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kernel
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git-svn-id: https://svn.code.sf.net/p/freedos/svn/kernel/trunk@71 6ac86273-5f31-0410-b378-82cca8765d1b
This commit is contained in:
Jim Tabor 2000-09-05 00:56:50 +00:00
parent 21693a0432
commit d53d9f4445
2 changed files with 70 additions and 7 deletions
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9
docs/history.txt
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@ -1,3 +1,12 @@
2000 Aug 15 - Build 2022
-------- James Tabor (jimtabor@infohwy.com)
2000/08/12 22:49:00 Ron Cemer (roncemer@gte.net)
Fixed writeblock() to only use getbuf() if writing a
complete sector; otherwise use getbloc() and do a
read-modify-write to prevent writing garbage back
over pre-existing data in the file.
This was a major BUG.
2000 Aug 05 - Build 2021
-------- James Tabor (jimtabor@infohwy.com)
Clean up and finish umb code to get 2021 out.

68
kernel/fatfs.c
View File

@ -36,6 +36,17 @@ BYTE *RcsId = "$Id$";
/*
* $Log$
* Revision 1.7 2000/09/05 00:56:50 jimtabor
* *** empty log message ***
*
*
* /// 2000/08/12 22:49:00 Ron Cemer
* Fixed writeblock() to only use getbuf() if writing a
* complete sector; otherwise use getbloc() and do a
* read-modify-write to prevent writing garbage back
* over pre-existing data in the file.
* This was a major BUG.
*
* Revision 1.6 2000/08/06 05:50:17 jimtabor
* Add new files and update cvs with patches and changes
*
@ -1602,6 +1613,15 @@ UCOUNT writeblock(COUNT fd, VOID FAR * buffer, UCOUNT count, COUNT * err)
return 0;
}
/* /// BUG!!! Moved from below next block because we should NOT be able
to truncate the file if we can't write to it. - Ron Cemer */
/* test that we have a valid mode for this fnode */
if (fnp->f_mode != WRONLY && fnp->f_mode != RDWR)
{
*err = DE_INVLDACC;
return 0;
}
/* Test that we are really about to do a data transfer. If the */
/* count is zero and the mode is XFR_READ, just exit. (Any */
/* read with a count of zero is a nop). */
@ -1618,12 +1638,16 @@ UCOUNT writeblock(COUNT fd, VOID FAR * buffer, UCOUNT count, COUNT * err)
return 0;
}
/* /// BUG!!! Moved to above previous block because we should NOT be able
to truncate the file if we can't write to it. - Ron Cemer
/* test that we have a valid mode for this fnode */
/*
if (fnp->f_mode != WRONLY && fnp->f_mode != RDWR)
{
*err = DE_INVLDACC;
return 0;
}
*/
/* The variable secsize will be used later. */
secsize = fnp->f_dpb->dpb_secsize;
@ -1726,14 +1750,40 @@ UCOUNT writeblock(COUNT fd, VOID FAR * buffer, UCOUNT count, COUNT * err)
fnp->f_cluster);
#endif
/* /// Moved xfr_cnt calculation from below so we can
use it to help decide how to get the block:
read-modify-write using getblock() if we are only
going to write part of the block, or
write using getbuf() if we are going to write
the entire block.
- Ron Cemer */
xfr_cnt = min(to_xfer, secsize - fnp->f_boff);
/* get a buffer to store the block in */
if (!getbuf(&bp, (ULONG) clus2phys(fnp->f_cluster,
(fnp->f_dpb->dpb_clsmask + 1),
fnp->f_dpb->dpb_data) + fnp->f_sector,
fnp->f_dpb->dpb_unit))
{
*err = DE_BLKINVLD;
return ret_cnt;
/* /// BUG!!! Added conditional to only use getbuf() if we're going
to write the entire block, which is faster because it does
not first read the block from disk. However, if we are
going to only write part of the block, we MUST use the
getblock() call, which first reads the block from disk.
Without this modification, the kernel was writing garbage
to the file when sequential writes were attempted at less
than the block size. This was causing problems with
piping and redirection in FreeCOM, as well as many other
potential problems.
- Ron Cemer */
if ( (fnp->f_boff == 0) && (xfr_cnt == secsize) ) {
if (!getbuf(&bp, (ULONG) clus2phys(fnp->f_cluster,
(fnp->f_dpb->dpb_clsmask + 1),
fnp->f_dpb->dpb_data) + fnp->f_sector,
fnp->f_dpb->dpb_unit)) {
*err = DE_BLKINVLD;
return ret_cnt;
}
} else {
bp = getblock((ULONG) clus2phys(fnp->f_cluster,
(fnp->f_dpb->dpb_clsmask + 1),
fnp->f_dpb->dpb_data) + fnp->f_sector,
fnp->f_dpb->dpb_unit);
}
/* transfer a block */
@ -1741,7 +1791,11 @@ UCOUNT writeblock(COUNT fd, VOID FAR * buffer, UCOUNT count, COUNT * err)
/* requested transfer size, whichever is smaller. */
/* Then compare to what is left, since we can transfer */
/* a maximum of what is left. */
/* /// Moved xfr_cnt calculation to above getbuf/getblock calls so we can
use it to help decide which one to call.
- Ron Cemer
xfr_cnt = min(to_xfer, secsize - fnp->f_boff);
*/
fbcopy(buffer, (BYTE FAR *) & bp->b_buffer[fnp->f_boff], xfr_cnt);
bp->b_flag |= BFR_DIRTY | BFR_VALID;