From 213614d583748d00967a91cacd656f417efb36ce Mon Sep 17 00:00:00 2001 From: Ian Kent Date: Tue, 15 Dec 2009 16:45:51 -0800 Subject: autofs4: always use lookup for lookup We need to be able to cope with the directory mutex being held during ->d_revalidate() in some cases, but not all cases, and not necessarily by us. Because we need to release the mutex when we call back to the daemon to do perform a mount we must be sure that it is us who holds the mutex so we must redirect mount requests to ->lookup() if the mutex is held. Signed-off-by: Ian Kent Cc: Sage Weil Cc: Al Viro Cc: Andreas Dilger Cc: Christoph Hellwig Cc: Yehuda Saheh Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/autofs4/root.c | 474 ++++++++++++++++++++++++++++++++++++------------------ 1 file changed, 317 insertions(+), 157 deletions(-) (limited to 'fs/autofs4/root.c') diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c index a015b49891df..30cc9ddf4b70 100644 --- a/fs/autofs4/root.c +++ b/fs/autofs4/root.c @@ -104,6 +104,99 @@ static void autofs4_del_active(struct dentry *dentry) return; } +static void autofs4_add_rehash_entry(struct autofs_info *ino, + struct rehash_entry *entry) +{ + entry->task = current; + INIT_LIST_HEAD(&entry->list); + list_add(&entry->list, &ino->rehash_list); + return; +} + +static void autofs4_remove_rehash_entry(struct autofs_info *ino) +{ + struct list_head *head = &ino->rehash_list; + struct rehash_entry *entry; + list_for_each_entry(entry, head, list) { + if (entry->task == current) { + list_del(&entry->list); + kfree(entry); + break; + } + } + return; +} + +static void autofs4_remove_rehash_entrys(struct autofs_info *ino) +{ + struct autofs_sb_info *sbi = ino->sbi; + struct rehash_entry *entry, *next; + struct list_head *head; + + spin_lock(&sbi->fs_lock); + spin_lock(&sbi->lookup_lock); + if (!(ino->flags & AUTOFS_INF_REHASH)) { + spin_unlock(&sbi->lookup_lock); + spin_unlock(&sbi->fs_lock); + return; + } + ino->flags &= ~AUTOFS_INF_REHASH; + head = &ino->rehash_list; + list_for_each_entry_safe(entry, next, head, list) { + list_del(&entry->list); + kfree(entry); + } + spin_unlock(&sbi->lookup_lock); + spin_unlock(&sbi->fs_lock); + dput(ino->dentry); + + return; +} + +static void autofs4_revalidate_drop(struct dentry *dentry, + struct rehash_entry *entry) +{ + struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb); + struct autofs_info *ino = autofs4_dentry_ino(dentry); + /* + * Add to the active list so we can pick this up in + * ->lookup(). Also add an entry to a rehash list so + * we know when there are no dentrys in flight so we + * know when we can rehash the dentry. + */ + spin_lock(&sbi->lookup_lock); + if (list_empty(&ino->active)) + list_add(&ino->active, &sbi->active_list); + autofs4_add_rehash_entry(ino, entry); + spin_unlock(&sbi->lookup_lock); + if (!(ino->flags & AUTOFS_INF_REHASH)) { + ino->flags |= AUTOFS_INF_REHASH; + dget(dentry); + spin_lock(&dentry->d_lock); + __d_drop(dentry); + spin_unlock(&dentry->d_lock); + } + return; +} + +static void autofs4_revalidate_rehash(struct dentry *dentry) +{ + struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb); + struct autofs_info *ino = autofs4_dentry_ino(dentry); + if (ino->flags & AUTOFS_INF_REHASH) { + spin_lock(&sbi->lookup_lock); + autofs4_remove_rehash_entry(ino); + if (list_empty(&ino->rehash_list)) { + spin_unlock(&sbi->lookup_lock); + ino->flags &= ~AUTOFS_INF_REHASH; + d_rehash(dentry); + dput(ino->dentry); + } else + spin_unlock(&sbi->lookup_lock); + } + return; +} + static unsigned int autofs4_need_mount(unsigned int flags) { unsigned int res = 0; @@ -143,7 +236,7 @@ out: return dcache_dir_open(inode, file); } -static int try_to_fill_dentry(struct dentry *dentry, int flags) +static int try_to_fill_dentry(struct dentry *dentry) { struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb); struct autofs_info *ino = autofs4_dentry_ino(dentry); @@ -156,55 +249,17 @@ static int try_to_fill_dentry(struct dentry *dentry, int flags) * Wait for a pending mount, triggering one if there * isn't one already */ - if (dentry->d_inode == NULL) { - DPRINTK("waiting for mount name=%.*s", - dentry->d_name.len, dentry->d_name.name); + DPRINTK("waiting for mount name=%.*s", + dentry->d_name.len, dentry->d_name.name); - status = autofs4_wait(sbi, dentry, NFY_MOUNT); + status = autofs4_wait(sbi, dentry, NFY_MOUNT); - DPRINTK("mount done status=%d", status); - - /* Turn this into a real negative dentry? */ - if (status == -ENOENT) { - spin_lock(&sbi->fs_lock); - ino->flags &= ~AUTOFS_INF_PENDING; - spin_unlock(&sbi->fs_lock); - return status; - } else if (status) { - /* Return a negative dentry, but leave it "pending" */ - return status; - } - /* Trigger mount for path component or follow link */ - } else if (ino->flags & AUTOFS_INF_PENDING || - autofs4_need_mount(flags) || - current->link_count) { - DPRINTK("waiting for mount name=%.*s", - dentry->d_name.len, dentry->d_name.name); + DPRINTK("mount done status=%d", status); - spin_lock(&sbi->fs_lock); - ino->flags |= AUTOFS_INF_PENDING; - spin_unlock(&sbi->fs_lock); - status = autofs4_wait(sbi, dentry, NFY_MOUNT); + /* Update expiry counter */ + ino->last_used = jiffies; - DPRINTK("mount done status=%d", status); - - if (status) { - spin_lock(&sbi->fs_lock); - ino->flags &= ~AUTOFS_INF_PENDING; - spin_unlock(&sbi->fs_lock); - return status; - } - } - - /* Initialize expiry counter after successful mount */ - if (ino) - ino->last_used = jiffies; - - spin_lock(&sbi->fs_lock); - ino->flags &= ~AUTOFS_INF_PENDING; - spin_unlock(&sbi->fs_lock); - - return 0; + return status; } /* For autofs direct mounts the follow link triggers the mount */ @@ -258,10 +313,16 @@ static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd) */ if (ino->flags & AUTOFS_INF_PENDING || (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs))) { + ino->flags |= AUTOFS_INF_PENDING; spin_unlock(&dcache_lock); spin_unlock(&sbi->fs_lock); - status = try_to_fill_dentry(dentry, 0); + status = try_to_fill_dentry(dentry); + + spin_lock(&sbi->fs_lock); + ino->flags &= ~AUTOFS_INF_PENDING; + spin_unlock(&sbi->fs_lock); + if (status) goto out_error; @@ -300,18 +361,47 @@ static int autofs4_revalidate(struct dentry *dentry, struct nameidata *nd) { struct inode *dir = dentry->d_parent->d_inode; struct autofs_sb_info *sbi = autofs4_sbi(dir->i_sb); - int oz_mode = autofs4_oz_mode(sbi); + struct autofs_info *ino = autofs4_dentry_ino(dentry); + struct rehash_entry *entry; int flags = nd ? nd->flags : 0; - int status = 1; + unsigned int mutex_aquired; + + DPRINTK("name = %.*s oz_mode = %d", + dentry->d_name.len, dentry->d_name.name, oz_mode); + + /* Daemon never causes a mount to trigger */ + if (autofs4_oz_mode(sbi)) + return 1; + + entry = kmalloc(sizeof(struct rehash_entry), GFP_KERNEL); + if (!entry) + return -ENOMEM; + + mutex_aquired = mutex_trylock(&dir->i_mutex); - /* Pending dentry */ spin_lock(&sbi->fs_lock); + spin_lock(&dcache_lock); + /* Pending dentry */ if (autofs4_ispending(dentry)) { - /* The daemon never causes a mount to trigger */ - spin_unlock(&sbi->fs_lock); + int status; - if (oz_mode) - return 1; + /* + * We can only unhash and send this to ->lookup() if + * the directory mutex is held over d_revalidate() and + * ->lookup(). This prevents the VFS from incorrectly + * seeing the dentry as non-existent. + */ + ino->flags |= AUTOFS_INF_PENDING; + if (!mutex_aquired) { + autofs4_revalidate_drop(dentry, entry); + spin_unlock(&dcache_lock); + spin_unlock(&sbi->fs_lock); + return 0; + } + spin_unlock(&dcache_lock); + spin_unlock(&sbi->fs_lock); + mutex_unlock(&dir->i_mutex); + kfree(entry); /* * If the directory has gone away due to an expire @@ -325,45 +415,82 @@ static int autofs4_revalidate(struct dentry *dentry, struct nameidata *nd) * A zero status is success otherwise we have a * negative error code. */ - status = try_to_fill_dentry(dentry, flags); + status = try_to_fill_dentry(dentry); + + spin_lock(&sbi->fs_lock); + ino->flags &= ~AUTOFS_INF_PENDING; + spin_unlock(&sbi->fs_lock); + if (status == 0) return 1; return status; } - spin_unlock(&sbi->fs_lock); - - /* Negative dentry.. invalidate if "old" */ - if (dentry->d_inode == NULL) - return 0; /* Check for a non-mountpoint directory with no contents */ - spin_lock(&dcache_lock); if (S_ISDIR(dentry->d_inode->i_mode) && !d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) { DPRINTK("dentry=%p %.*s, emptydir", dentry, dentry->d_name.len, dentry->d_name.name); - spin_unlock(&dcache_lock); - /* The daemon never causes a mount to trigger */ - if (oz_mode) - return 1; + if (autofs4_need_mount(flags) || current->link_count) { + int status; - /* - * A zero status is success otherwise we have a - * negative error code. - */ - status = try_to_fill_dentry(dentry, flags); - if (status == 0) - return 1; + /* + * We can only unhash and send this to ->lookup() if + * the directory mutex is held over d_revalidate() and + * ->lookup(). This prevents the VFS from incorrectly + * seeing the dentry as non-existent. + */ + ino->flags |= AUTOFS_INF_PENDING; + if (!mutex_aquired) { + autofs4_revalidate_drop(dentry, entry); + spin_unlock(&dcache_lock); + spin_unlock(&sbi->fs_lock); + return 0; + } + spin_unlock(&dcache_lock); + spin_unlock(&sbi->fs_lock); + mutex_unlock(&dir->i_mutex); + kfree(entry); - return status; + /* + * A zero status is success otherwise we have a + * negative error code. + */ + status = try_to_fill_dentry(dentry); + + spin_lock(&sbi->fs_lock); + ino->flags &= ~AUTOFS_INF_PENDING; + spin_unlock(&sbi->fs_lock); + + if (status == 0) + return 1; + + return status; + } } spin_unlock(&dcache_lock); + spin_unlock(&sbi->fs_lock); + + if (mutex_aquired) + mutex_unlock(&dir->i_mutex); + + kfree(entry); return 1; } +static void autofs4_free_rehash_entrys(struct autofs_info *inf) +{ + struct list_head *head = &inf->rehash_list; + struct rehash_entry *entry, *next; + list_for_each_entry_safe(entry, next, head, list) { + list_del(&entry->list); + kfree(entry); + } +} + void autofs4_dentry_release(struct dentry *de) { struct autofs_info *inf; @@ -382,6 +509,8 @@ void autofs4_dentry_release(struct dentry *de) list_del(&inf->active); if (!list_empty(&inf->expiring)) list_del(&inf->expiring); + if (!list_empty(&inf->rehash_list)) + autofs4_free_rehash_entrys(inf); spin_unlock(&sbi->lookup_lock); } @@ -414,6 +543,7 @@ static struct dentry *autofs4_lookup_active(struct dentry *dentry) const unsigned char *str = name->name; struct list_head *p, *head; +restart: spin_lock(&dcache_lock); spin_lock(&sbi->lookup_lock); head = &sbi->active_list; @@ -431,6 +561,19 @@ static struct dentry *autofs4_lookup_active(struct dentry *dentry) if (atomic_read(&active->d_count) == 0) goto next; + if (active->d_inode && IS_DEADDIR(active->d_inode)) { + if (!list_empty(&ino->rehash_list)) { + dget(active); + spin_unlock(&active->d_lock); + spin_unlock(&sbi->lookup_lock); + spin_unlock(&dcache_lock); + autofs4_remove_rehash_entrys(ino); + dput(active); + goto restart; + } + goto next; + } + qstr = &active->d_name; if (active->d_name.hash != hash) @@ -443,13 +586,11 @@ static struct dentry *autofs4_lookup_active(struct dentry *dentry) if (memcmp(qstr->name, str, len)) goto next; - if (d_unhashed(active)) { - dget(active); - spin_unlock(&active->d_lock); - spin_unlock(&sbi->lookup_lock); - spin_unlock(&dcache_lock); - return active; - } + dget(active); + spin_unlock(&active->d_lock); + spin_unlock(&sbi->lookup_lock); + spin_unlock(&dcache_lock); + return active; next: spin_unlock(&active->d_lock); } @@ -498,13 +639,11 @@ static struct dentry *autofs4_lookup_expiring(struct dentry *dentry) if (memcmp(qstr->name, str, len)) goto next; - if (d_unhashed(expiring)) { - dget(expiring); - spin_unlock(&expiring->d_lock); - spin_unlock(&sbi->lookup_lock); - spin_unlock(&dcache_lock); - return expiring; - } + dget(expiring); + spin_unlock(&expiring->d_lock); + spin_unlock(&sbi->lookup_lock); + spin_unlock(&dcache_lock); + return expiring; next: spin_unlock(&expiring->d_lock); } @@ -514,6 +653,48 @@ next: return NULL; } +static struct autofs_info *init_new_dentry(struct autofs_sb_info *sbi, + struct dentry *dentry, int oz_mode) +{ + struct autofs_info *ino; + + /* + * 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 + * the daemon. Subsequent user space lookups for the same + * dentry are placed on the wait queue while the daemon + * itself is allowed passage unresticted so the create + * operation itself can then hash the dentry. Finally, + * we check for the hashed dentry and return the newly + * hashed dentry. + */ + dentry->d_op = &autofs4_root_dentry_operations; + + /* + * And we need to ensure that the same dentry is used for + * all following lookup calls until it is hashed so that + * the dentry flags are persistent throughout the request. + */ + ino = autofs4_init_ino(NULL, sbi, 0555); + if (!ino) + return ERR_PTR(-ENOMEM); + + dentry->d_fsdata = ino; + ino->dentry = dentry; + + /* + * Only set the mount pending flag for new dentrys not created + * by the daemon. + */ + if (!oz_mode) + ino->flags |= AUTOFS_INF_PENDING; + + d_instantiate(dentry, NULL); + + return ino; +} + /* Lookups in the root directory */ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, struct nameidata *nd) { @@ -521,6 +702,7 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s struct autofs_info *ino; struct dentry *expiring, *active; int oz_mode; + int status = 0; DPRINTK("name = %.*s", dentry->d_name.len, dentry->d_name.name); @@ -535,44 +717,26 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s DPRINTK("pid = %u, pgrp = %u, catatonic = %d, oz_mode = %d", current->pid, task_pgrp_nr(current), sbi->catatonic, oz_mode); + spin_lock(&sbi->fs_lock); active = autofs4_lookup_active(dentry); if (active) { dentry = active; ino = autofs4_dentry_ino(dentry); + /* If this came from revalidate, rehash it */ + autofs4_revalidate_rehash(dentry); + spin_unlock(&sbi->fs_lock); } else { - /* - * 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 - * the daemon. Subsequent user space lookups for the same - * dentry are placed on the wait queue while the daemon - * itself is allowed passage unresticted so the create - * operation itself can then hash the dentry. Finally, - * we check for the hashed dentry and return the newly - * hashed dentry. - */ - dentry->d_op = &autofs4_root_dentry_operations; - - /* - * And we need to ensure that the same dentry is used for - * all following lookup calls until it is hashed so that - * the dentry flags are persistent throughout the request. - */ - ino = autofs4_init_ino(NULL, sbi, 0555); - if (!ino) - return ERR_PTR(-ENOMEM); - - dentry->d_fsdata = ino; - ino->dentry = dentry; - - autofs4_add_active(dentry); - - d_instantiate(dentry, NULL); + spin_unlock(&sbi->fs_lock); + ino = init_new_dentry(sbi, dentry, oz_mode); + if (IS_ERR(ino)) + return (struct dentry *) ino; } + autofs4_add_active(dentry); + if (!oz_mode) { - mutex_unlock(&dir->i_mutex); expiring = autofs4_lookup_expiring(dentry); + mutex_unlock(&dir->i_mutex); if (expiring) { /* * If we are racing with expire the request might not @@ -580,23 +744,22 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s * so it must have been successful, so just wait for it. */ autofs4_expire_wait(expiring); - autofs4_del_expiring(expiring); dput(expiring); } - + status = try_to_fill_dentry(dentry); + mutex_lock(&dir->i_mutex); spin_lock(&sbi->fs_lock); - ino->flags |= AUTOFS_INF_PENDING; + ino->flags &= ~AUTOFS_INF_PENDING; spin_unlock(&sbi->fs_lock); - if (dentry->d_op && dentry->d_op->d_revalidate) - (dentry->d_op->d_revalidate)(dentry, nd); - mutex_lock(&dir->i_mutex); } + autofs4_del_active(dentry); + /* - * If we are still pending, check if we had to handle + * If we had a mount fail, check if we had to handle * a signal. If so we can force a restart.. */ - if (ino->flags & AUTOFS_INF_PENDING) { + if (status) { /* See if we were interrupted */ if (signal_pending(current)) { sigset_t *sigset = ¤t->pending.signal; @@ -608,43 +771,46 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s return ERR_PTR(-ERESTARTNOINTR); } } - if (!oz_mode) { - spin_lock(&sbi->fs_lock); - ino->flags &= ~AUTOFS_INF_PENDING; - spin_unlock(&sbi->fs_lock); - } } /* - * If this dentry is unhashed, then we shouldn't honour this - * lookup. Returning ENOENT here doesn't do the right thing - * for all system calls, but it should be OK for the operations - * we permit from an autofs. + * User space can (and has done in the past) remove and re-create + * this directory during the callback. This can leave us with an + * unhashed dentry, but a successful mount! So we need to + * perform another cached lookup in case the dentry now exists. */ - if (!oz_mode && d_unhashed(dentry)) { - /* - * A user space application can (and has done in the past) - * remove and re-create this directory during the callback. - * This can leave us with an unhashed dentry, but a - * successful mount! So we need to perform another - * cached lookup in case the dentry now exists. - */ - struct dentry *parent = dentry->d_parent; - struct dentry *new = d_lookup(parent, &dentry->d_name); - if (new != NULL) - dentry = new; - else - dentry = ERR_PTR(-ENOENT); + if (!oz_mode && !have_submounts(dentry)) { + struct dentry *new; + new = d_lookup(dentry->d_parent, &dentry->d_name); + if (new) { + if (active) + dput(active); + return new; + } else { + if (!status) + status = -ENOENT; + } + } + /* + * If we had a mount failure, return status to user space. + * If the mount succeeded and we used a dentry from the active queue + * return it. + */ + if (status) { + dentry = ERR_PTR(status); if (active) dput(active); - return dentry; + } else { + /* + * Valid successful mount, return active dentry or NULL + * for a new dentry. + */ + if (active) + return active; } - if (active) - return active; - return NULL; } @@ -668,8 +834,6 @@ static int autofs4_dir_symlink(struct inode *dir, if (!ino) return -ENOMEM; - autofs4_del_active(dentry); - ino->size = strlen(symname); cp = kmalloc(ino->size + 1, GFP_KERNEL); if (!cp) { @@ -746,7 +910,6 @@ static int autofs4_dir_unlink(struct inode *dir, struct dentry *dentry) dir->i_mtime = CURRENT_TIME; spin_lock(&dcache_lock); - autofs4_add_expiring(dentry); spin_lock(&dentry->d_lock); __d_drop(dentry); spin_unlock(&dentry->d_lock); @@ -772,7 +935,6 @@ static int autofs4_dir_rmdir(struct inode *dir, struct dentry *dentry) spin_unlock(&dcache_lock); return -ENOTEMPTY; } - autofs4_add_expiring(dentry); spin_lock(&dentry->d_lock); __d_drop(dentry); spin_unlock(&dentry->d_lock); @@ -810,8 +972,6 @@ static int autofs4_dir_mkdir(struct inode *dir, struct dentry *dentry, int mode) if (!ino) return -ENOMEM; - autofs4_del_active(dentry); - inode = autofs4_get_inode(dir->i_sb, ino); if (!inode) { if (!dentry->d_fsdata) -- cgit v1.2.2