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ecm fix 4 dos extend map fail #248

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ecm fix 4 dos extend map fail #248

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6e6a6b1
fatfs.c: move directory size adjust to dos_extend, if map_cluster failed
ecm-pushbx Apr 23, 2026
d08f0ec
fatfs.c: no alloc cluster too much if CX = 0 and seek on boundary
ecm-pushbx Apr 23, 2026
5aa0aa5
fatfs.c: fix to prior commit if WRITEZEROS defined
ecm-pushbx Apr 23, 2026
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60 changes: 46 additions & 14 deletions kernel/fatfs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1024,17 +1024,6 @@ COUNT map_cluster(REG f_node_ptr fnp, COUNT mode)
cluster = extend(fnp);
if (cluster == LONG_LAST_CLUSTER)
return DE_HNDLDSKFULL;

/* ecm: finally the right solution, only extend/modify
file size after having just appended a cluster. */
fnp->f_dir.dir_size =
(((ULONG)fnp->f_cluster_offset + 2)
/* at 0 we will increment to 1, having allocated the second
cluster, so + 2 for the then-total size. */
* (ULONG)fnp->f_dpb->dpb_secsize)
<<
fnp->f_dpb->dpb_shftcnt;
merge_file_changes(fnp, FALSE);
}

fnp->f_cluster = cluster;
Expand All @@ -1055,7 +1044,7 @@ COUNT map_cluster(REG f_node_ptr fnp, COUNT mode)
/* #define WRITEZEROS 1 */
/* but because we want to be compatible, we don't do this by */
/* default */
STATIC COUNT dos_extend(f_node_ptr fnp)
STATIC COUNT dos_extend(f_node_ptr fnp, BOOL emptywrite)
{
#ifdef WRITEZEROS
struct buffer FAR *bp;
Expand All @@ -1075,8 +1064,39 @@ STATIC COUNT dos_extend(f_node_ptr fnp)
while (count > 0)
#endif
{
if (map_cluster(fnp, XFR_WRITE) != SUCCESS)
BOOL special = 0;
if (emptywrite
#ifdef WRITEZEROS
&& fnp->f_offset != 0
#else
/* f_offset != 0 always true here */
#endif
&& ((fnp->f_offset &
(((ULONG)fnp->f_dpb->dpb_secsize
<< fnp->f_dpb->dpb_shftcnt) - 1)
)
== 0)
) {
special = 1;
-- fnp->f_offset;
}
if (map_cluster(fnp, XFR_WRITE) != SUCCESS) {
if (special) ++ fnp->f_offset;
if (fnp->f_cluster != FREE) {
/* ecm: write size if couldn't satisfy full request,
but at least one cluster is allocated. */
fnp->f_dir.dir_size =
(((ULONG)fnp->f_cluster_offset + 1)
/* at 0 we have incremented to 1, having allocated the second
cluster, so + 1 for the then-total size. */
* (ULONG)fnp->f_dpb->dpb_secsize)
<<
fnp->f_dpb->dpb_shftcnt;
merge_file_changes(fnp, FALSE);
}
return DE_HNDLDSKFULL;
}
if (special) ++ fnp->f_offset;

#ifdef WRITEZEROS
/* Compute the block within the cluster and the offset */
Expand Down Expand Up @@ -1106,6 +1126,18 @@ STATIC COUNT dos_extend(f_node_ptr fnp)
}
if (bp == NULL)
{
if (fnp->f_cluster != FREE) {
/* ecm: write size if couldn't satisfy full request,
but at least one cluster is allocated. */
fnp->f_dir.dir_size =
(((ULONG)fnp->f_cluster_offset + 1)
/* at 0 we have incremented to 1, having allocated the second
cluster, so + 1 for the then-total size. */
* (ULONG)fnp->f_dpb->dpb_secsize)
<<
fnp->f_dpb->dpb_shftcnt;
merge_file_changes(fnp, FALSE);
}
return DE_ACCESS;
}

Expand Down Expand Up @@ -1221,7 +1253,7 @@ long rwblock(COUNT fd, VOID FAR * buffer, UCOUNT count, int mode)
/* mark file as modified and set date not valid any more */
fnp->f_flags &= ~(SFT_FCLEAN|SFT_FDATE);

if (dos_extend(fnp) != SUCCESS)
if (dos_extend(fnp, count == 0) != SUCCESS)
{
/* ecm: control flow may end up here if CX = 0000h and
the extending failed to allocate a cluster
Expand Down