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Commit b5ce1d83 authored by Yoshihisa Abe's avatar Yoshihisa Abe Committed by Linus Torvalds
Browse files

Coda: add spin lock to protect accesses to struct coda_inode_info. 



We mostly need it to protect cached user permissions. The c_flags field
is advisory, reading the wrong value is harmless and in the worst case
we hit a slow path where we have to make an extra upcall to the
userspace cache manager when revalidating a dentry or inode.

Signed-off-by: default avatarYoshihisa Abe <yoshiabe@cs.cmu.edu>
Signed-off-by: default avatarJan Harkes <jaharkes@cs.cmu.edu>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3a99c631

fs/coda/cache.c

+12 −5
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#include <linux/string.h>

#include <linux/list.h>

#include <linux/sched.h>

#include <linux/spinlock.h>



#include <linux/coda.h>

#include <linux/coda_linux.h>
@@ -31,19 +32,23 @@ void coda_cache_enter(struct inode *inode, int mask) 
{

	struct coda_inode_info *cii = ITOC(inode);



	spin_lock(&cii->c_lock);

	cii->c_cached_epoch = atomic_read(&permission_epoch);

	if (cii->c_uid != current_fsuid()) {

		cii->c_uid = current_fsuid();

                cii->c_cached_perm = mask;

        } else

                cii->c_cached_perm |= mask;

	spin_unlock(&cii->c_lock);

}



/* remove cached acl from an inode */

void coda_cache_clear_inode(struct inode *inode)

{

	struct coda_inode_info *cii = ITOC(inode);

	spin_lock(&cii->c_lock);

	cii->c_cached_epoch = atomic_read(&permission_epoch) - 1;

	spin_unlock(&cii->c_lock);

}



/* remove all acl caches */
@@ -59,9 +64,11 @@ int coda_cache_check(struct inode *inode, int mask) 
	struct coda_inode_info *cii = ITOC(inode);

	int hit;

	

	spin_lock(&cii->c_lock);

	hit = (mask & cii->c_cached_perm) == mask &&

	    cii->c_uid == current_fsuid() &&

	    cii->c_cached_epoch == atomic_read(&permission_epoch);

	spin_unlock(&cii->c_lock);



	return hit;

}

fs/coda/cnode.c

+14 −5
Original line number Diff line number Diff line
@@ -45,13 +45,15 @@ static void coda_fill_inode(struct inode *inode, struct coda_vattr *attr) 
static int coda_test_inode(struct inode *inode, void *data)

{

	struct CodaFid *fid = (struct CodaFid *)data;

	return coda_fideq(&(ITOC(inode)->c_fid), fid);

	struct coda_inode_info *cii = ITOC(inode);

	return coda_fideq(&cii->c_fid, fid);

}



static int coda_set_inode(struct inode *inode, void *data)

{

	struct CodaFid *fid = (struct CodaFid *)data;

	ITOC(inode)->c_fid = *fid;

	struct coda_inode_info *cii = ITOC(inode);

	cii->c_fid = *fid;

	return 0;

}
@@ -71,6 +73,7 @@ struct inode * coda_iget(struct super_block * sb, struct CodaFid * fid, 
		cii = ITOC(inode);

		/* we still need to set i_ino for things like stat(2) */

		inode->i_ino = hash;

		/* inode is locked and unique, no need to grab cii->c_lock */

		cii->c_mapcount = 0;

		unlock_new_inode(inode);

	}
@@ -107,14 +110,20 @@ int coda_cnode_make(struct inode **inode, struct CodaFid *fid, struct super_bloc 
}





/* Although we treat Coda file identifiers as immutable, there is one

 * special case for files created during a disconnection where they may

 * not be globally unique. When an identifier collision is detected we

 * first try to flush the cached inode from the kernel and finally

 * resort to renaming/rehashing in-place. Userspace remembers both old

 * and new values of the identifier to handle any in-flight upcalls.

 * The real solution is to use globally unique UUIDs as identifiers, but

 * retrofitting the existing userspace code for this is non-trivial. */

void coda_replace_fid(struct inode *inode, struct CodaFid *oldfid, 

		      struct CodaFid *newfid)

{

	struct coda_inode_info *cii;

	struct coda_inode_info *cii = ITOC(inode);

	unsigned long hash = coda_f2i(newfid);

	

	cii = ITOC(inode);



	BUG_ON(!coda_fideq(&cii->c_fid, oldfid));



	/* replace fid and rehash inode */

fs/coda/dir.c

+6 −0
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 
#include <linux/errno.h>

#include <linux/string.h>

#include <linux/smp_lock.h>

#include <linux/spinlock.h>



#include <asm/uaccess.h>
@@ -617,7 +618,9 @@ static int coda_dentry_revalidate(struct dentry *de, struct nameidata *nd) 
		goto out;



	/* clear the flags. */

	spin_lock(&cii->c_lock);

	cii->c_flags &= ~(C_VATTR | C_PURGE | C_FLUSH);

	spin_unlock(&cii->c_lock);



bad:

	unlock_kernel();
@@ -691,7 +694,10 @@ int coda_revalidate_inode(struct dentry *dentry) 
			goto return_bad;

		

		coda_flag_inode_children(inode, C_FLUSH);



		spin_lock(&cii->c_lock);

		cii->c_flags &= ~(C_VATTR | C_PURGE | C_FLUSH);

		spin_unlock(&cii->c_lock);

	}



ok:

fs/coda/file.c

+10 −2
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#include <linux/cred.h>

#include <linux/errno.h>

#include <linux/smp_lock.h>

#include <linux/spinlock.h>

#include <linux/string.h>

#include <linux/slab.h>

#include <asm/uaccess.h>
@@ -109,19 +110,24 @@ coda_file_mmap(struct file *coda_file, struct vm_area_struct *vma) 


	coda_inode = coda_file->f_path.dentry->d_inode;

	host_inode = host_file->f_path.dentry->d_inode;



	cii = ITOC(coda_inode);

	spin_lock(&cii->c_lock);

	coda_file->f_mapping = host_file->f_mapping;

	if (coda_inode->i_mapping == &coda_inode->i_data)

		coda_inode->i_mapping = host_inode->i_mapping;



	/* only allow additional mmaps as long as userspace isn't changing

	 * the container file on us! */

	else if (coda_inode->i_mapping != host_inode->i_mapping)

	else if (coda_inode->i_mapping != host_inode->i_mapping) {

		spin_unlock(&cii->c_lock);

		return -EBUSY;

	}



	/* keep track of how often the coda_inode/host_file has been mmapped */

	cii = ITOC(coda_inode);

	cii->c_mapcount++;

	cfi->cfi_mapcount++;

	spin_unlock(&cii->c_lock);



	return host_file->f_op->mmap(host_file, vma);

}
@@ -185,11 +191,13 @@ int coda_release(struct inode *coda_inode, struct file *coda_file) 
	cii = ITOC(coda_inode);



	/* did we mmap this file? */

	spin_lock(&cii->c_lock);

	if (coda_inode->i_mapping == &host_inode->i_data) {

		cii->c_mapcount -= cfi->cfi_mapcount;

		if (!cii->c_mapcount)

			coda_inode->i_mapping = &coda_inode->i_data;

	}

	spin_unlock(&cii->c_lock);



	fput(cfi->cfi_container);

	kfree(coda_file->private_data);

fs/coda/inode.c

+2 −0
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#include <linux/errno.h>

#include <linux/unistd.h>

#include <linux/smp_lock.h>

#include <linux/spinlock.h>

#include <linux/file.h>

#include <linux/vfs.h>

#include <linux/slab.h>
@@ -51,6 +52,7 @@ static struct inode *coda_alloc_inode(struct super_block *sb) 
	ei->c_flags = 0;

	ei->c_uid = 0;

	ei->c_cached_perm = 0;

	spin_lock_init(&ei->c_lock);

	return &ei->vfs_inode;

}