry, const struct inode *inode, + unsigned int len, const char *str, const struct qstr *name); #endif static void isofs_put_super(struct super_block *sb) @@ -206,49 +218,31 @@ isofs_hashi_common(struct dentry *dentry, struct qstr *qstr, int ms) } /* - * Case insensitive compare of two isofs names. + * Compare of two isofs names. */ -static int isofs_dentry_cmpi_common(struct dentry *dentry, struct qstr *a, - struct qstr *b, int ms) +static int isofs_dentry_cmp_common( + unsigned int len, const char *str, + const struct qstr *name, int ms, int ci) { int alen, blen; /* A filename cannot end in '.' or we treat it like it has none */ - alen = a->len; - blen = b->len; + alen = name->len; + blen = len; if (ms) { - while (alen && a->name[alen-1] == '.') + while (alen && name->name[alen-1] == '.') alen--; - while (blen && b->name[blen-1] == '.') + while (blen && str[blen-1] == '.') blen--; } if (alen == blen) { - if (strnicmp(a->name, b->name, alen) == 0) - return 0; - } - return 1; -} - -/* - * Case sensitive compare of two isofs names. - */ -static int isofs_dentry_cmp_common(struct dentry *dentry, struct qstr *a, - struct qstr *b, int ms) -{ - int alen, blen; - - /* A filename cannot end in '.' or we treat it like it has none */ - alen = a->len; - blen = b->len; - if (ms) { - while (alen && a->name[alen-1] == '.') - alen--; - while (blen && b->name[blen-1] == '.') - blen--; - } - if (alen == blen) { - if (strncmp(a->name, b->name, alen) == 0) - return 0; + if (ci) { + if (strnicmp(name->name, str, alen) == 0) + return 0; + } else { + if (strncmp(name->name, str, alen) == 0) + return 0; + } } return 1; } @@ -266,15 +260,19 @@ isofs_hashi(struct dentry *dentry, struct qstr *qstr) } static int -isofs_dentry_cmp(struct dentry *dentry,struct qstr *a,struct qstr *b) +isofs_dentry_cmp(const struct dentry *parent, const struct inode *pinode, + const struct dentry *dentry, const struct inode *inode, + unsigned int len, const char *str, const struct qstr *name) { - return isofs_dentry_cmp_common(dentry, a, b, 0); + return isofs_dentry_cmp_common(len, str, name, 0, 0); } static int -isofs_dentry_cmpi(struct dentry *dentry,struct qstr *a,struct qstr *b) +isofs_dentry_cmpi(const struct dentry *parent, const struct inode *pinode, + const struct dentry *dentry, const struct inode *inode, + unsigned int len, const char *str, const struct qstr *name) { - return isofs_dentry_cmpi_common(dentry, a, b, 0); + return isofs_dentry_cmp_common(len, str, name, 0, 1); } #ifdef CONFIG_JOLIET @@ -291,15 +289,19 @@ isofs_hashi_ms(struct dentry *dentry, struct qstr *qstr) } static int -isofs_dentry_cmp_ms(struct dentry *dentry,struct qstr *a,struct qstr *b) +isofs_dentry_cmp_ms(const struct dentry *parent, const struct inode *pinode, + const struct dentry *dentry, const struct inode *inode, + unsigned int len, const char *str, const struct qstr *name) { - return isofs_dentry_cmp_common(dentry, a, b, 1); + return isofs_dentry_cmp_common(len, str, name, 1, 0); } static int -isofs_dentry_cmpi_ms(struct dentry *dentry,struct qstr *a,struct qstr *b) +isofs_dentry_cmpi_ms(const struct dentry *parent, const struct inode *pinode, + const struct dentry *dentry, const struct inode *inode, + unsigned int len, const char *str, const struct qstr *name) { - return isofs_dentry_cmpi_common(dentry, a, b, 1); + return isofs_dentry_cmp_common(len, str, name, 1, 1); } #endif diff --git a/fs/isofs/namei.c b/fs/isofs/namei.c index 0d23abfd428..715f7d31804 100644 --- a/fs/isofs/namei.c +++ b/fs/isofs/namei.c @@ -37,7 +37,8 @@ isofs_cmp(struct dentry *dentry, const char *compare, int dlen) qstr.name = compare; qstr.len = dlen; - return dentry->d_op->d_compare(dentry, &dentry->d_name, &qstr); + return dentry->d_op->d_compare(NULL, NULL, NULL, NULL, + dentry->d_name.len, dentry->d_name.name, &qstr); } /* -- cgit v1.2.3-18-g5258 From b1e6a015a580ad145689ad1d6b4aa0e03e6c868b Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Fri, 7 Jan 2011 17:49:28 +1100 Subject: fs: change d_hash for rcu-walk Change d_hash so it may be called from lock-free RCU lookups. See similar patch for d_compare for details. For in-tree filesystems, this is just a mechanical change. Signed-off-by: Nick Piggin --- fs/isofs/inode.c | 28 ++++++++++++++++++---------- 1 file changed, 18 insertions(+), 10 deletions(-) (limited to 'fs/isofs') diff --git a/fs/isofs/inode.c b/fs/isofs/inode.c index 7b0fbc61af8..d204ee4235f 100644 --- a/fs/isofs/inode.c +++ b/fs/isofs/inode.c @@ -26,8 +26,10 @@ #define BEQUIET -static int isofs_hashi(struct dentry *parent, struct qstr *qstr); -static int isofs_hash(struct dentry *parent, struct qstr *qstr); +static int isofs_hashi(const struct dentry *parent, const struct inode *inode, + struct qstr *qstr); +static int isofs_hash(const struct dentry *parent, const struct inode *inode, + struct qstr *qstr); static int isofs_dentry_cmpi(const struct dentry *parent, const struct inode *pinode, const struct dentry *dentry, const struct inode *inode, @@ -38,8 +40,10 @@ static int isofs_dentry_cmp(const struct dentry *parent, unsigned int len, const char *str, const struct qstr *name); #ifdef CONFIG_JOLIET -static int isofs_hashi_ms(struct dentry *parent, struct qstr *qstr); -static int isofs_hash_ms(struct dentry *parent, struct qstr *qstr); +static int isofs_hashi_ms(const struct dentry *parent, const struct inode *inode, + struct qstr *qstr); +static int isofs_hash_ms(const struct dentry *parent, const struct inode *inode, + struct qstr *qstr); static int isofs_dentry_cmpi_ms(const struct dentry *parent, const struct inode *pinode, const struct dentry *dentry, const struct inode *inode, @@ -172,7 +176,7 @@ struct iso9660_options{ * Compute the hash for the isofs name corresponding to the dentry. */ static int -isofs_hash_common(struct dentry *dentry, struct qstr *qstr, int ms) +isofs_hash_common(const struct dentry *dentry, struct qstr *qstr, int ms) { const char *name; int len; @@ -193,7 +197,7 @@ isofs_hash_common(struct dentry *dentry, struct qstr *qstr, int ms) * Compute the hash for the isofs name corresponding to the dentry. */ static int -isofs_hashi_common(struct dentry *dentry, struct qstr *qstr, int ms) +isofs_hashi_common(const struct dentry *dentry, struct qstr *qstr, int ms) { const char *name; int len; @@ -248,13 +252,15 @@ static int isofs_dentry_cmp_common( } static int -isofs_hash(struct dentry *dentry, struct qstr *qstr) +isofs_hash(const struct dentry *dentry, const struct inode *inode, + struct qstr *qstr) { return isofs_hash_common(dentry, qstr, 0); } static int -isofs_hashi(struct dentry *dentry, struct qstr *qstr) +isofs_hashi(const struct dentry *dentry, const struct inode *inode, + struct qstr *qstr) { return isofs_hashi_common(dentry, qstr, 0); } @@ -277,13 +283,15 @@ isofs_dentry_cmpi(const struct dentry *parent, const struct inode *pinode, #ifdef CONFIG_JOLIET static int -isofs_hash_ms(struct dentry *dentry, struct qstr *qstr) +isofs_hash_ms(const struct dentry *dentry, const struct inode *inode, + struct qstr *qstr) { return isofs_hash_common(dentry, qstr, 1); } static int -isofs_hashi_ms(struct dentry *dentry, struct qstr *qstr) +isofs_hashi_ms(const struct dentry *dentry, const struct inode *inode, + struct qstr *qstr) { return isofs_hashi_common(dentry, qstr, 1); } -- cgit v1.2.3-18-g5258 From fa0d7e3de6d6fc5004ad9dea0dd6b286af8f03e9 Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Fri, 7 Jan 2011 17:49:49 +1100 Subject: fs: icache RCU free inodes RCU free the struct inode. This will allow: - Subsequent store-free path walking patch. The inode must be consulted for permissions when walking, so an RCU inode reference is a must. - sb_inode_list_lock to be moved inside i_lock because sb list walkers who want to take i_lock no longer need to take sb_inode_list_lock to walk the list in the first place. This will simplify and optimize locking. - Could remove some nested trylock loops in dcache code - Could potentially simplify things a bit in VM land. Do not need to take the page lock to follow page->mapping. The downsides of this is the performance cost of using RCU. In a simple creat/unlink microbenchmark, performance drops by about 10% due to inability to reuse cache-hot slab objects. As iterations increase and RCU freeing starts kicking over, this increases to about 20%. In cases where inode lifetimes are longer (ie. many inodes may be allocated during the average life span of a single inode), a lot of this cache reuse is not applicable, so the regression caused by this patch is smaller. The cache-hot regression could largely be avoided by using SLAB_DESTROY_BY_RCU, however this adds some complexity to list walking and store-free path walking, so I prefer to implement this at a later date, if it is shown to be a win in real situations. I haven't found a regression in any non-micro benchmark so I doubt it will be a problem. Signed-off-by: Nick Piggin --- fs/isofs/inode.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'fs/isofs') diff --git a/fs/isofs/inode.c b/fs/isofs/inode.c index d204ee4235f..d8f3a652243 100644 --- a/fs/isofs/inode.c +++ b/fs/isofs/inode.c @@ -81,11 +81,18 @@ static struct inode *isofs_alloc_inode(struct super_block *sb) return &ei->vfs_inode; } -static void isofs_destroy_inode(struct inode *inode) +static void isofs_i_callback(struct rcu_head *head) { + struct inode *inode = container_of(head, struct inode, i_rcu); + INIT_LIST_HEAD(&inode->i_dentry); kmem_cache_free(isofs_inode_cachep, ISOFS_I(inode)); } +static void isofs_destroy_inode(struct inode *inode) +{ + call_rcu(&inode->i_rcu, isofs_i_callback); +} + static void init_once(void *foo) { struct iso_inode_info *ei = foo; -- cgit v1.2.3-18-g5258 From fb045adb99d9b7c562dc7fef834857f78249daa1 Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Fri, 7 Jan 2011 17:49:55 +1100 Subject: fs: dcache reduce branches in lookup path Reduce some branches and memory accesses in dcache lookup by adding dentry flags to indicate common d_ops are set, rather than having to check them. This saves a pointer memory access (dentry->d_op) in common path lookup situations, and saves another pointer load and branch in cases where we have d_op but not the particular operation. Patched with: git grep -E '[.>]([[:space:]])*d_op([[:space:]])*=' | xargs sed -e 's/\([^\t ]*\)->d_op = \(.*\);/d_set_d_op(\1, \2);/' -e 's/\([^\t ]*\)\.d_op = \(.*\);/d_set_d_op(\&\1, \2);/' -i Signed-off-by: Nick Piggin --- fs/isofs/inode.c | 2 +- fs/isofs/namei.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) (limited to 'fs/isofs') diff --git a/fs/isofs/inode.c b/fs/isofs/inode.c index d8f3a652243..844a7903c72 100644 --- a/fs/isofs/inode.c +++ b/fs/isofs/inode.c @@ -949,7 +949,7 @@ root_found: table += 2; if (opt.check == 'r') table++; - s->s_root->d_op = &isofs_dentry_ops[table]; + d_set_d_op(s->s_root, &isofs_dentry_ops[table]); kfree(opt.iocharset); diff --git a/fs/isofs/namei.c b/fs/isofs/namei.c index 715f7d31804..679a849c3b2 100644 --- a/fs/isofs/namei.c +++ b/fs/isofs/namei.c @@ -172,7 +172,7 @@ struct dentry *isofs_lookup(struct inode *dir, struct dentry *dentry, struct nam struct inode *inode; struct page *page; - dentry->d_op = dir->i_sb->s_root->d_op; + d_set_d_op(dentry, dir->i_sb->s_root->d_op); page = alloc_page(GFP_USER); if (!page) -- cgit v1.2.3-18-g5258