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VFS/PFS: remove notion of position in pipes

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Because pipes have no file position. VFS maintained (file) offsets into a
buffer internal to PFS and stored them in vnodes for simplicity, mixing
the responsibilities of filp and vnode objects.

With this patch PFS ignores the position field in REQ_READ and REQ_WRITE
requests making VFS' job a lot simpler.
This commit is contained in:
Thomas Veerman 2012-12-11 19:46:09 +00:00
parent 7c8b3ddfed
commit 3de8d1cf6e
7 changed files with 51 additions and 57 deletions
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29
servers/pfs/read.c
View file

@ -32,23 +32,34 @@ int fs_readwrite(message *fs_m_in, message *fs_m_out)
/* Get the values from the request message */
rw_flag = (fs_m_in->m_type == REQ_READ ? READING : WRITING);
gid = (cp_grant_id_t) fs_m_in->REQ_GRANT;
position = fs_m_in->REQ_SEEK_POS_LO;
nrbytes = (unsigned) fs_m_in->REQ_NBYTES;
/* We can't read beyond the max file position */
if (nrbytes > MAX_FILE_POS) return(EFBIG);
if (rw_flag == WRITING) {
/* Check in advance to see if file will grow too big. */
/* Casting nrbytes to signed is safe, because it's guaranteed not to
be beyond max signed value (i.e., MAX_FILE_POS). */
if (position > PIPE_BUF - (signed) nrbytes) return(EFBIG);
}
/* Mark inode in use */
if ((get_inode(rip->i_dev, rip->i_num)) == NULL) return(err_code);
if ((bp = get_block(rip->i_dev, rip->i_num)) == NULL) return(err_code);
if (rw_flag == WRITING) {
/* Check in advance to see if file will grow too big. */
/* Casting nrbytes to signed is safe, because it's guaranteed not to
* be beyond max signed value (i.e., MAX_FILE_POS).
*/
position = rip->i_size;
if (position > PIPE_BUF - (signed) nrbytes) {
put_inode(rip);
put_block(rip->i_dev, rip->i_num);
return(EFBIG);
}
} else {
position = bp->b_bytes;
if (nrbytes > rip->i_size - position) {
/* There aren't that many bytes to read */
nrbytes = rip->i_size - position;
}
}
if (rw_flag == READING) {
/* Copy a chunk from the block buffer to user space. */
r = sys_safecopyto(VFS_PROC_NR, gid, (vir_bytes) 0,
@ -78,10 +89,12 @@ int fs_readwrite(message *fs_m_in, message *fs_m_out)
}
}
if (rw_flag == READING)
bp->b_bytes = position;
if (rw_flag == READING) rip->i_update |= ATIME;
if (rw_flag == WRITING) rip->i_update |= CTIME | MTIME;
fs_m_out->RES_NBYTES = (size_t) cum_io;
put_inode(rip);
put_block(rip->i_dev, rip->i_num);

2
servers/vfs/open.c
View file

@ -248,8 +248,6 @@ int common_open(char path[PATH_MAX], int oflags, mode_t omode)
r = map_vnode(vp, PFS_PROC_NR);
if (r == OK) {
if (vp->v_ref_count == 1) {
vp->v_pipe_rd_pos = 0;
vp->v_pipe_wr_pos = 0;
if (vp->v_size != 0)
r = truncate_vnode(vp, 0);
}

26
servers/vfs/pipe.c
View file

@ -108,8 +108,6 @@ int do_pipe()
vp->v_inode_nr = res.inode_nr;
vp->v_mapinode_nr = res.inode_nr;
vp->v_mode = res.fmode;
vp->v_pipe_rd_pos= 0;
vp->v_pipe_wr_pos= 0;
vp->v_fs_count = 1;
vp->v_mapfs_count = 1;
vp->v_ref_count = 1;
@ -175,13 +173,13 @@ endpoint_t map_to_fs_e;
/*===========================================================================*
* pipe_check *
*===========================================================================*/
int pipe_check(vp, rw_flag, oflags, bytes, position, notouch)
register struct vnode *vp; /* the inode of the pipe */
int rw_flag; /* READING or WRITING */
int oflags; /* flags set by open or fcntl */
register int bytes; /* bytes to be read or written (all chunks) */
u64_t position; /* current file position */
int notouch; /* check only */
int pipe_check(
struct vnode *vp, /* the inode of the pipe */
int rw_flag, /* READING or WRITING */
int oflags, /* flags set by open or fcntl */
int bytes, /* bytes to be read or written (all chunks) */
int notouch /* check only */
)
{
/* Pipes are a little different. If a process reads from an empty pipe for
* which a writer still exists, suspend the reader. If the pipe is empty
@ -191,13 +189,15 @@ int notouch; /* check only */
off_t pos;
int r = OK;
if (ex64hi(position) != 0)
panic("pipe_check: position too large in pipe");
pos = ex64lo(position);
/* Reads start at the beginning; writes append to pipes */
if (rw_flag == READING)
pos = 0;
else
pos = vp->v_size;
/* If reading, check for empty pipe. */
if (rw_flag == READING) {
if (pos >= vp->v_size) {
if (vp->v_size == 0) {
/* Process is reading from an empty pipe. */
if (find_filp(vp, W_BIT) != NULL) {
/* Writer exists */

2
servers/vfs/proto.h
View file

@ -187,7 +187,7 @@ int do_pipe(void);
int map_vnode(struct vnode *vp, endpoint_t fs_e);
void unpause(endpoint_t proc_e);
int pipe_check(struct vnode *vp, int rw_flag, int oflags, int bytes,
u64_t position, int notouch);
int notouch);
void release(struct vnode *vp, int op, int count);
void revive(endpoint_t proc_e, int returned);
void suspend(int why);

37
servers/vfs/read.c
View file

@ -272,12 +272,12 @@ size_t req_size;
oflags = f->filp_flags;
vp = f->filp_vno;
position = cvu64((rw_flag == READING) ? vp->v_pipe_rd_pos :
vp->v_pipe_wr_pos);
position = cvu64(0); /* Not actually used */
/* fp->fp_cum_io_partial is only nonzero when doing partial writes */
cum_io = fp->fp_cum_io_partial;
r = pipe_check(vp, rw_flag, oflags, req_size, position, 0);
r = pipe_check(vp, rw_flag, oflags, req_size, 0);
if (r <= 0) {
if (r == SUSPEND) pipe_suspend(f, buf, req_size);
return(r);
@ -287,16 +287,8 @@ size_t req_size;
if (size < req_size) partial_pipe = 1;
/* Truncate read request at size. */
if((rw_flag == READING) &&
cmp64ul(add64ul(position, size), vp->v_size) > 0) {
/* Position always should fit in an off_t (LONG_MAX). */
off_t pos32;
assert(cmp64ul(position, LONG_MAX) <= 0);
pos32 = cv64ul(position);
assert(pos32 >= 0);
assert(pos32 <= LONG_MAX);
size = vp->v_size - pos32;
if (rw_flag == READING && size > vp->v_size) {
size = vp->v_size;
}
if (vp->v_mapfs_e == 0)
@ -309,7 +301,6 @@ size_t req_size;
if (ex64hi(new_pos))
panic("rw_pipe: bad new pos");
position = new_pos;
cum_io += cum_io_incr;
buf += cum_io_incr;
req_size -= cum_io_incr;
@ -317,27 +308,19 @@ size_t req_size;
/* On write, update file size and access time. */
if (rw_flag == WRITING) {
if (cmp64ul(position, vp->v_size) > 0) {
if (ex64hi(position) != 0) {
if (cmp64ul(new_pos, vp->v_size) > 0) {
if (ex64hi(new_pos) != 0) {
panic("read_write: file size too big for v_size");
}
vp->v_size = ex64lo(position);
vp->v_size = ex64lo(new_pos);
}
} else {
if (cmp64ul(position, vp->v_size) >= 0) {
/* Reset pipe pointers */
if (cmp64ul(new_pos, vp->v_size) >= 0) {
/* Pipe emtpy; reset size */
vp->v_size = 0;
vp->v_pipe_rd_pos= 0;
vp->v_pipe_wr_pos= 0;
position = cvu64(0);
}
}
if (rw_flag == READING)
vp->v_pipe_rd_pos= cv64ul(position);
else
vp->v_pipe_wr_pos= cv64ul(position);
if (r == OK) {
if (partial_pipe) {
/* partial write on pipe with */

6
servers/vfs/select.c
View file

@ -451,7 +451,8 @@ static int select_request_pipe(struct filp *f, int *ops, int block)
orig_ops = *ops;
if ((*ops & (SEL_RD|SEL_ERR))) {
err = pipe_check(f->filp_vno, READING, 0, 1, f->filp_pos, 1);
/* Check if we can read 1 byte */
err = pipe_check(f->filp_vno, READING, 0, 1, 1 /* Check only */);
if (err != SUSPEND)
r |= SEL_RD;
@ -466,7 +467,8 @@ static int select_request_pipe(struct filp *f, int *ops, int block)
}
if ((*ops & (SEL_WR|SEL_ERR))) {
err = pipe_check(f->filp_vno, WRITING, 0, 1, f->filp_pos, 1);
/* Check if we can write 1 byte */
err = pipe_check(f->filp_vno, WRITING, 0, 1, 1 /* Check only */);
if (err != SUSPEND)
r |= SEL_WR;

2
servers/vfs/vnode.h
View file

@ -16,8 +16,6 @@ EXTERN struct vnode {
#if 0
int v_ref_check; /* for consistency checks */
#endif
off_t v_pipe_rd_pos;
off_t v_pipe_wr_pos;
endpoint_t v_bfs_e; /* endpoint number for the FS proces in case
of a block special file */
dev_t v_dev; /* device number on which the corresponding