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VFS, FSes: add REQ_PEEK request type

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REQ_PEEK behaves just like REQ_READ except that it does not copy
data anywhere, just obtains the blocks from the FS into the cache.

To be used by the future mmap implementation.

Change-Id: I1b56de304f0a7152b69a72c8962d04258adb44f9
This commit is contained in:
Ben Gras
2013-03-07 10:57:38 +00:00
parent 1ba514e19c
commit a9f55a2e46
15 changed files with 116 additions and 37 deletions
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servers/ext2/read.c
+19 -6
View File
@@ -60,8 +60,13 @@ int fs_readwrite(void)
if (f_size < 0) f_size = MAX_FILE_POS;
}
/* Get the values from the request message */
rw_flag = (fs_m_in.m_type == REQ_READ ? READING : WRITING);
switch(fs_m_in.m_type) {
case REQ_READ: rw_flag = READING; break;
case REQ_WRITE: rw_flag = WRITING; break;
case REQ_PEEK: rw_flag = PEEKING; break;
default: panic("odd request");
}
gid = (cp_grant_id_t) fs_m_in.REQ_GRANT;
position = (off_t) fs_m_in.REQ_SEEK_POS_LO;
nrbytes = (size_t) fs_m_in.REQ_NBYTES;
@@ -206,7 +211,7 @@ u64_t position; /* position within file to read or write */
unsigned off; /* off within the current block */
unsigned int chunk; /* number of bytes to read or write */
unsigned left; /* max number of bytes wanted after position */
int rw_flag; /* READING or WRITING */
int rw_flag; /* READING, WRITING or PEEKING */
cp_grant_id_t gid; /* grant */
unsigned buf_off; /* offset in grant */
unsigned int block_size; /* block size of FS operating on */
@@ -214,12 +219,18 @@ int *completed; /* number of bytes copied */
{
/* Read or write (part of) a block. */
register struct buf *bp;
register struct buf *bp = NULL;
register int r = OK;
int n, block_spec;
block_t b;
dev_t dev;
/* rw_flag:
* READING: read from FS, copy to user
* WRITING: copy from user, write to FS
* PEEKING: try to get all the blocks into the cache, no copying
*/
*completed = 0;
block_spec = (rip->i_mode & I_TYPE) == I_BLOCK_SPECIAL;
@@ -244,11 +255,13 @@ int *completed; /* number of bytes copied */
}
return r;
} else {
/* Writing to a nonexistent block. Create and enter in inode.*/
/* Writing to or peeking a nonexistent block.
* Create and enter in inode.
*/
if ((bp = new_block(rip, (off_t) ex64lo(position))) == NULL)
return(err_code);
}
} else if (rw_flag == READING) {
} else if (rw_flag == READING || rw_flag == PEEKING) {
/* Read and read ahead if convenient. */
bp = rahead(rip, b, position, left);
} else {
@@ -275,7 +288,7 @@ int *completed; /* number of bytes copied */
/* Copy a chunk from the block buffer to user space. */
r = sys_safecopyto(VFS_PROC_NR, gid, (vir_bytes) buf_off,
(vir_bytes) (b_data(bp)+off), (size_t) chunk);
} else {
} else if(rw_flag == WRITING) {
/* Copy a chunk from user space to the block buffer. */
r = sys_safecopyfrom(VFS_PROC_NR, gid, (vir_bytes) buf_off,
(vir_bytes) (b_data(bp)+off), (size_t) chunk);
servers/ext2/table.c
+1
View File
@@ -46,4 +46,5 @@ int (*fs_call_vec[])(void) = {
fs_rdlink, /* 30 */
fs_getdents, /* 31 */
fs_statvfs, /* 32 */
fs_readwrite, /* 33 */
};