Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755168AbXHVCuP (ORCPT ); Tue, 21 Aug 2007 22:50:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753278AbXHVCuD (ORCPT ); Tue, 21 Aug 2007 22:50:03 -0400 Received: from out2.smtp.messagingengine.com ([66.111.4.26]:46343 "EHLO out2.smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753209AbXHVCuA (ORCPT ); Tue, 21 Aug 2007 22:50:00 -0400 X-Sasl-enc: hdJYpGvTgySqOaxWWc3qY4FBvUla3+m8aw2Mi86+x/cW 1187750998 Subject: Re: [PATCH] autofs4: reinstate negatitive timeout of mount fails From: Ian Kent To: Peter Staubach Cc: Andrew Morton , Kernel Mailing List , autofs mailing list In-Reply-To: <46CAF484.80501@redhat.com> References: <1187688369.3318.12.camel@raven.themaw.net> <46CAF484.80501@redhat.com> Content-Type: text/plain Date: Wed, 22 Aug 2007 10:49:52 +0800 Message-Id: <1187750992.3899.3.camel@raven.themaw.net> Mime-Version: 1.0 X-Mailer: Evolution 2.10.3 (2.10.3-2.fc7) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 16243 Lines: 478 On Tue, 2007-08-21 at 10:19 -0400, Peter Staubach wrote: > Ian Kent wrote: > > Hi, > > > > Due to a change to fs/dcache.c:d_lookup() in the 2.6 kernel whereby only > > hashed dentrys are returned the negative caching of mount failures > > stopped working in the autofs4 module for nobrowse mount (ie. directory > > created at mount time and removed at umount or following a mount > > failure). > > > > This patch keeps track of the dentrys from mount fails in order to be > > able check the timeout since the last fail and return the appropriate > > status. In addition the timeout value is settable at load time as a > > module option and via sysfs using the module > > parameter /sys/module/autofs4/parameters/negative_timeout. > > > > Signed-off-by: Ian Kent > > > > --- > > --- linux-2.6.23-rc2-mm2/fs/autofs4/init.c.negative-timeout 2007-07-09 07:32:17.000000000 +0800 > > +++ linux-2.6.23-rc2-mm2/fs/autofs4/init.c 2007-08-21 15:44:34.000000000 +0800 > > @@ -14,6 +14,10 @@ > > #include > > #include "autofs_i.h" > > > > +unsigned int negative_timeout = AUTOFS_NEGATIVE_TIMEOUT; > > +module_param(negative_timeout, uint, S_IRUGO | S_IWUSR); > > +MODULE_PARM_DESC(negative_timeout, "Cache mount fails negatively for this many seconds"); > > + > > static int autofs_get_sb(struct file_system_type *fs_type, > > int flags, const char *dev_name, void *data, struct vfsmount *mnt) > > { > > --- linux-2.6.23-rc2-mm2/fs/autofs4/inode.c.negative-timeout 2007-08-17 11:52:33.000000000 +0800 > > +++ linux-2.6.23-rc2-mm2/fs/autofs4/inode.c 2007-08-21 15:44:34.000000000 +0800 > > @@ -46,6 +46,7 @@ struct autofs_info *autofs4_init_ino(str > > ino->inode = NULL; > > ino->dentry = NULL; > > ino->size = 0; > > + ino->negative_timeout = negative_timeout; > > > > INIT_LIST_HEAD(&ino->rehash); > > > > @@ -98,11 +99,24 @@ void autofs4_free_ino(struct autofs_info > > static void autofs4_force_release(struct autofs_sb_info *sbi) > > { > > struct dentry *this_parent = sbi->sb->s_root; > > - struct list_head *next; > > + struct list_head *p, *next; > > > > if (!sbi->sb->s_root) > > return; > > > > + /* Cleanup the negative dentry cache */ > > + spin_lock(&sbi->rehash_lock); > > + list_for_each_safe(p, next, &sbi->rehash_list) { > > + struct autofs_info *ino; > > + struct dentry *dentry; > > + ino = list_entry(p, struct autofs_info, rehash); > > + dentry = ino->dentry; > > + spin_unlock(&sbi->rehash_lock); > > + dput(ino->dentry); > > > > Should this be dput(dentry);? It could be since they're the same or maybe I should get rid of the assignment. Maybe that would save a couple of cpu cycles. > > Thanx... > > ps > > > > + spin_lock(&sbi->rehash_lock); > > + } > > + spin_unlock(&sbi->rehash_lock); > > + > > spin_lock(&dcache_lock); > > repeat: > > next = this_parent->d_subdirs.next; > > --- linux-2.6.23-rc2-mm2/fs/autofs4/autofs_i.h.negative-timeout 2007-08-17 11:52:33.000000000 +0800 > > +++ linux-2.6.23-rc2-mm2/fs/autofs4/autofs_i.h 2007-08-21 15:44:34.000000000 +0800 > > @@ -40,6 +40,14 @@ > > #define DPRINTK(fmt,args...) do {} while(0) > > #endif > > > > +/* > > + * If the daemon returns a negative response (AUTOFS_IOC_FAIL) then we keep > > + * the negative response cached for up to the time given here, although > > + * the time can be shorter if the kernel throws the dcache entry away. > > + */ > > +#define AUTOFS_NEGATIVE_TIMEOUT 60 /* default 1 minute */ > > +extern unsigned int negative_timeout; > > + > > /* Unified info structure. This is pointed to by both the dentry and > > inode structures. Each file in the filesystem has an instance of this > > structure. It holds a reference to the dentry, so dentries are never > > @@ -52,8 +60,16 @@ struct autofs_info { > > > > int flags; > > > > + /* > > + * Two types of unhashed dentry can exist on this list. > > + * Negative dentrys from failed mounts and positive dentrys > > + * resulting from a race between expire and mount. This > > + * fact is used when looking for dentrys in the list. > > + */ > > struct list_head rehash; > > > > + unsigned int negative_timeout; > > + > > struct autofs_sb_info *sbi; > > unsigned long last_used; > > atomic_t count; > > --- linux-2.6.23-rc2-mm2/fs/autofs4/root.c.negative-timeout 2007-08-17 11:53:38.000000000 +0800 > > +++ linux-2.6.23-rc2-mm2/fs/autofs4/root.c 2007-08-21 15:44:34.000000000 +0800 > > @@ -238,6 +238,125 @@ out: > > return dcache_readdir(file, dirent, filldir); > > } > > > > +static int autofs4_compare_dentry(struct dentry *parent, struct dentry *dentry, struct qstr *name) > > +{ > > + unsigned int len = name->len; > > + unsigned int hash = name->hash; > > + const unsigned char *str = name->name; > > + struct qstr *qstr = &dentry->d_name; > > + > > + if (dentry->d_name.hash != hash) > > + return 0; > > + if (dentry->d_parent != parent) > > + return 0; > > + > > + if (qstr->len != len) > > + return 0; > > + if (memcmp(qstr->name, str, len)) > > + return 0; > > + > > + return 1; > > +} > > + > > +static struct dentry *autofs4_lookup_dentry(struct autofs_sb_info *sbi, struct dentry *dentry) > > +{ > > + struct dentry *parent = dentry->d_parent; > > + struct qstr *name = &dentry->d_name; > > + struct list_head *p, *head; > > + > > + head = &sbi->rehash_list; > > + list_for_each(p, head) { > > + struct autofs_info *ino; > > + struct dentry *this; > > + > > + ino = list_entry(p, struct autofs_info, rehash); > > + this = ino->dentry; > > + > > + spin_lock(&this->d_lock); > > + > > + if (!autofs4_compare_dentry(parent, this, name)) > > + goto next; > > + > > + if (d_unhashed(this)) { > > + spin_unlock(&this->d_lock); > > + return this; > > + } > > +next: > > + spin_unlock(&this->d_lock); > > + } > > + > > + return NULL; > > +} > > + > > +static struct dentry *autofs4_lookup_negative(struct autofs_sb_info *sbi, struct dentry *dentry) > > +{ > > + struct dentry *parent = dentry->d_parent; > > + struct qstr *name = &dentry->d_name; > > + struct list_head *p, *head; > > + > > + spin_lock(&sbi->rehash_lock); > > + head = &sbi->rehash_list; > > + list_for_each(p, head) { > > + struct autofs_info *ino; > > + struct dentry *this; > > + > > + ino = list_entry(p, struct autofs_info, rehash); > > + this = ino->dentry; > > + > > + spin_lock(&this->d_lock); > > + > > + if (this->d_inode) > > + goto next; > > + > > + if (!autofs4_compare_dentry(parent, this, name)) > > + goto next; > > + > > + if (d_unhashed(this)) { > > + if (autofs4_oz_mode(sbi)) { > > + spin_unlock(&this->d_lock); > > + spin_unlock(&sbi->rehash_lock); > > + return this; > > + } > > + /* > > + * If d_time is non-zero we've had a mount fail. > > + * Check if it's time to forget about it, return > > + * fail if not. > > + */ > > + if (this->d_time) { > > + struct autofs_info *p_ino; > > + unsigned long neg_timeout; > > + > > + neg_timeout = this->d_time - get_seconds(); > > + if (neg_timeout <= ino->negative_timeout) { > > + spin_unlock(&this->d_lock); > > + spin_unlock(&sbi->rehash_lock); > > + return ERR_PTR(-ENOENT); > > + } > > + /* Negative cache timeout */ > > + this->d_time = 0; > > + list_del_init(&ino->rehash); > > + spin_unlock(&this->d_lock); > > + spin_unlock(&sbi->rehash_lock); > > + if (atomic_dec_and_test(&ino->count)) { > > + p_ino = autofs4_dentry_ino(this->d_parent); > > + if (p_ino && this->d_parent != this) > > + atomic_dec(&p_ino->count); > > + } > > + dput(this); > > + return NULL; > > + } > > + spin_unlock(&this->d_lock); > > + spin_unlock(&sbi->rehash_lock); > > + return this; > > + } > > +next: > > + spin_unlock(&this->d_lock); > > + } > > + spin_unlock(&sbi->rehash_lock); > > + > > + return NULL; > > +} > > + > > static int try_to_fill_dentry(struct dentry *dentry, int flags) > > { > > struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb); > > @@ -282,7 +401,27 @@ static int try_to_fill_dentry(struct den > > > > /* Turn this into a real negative dentry? */ > > if (status == -ENOENT) { > > + if (!ino) { > > + ino = autofs4_init_ino(ino, sbi, S_IFDIR | 0555); > > + if (ino == NULL) > > + return -ENOSPC; > > + dentry->d_fsdata = ino; > > + } > > + spin_lock(&sbi->rehash_lock); > > + if (!autofs4_lookup_dentry(sbi, dentry)) { > > + struct autofs_info *p_ino; > > + ino->dentry = dget(dentry); > > + atomic_inc(&ino->count); > > + p_ino = autofs4_dentry_ino(dentry->d_parent); > > + if (p_ino && dentry->d_parent != dentry) > > + atomic_inc(&p_ino->count); > > + list_add(&ino->rehash, &sbi->rehash_list); > > + } > > + spin_unlock(&sbi->rehash_lock); > > + /* Set time at which we forget about this mount fial */ > > spin_lock(&dentry->d_lock); > > + ino->negative_timeout = negative_timeout; > > + dentry->d_time = get_seconds() + negative_timeout; > > dentry->d_flags &= ~DCACHE_AUTOFS_PENDING; > > spin_unlock(&dentry->d_lock); > > return status; > > @@ -305,6 +444,11 @@ static int try_to_fill_dentry(struct den > > > > if (status) { > > spin_lock(&dentry->d_lock); > > + /* Set time at which we forget about this mount fial */ > > + if (status == -ENOENT) { > > + ino->negative_timeout = negative_timeout; > > + dentry->d_time = get_seconds() + negative_timeout; > > + } > > dentry->d_flags &= ~DCACHE_AUTOFS_PENDING; > > spin_unlock(&dentry->d_lock); > > return status; > > @@ -316,6 +460,7 @@ static int try_to_fill_dentry(struct den > > ino->last_used = jiffies; > > > > spin_lock(&dentry->d_lock); > > + dentry->d_time = 0; > > dentry->d_flags &= ~DCACHE_AUTOFS_PENDING; > > spin_unlock(&dentry->d_lock); > > return status; > > @@ -339,6 +484,19 @@ static void *autofs4_follow_link(struct > > if (oz_mode || !lookup_type) > > goto done; > > > > + /* Check for cached mount fail, reset d_time if timed out */ > > + spin_lock(&dentry->d_lock); > > + if (dentry->d_time) { > > + unsigned long neg_timeout = dentry->d_time - get_seconds(); > > + if (neg_timeout <= ino->negative_timeout) { > > + spin_unlock(&dentry->d_lock); > > + status = -ENOENT; > > + goto out_error; > > + } > > + dentry->d_time = 0; > > + } > > + spin_unlock(&dentry->d_lock); > > + > > /* If an expire request is pending wait for it. */ > > if (ino && (ino->flags & AUTOFS_INF_EXPIRING)) { > > DPRINTK("waiting for active request %p name=%.*s", > > @@ -426,9 +584,28 @@ static int autofs4_revalidate(struct den > > return status; > > } > > > > - /* Negative dentry.. invalidate if "old" */ > > - if (dentry->d_inode == NULL) > > - return 0; > > + /* Check for cached mount fail, reset d_time if timed out */ > > + spin_lock(&dentry->d_lock); > > + if (!dentry->d_inode || dentry->d_time) { > > + struct autofs_info *ino = autofs4_dentry_ino(dentry); > > + unsigned long neg_timeout = dentry->d_time - get_seconds(); > > + /* > > + * If d_time is non-zero we've had a mount fail. Check if > > + * it's time to forget about it, return fail if not. > > + */ > > + if (dentry->d_time && (neg_timeout <= ino->negative_timeout)) { > > + spin_unlock(&dentry->d_lock); > > + return 1; > > + } > > + /* Negative timeout has expired */ > > + dentry->d_time = 0; > > + > > + if (!dentry->d_inode) { > > + spin_unlock(&dentry->d_lock); > > + return 0; > > + } > > + } > > + spin_unlock(&dentry->d_lock); > > > > /* Check for a non-mountpoint directory with no contents */ > > spin_lock(&dcache_lock); > > @@ -497,9 +674,6 @@ static struct dentry_operations autofs4_ > > > > static struct dentry *autofs4_lookup_unhashed(struct autofs_sb_info *sbi, struct dentry *parent, struct qstr *name) > > { > > - unsigned int len = name->len; > > - unsigned int hash = name->hash; > > - const unsigned char *str = name->name; > > struct list_head *p, *head; > > > > spin_lock(&dcache_lock); > > @@ -508,7 +682,6 @@ static struct dentry *autofs4_lookup_unh > > list_for_each(p, head) { > > struct autofs_info *ino; > > struct dentry *dentry; > > - struct qstr *qstr; > > > > ino = list_entry(p, struct autofs_info, rehash); > > dentry = ino->dentry; > > @@ -519,20 +692,10 @@ static struct dentry *autofs4_lookup_unh > > if (!dentry->d_inode) > > goto next; > > > > - qstr = &dentry->d_name; > > - > > - if (dentry->d_name.hash != hash) > > - goto next; > > - if (dentry->d_parent != parent) > > - goto next; > > - > > - if (qstr->len != len) > > - goto next; > > - if (memcmp(qstr->name, str, len)) > > + if (!autofs4_compare_dentry(parent, dentry, name)) > > goto next; > > > > if (d_unhashed(dentry)) { > > - struct autofs_info *ino = autofs4_dentry_ino(dentry); > > struct inode *inode = dentry->d_inode; > > > > list_del_init(&ino->rehash); > > @@ -568,7 +731,7 @@ next: > > static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd) > > { > > struct autofs_sb_info *sbi; > > - struct dentry *unhashed; > > + struct dentry *unhashed, *negative = NULL; > > int oz_mode; > > > > DPRINTK("name = %.*s", > > @@ -587,6 +750,22 @@ static struct dentry *autofs4_lookup(str > > unhashed = autofs4_lookup_unhashed(sbi, dentry->d_parent, &dentry->d_name); > > if (!unhashed) { > > /* > > + * Negative caching of failed "nobrowse" autofs mounts > > + * require that we keep the unhashed, negative dentrys > > + * around so we can use them to check failure status. We > > + * use the rehash_list list in the super bloxk for this > > + * purpose. This isn't needed for "browse" or direct mounts > > + * as the dentrys are always positive so the info is always > > + * available. > > + */ > > + negative = autofs4_lookup_negative(sbi, dentry); > > + if (negative) { > > + if (IS_ERR(negative)) > > + return negative; > > + dentry = negative; > > + goto found; > > + } > > + /* > > * Mark the dentry incomplete but don't hash it. We do this > > * to serialize our inode creation operations (symlink and > > * mkdir) which prevents deadlock during the callback to > > @@ -599,6 +778,7 @@ static struct dentry *autofs4_lookup(str > > */ > > dentry->d_op = &autofs4_root_dentry_operations; > > > > + dentry->d_time = 0; > > dentry->d_fsdata = NULL; > > d_instantiate(dentry, NULL); > > } else { > > @@ -621,7 +801,7 @@ static struct dentry *autofs4_lookup(str > > } > > dentry = unhashed; > > } > > - > > +found: > > if (!oz_mode) { > > spin_lock(&dentry->d_lock); > > dentry->d_flags |= DCACHE_AUTOFS_PENDING; > > @@ -682,7 +862,7 @@ static struct dentry *autofs4_lookup(str > > return dentry; > > } > > > > - if (unhashed) > > + if (unhashed || negative) > > return dentry; > > > > return NULL; > > @@ -779,7 +959,9 @@ static int autofs4_dir_unlink(struct ino > > > > spin_lock(&dcache_lock); > > spin_lock(&sbi->rehash_lock); > > - list_add(&ino->rehash, &sbi->rehash_list); > > + dentry->d_time = 0; > > + if (!autofs4_lookup_dentry(sbi, dentry)) > > + list_add(&ino->rehash, &sbi->rehash_list); > > spin_unlock(&sbi->rehash_lock); > > spin_lock(&dentry->d_lock); > > __d_drop(dentry); > > @@ -807,7 +989,9 @@ static int autofs4_dir_rmdir(struct inod > > return -ENOTEMPTY; > > } > > spin_lock(&sbi->rehash_lock); > > - list_add(&ino->rehash, &sbi->rehash_list); > > + dentry->d_time = 0; > > + if (!autofs4_lookup_dentry(sbi, dentry)) > > + list_add(&ino->rehash, &sbi->rehash_list); > > spin_unlock(&sbi->rehash_lock); > > spin_lock(&dentry->d_lock); > > __d_drop(dentry); > > > > > > - > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > Please read the FAQ at http://www.tux.org/lkml/ > > > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/