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coda: remove CODA_STORE/CODA_RELEASE upcalls
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This is an variation on the patch sent by Christoph Hellwig which kills
file_count abuse by the Coda kernel module by moving the coda_flush
functionality into coda_release.  However part of reason we were using the
coda_flush callback was to allow Coda to pass errors that occur during
writeback from the userspace cache manager back to close().

As Al Viro explained on linux-fsdevel, it is impossible to guarantee that
such errors can in fact be returned back to the caller.  There are many
cases where the last reference to a file is not released by the close
system call and it is also impossible to pick some close as a 'last-close'
and delay it until all other references have been destroyed.

The CODA_STORE/CODA_RELEASE upcall combination is clearly a broken design,
and it is better to remove it completely.

Signed-off-by: Jan Harkes <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Al Viro <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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@jaharkes
jaharkes authored and Linus Torvalds committed Jul 22, 2007
1 parent b507317 commit d3fec42
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Showing 5 changed files with 7 additions and 112 deletions.
1 change: 0 additions & 1 deletion fs/coda/dir.c
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Original file line number Diff line number Diff line change
Expand Up @@ -86,7 +86,6 @@ const struct file_operations coda_dir_operations = {
.read = generic_read_dir,
.readdir = coda_readdir,
.open = coda_open,
.flush = coda_flush,
.release = coda_release,
.fsync = coda_fsync,
};
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65 changes: 6 additions & 59 deletions fs/coda/file.c
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Original file line number Diff line number Diff line change
Expand Up @@ -25,10 +25,6 @@

#include "coda_int.h"

/* if CODA_STORE fails with EOPNOTSUPP, venus clearly doesn't support
* CODA_STORE/CODA_RELEASE and we fall back on using the CODA_CLOSE upcall */
static int use_coda_close;

static ssize_t
coda_file_read(struct file *coda_file, char __user *buf, size_t count, loff_t *ppos)
{
Expand Down Expand Up @@ -163,47 +159,6 @@ int coda_open(struct inode *coda_inode, struct file *coda_file)
return 0;
}

int coda_flush(struct file *coda_file, fl_owner_t id)
{
unsigned short flags = coda_file->f_flags & ~O_EXCL;
unsigned short coda_flags = coda_flags_to_cflags(flags);
struct coda_file_info *cfi;
struct inode *coda_inode;
int err = 0, fcnt;

lock_kernel();

/* last close semantics */
fcnt = file_count(coda_file);
if (fcnt > 1)
goto out;

/* No need to make an upcall when we have not made any modifications
* to the file */
if ((coda_file->f_flags & O_ACCMODE) == O_RDONLY)
goto out;

if (use_coda_close)
goto out;

cfi = CODA_FTOC(coda_file);
BUG_ON(!cfi || cfi->cfi_magic != CODA_MAGIC);

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

err = venus_store(coda_inode->i_sb, coda_i2f(coda_inode), coda_flags,
coda_file->f_uid);

if (err == -EOPNOTSUPP) {
use_coda_close = 1;
err = 0;
}

out:
unlock_kernel();
return err;
}

int coda_release(struct inode *coda_inode, struct file *coda_file)
{
unsigned short flags = (coda_file->f_flags) & (~O_EXCL);
Expand All @@ -215,21 +170,11 @@ int coda_release(struct inode *coda_inode, struct file *coda_file)

lock_kernel();

if (!use_coda_close) {
err = venus_release(coda_inode->i_sb, coda_i2f(coda_inode),
coda_flags);
if (err == -EOPNOTSUPP) {
use_coda_close = 1;
err = 0;
}
}

cfi = CODA_FTOC(coda_file);
BUG_ON(!cfi || cfi->cfi_magic != CODA_MAGIC);

if (use_coda_close)
err = venus_close(coda_inode->i_sb, coda_i2f(coda_inode),
coda_flags, coda_file->f_uid);
err = venus_close(coda_inode->i_sb, coda_i2f(coda_inode),
coda_flags, coda_file->f_uid);

host_inode = cfi->cfi_container->f_path.dentry->d_inode;
cii = ITOC(coda_inode);
Expand All @@ -246,7 +191,10 @@ int coda_release(struct inode *coda_inode, struct file *coda_file)
coda_file->private_data = NULL;

unlock_kernel();
return err;

/* VFS fput ignores the return value from file_operations->release, so
* there is no use returning an error here */
return 0;
}

int coda_fsync(struct file *coda_file, struct dentry *coda_dentry, int datasync)
Expand Down Expand Up @@ -288,7 +236,6 @@ const struct file_operations coda_file_operations = {
.write = coda_file_write,
.mmap = coda_file_mmap,
.open = coda_open,
.flush = coda_flush,
.release = coda_release,
.fsync = coda_fsync,
.splice_read = coda_file_splice_read,
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49 changes: 1 addition & 48 deletions fs/coda/upcall.c
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Original file line number Diff line number Diff line change
Expand Up @@ -160,55 +160,8 @@ int venus_lookup(struct super_block *sb, struct CodaFid *fid,
return error;
}

int venus_store(struct super_block *sb, struct CodaFid *fid, int flags,
vuid_t uid)
{
union inputArgs *inp;
union outputArgs *outp;
int insize, outsize, error;
#ifdef CONFIG_CODA_FS_OLD_API
struct coda_cred cred = { 0, };
cred.cr_fsuid = uid;
#endif

insize = SIZE(store);
UPARG(CODA_STORE);

#ifdef CONFIG_CODA_FS_OLD_API
memcpy(&(inp->ih.cred), &cred, sizeof(cred));
#else
inp->ih.uid = uid;
#endif

inp->coda_store.VFid = *fid;
inp->coda_store.flags = flags;

error = coda_upcall(coda_vcp(sb), insize, &outsize, inp);

CODA_FREE(inp, insize);
return error;
}

int venus_release(struct super_block *sb, struct CodaFid *fid, int flags)
{
union inputArgs *inp;
union outputArgs *outp;
int insize, outsize, error;

insize = SIZE(release);
UPARG(CODA_RELEASE);

inp->coda_release.VFid = *fid;
inp->coda_release.flags = flags;

error = coda_upcall(coda_vcp(sb), insize, &outsize, inp);

CODA_FREE(inp, insize);
return error;
}

int venus_close(struct super_block *sb, struct CodaFid *fid, int flags,
vuid_t uid)
vuid_t uid)
{
union inputArgs *inp;
union outputArgs *outp;
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1 change: 0 additions & 1 deletion include/linux/coda_linux.h
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Original file line number Diff line number Diff line change
Expand Up @@ -36,7 +36,6 @@ extern const struct file_operations coda_ioctl_operations;

/* operations shared over more than one file */
int coda_open(struct inode *i, struct file *f);
int coda_flush(struct file *f, fl_owner_t id);
int coda_release(struct inode *i, struct file *f);
int coda_permission(struct inode *inode, int mask, struct nameidata *nd);
int coda_revalidate_inode(struct dentry *);
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3 changes: 0 additions & 3 deletions include/linux/coda_psdev.h
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Original file line number Diff line number Diff line change
Expand Up @@ -33,9 +33,6 @@ int venus_setattr(struct super_block *, struct CodaFid *, struct coda_vattr *);
int venus_lookup(struct super_block *sb, struct CodaFid *fid,
const char *name, int length, int *type,
struct CodaFid *resfid);
int venus_store(struct super_block *sb, struct CodaFid *fid, int flags,
vuid_t uid);
int venus_release(struct super_block *sb, struct CodaFid *fid, int flags);
int venus_close(struct super_block *sb, struct CodaFid *fid, int flags,
vuid_t uid);
int venus_open(struct super_block *sb, struct CodaFid *fid, int flags,
Expand Down

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