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.TH "EXT2_FIND_SHARED" "" "06 October 2005" "" ""

.SH NAME
ext2_find_shared \- find the indirect blocks for partial truncation.
.SH SYNOPSIS
"SYNOPSIS"
.sp
\fB
.sp
Indirect * ext2_find_shared  (struct inode * \fIinode\fB, int \fIdepth\fB, int * \fIoffsets\fB, Indirect * \fIchain\fB, u32 * \fItop\fB);
\fR
.SH "ARGUMENTS"
.TP
\fB\fIinode\fB\fR
inode in question
.TP
\fB\fIdepth\fB\fR
depth of the affected branch
.TP
\fB\fIoffsets\fB\fR
offsets of pointers in that branch (see ext2_block_to_path)
.TP
\fB\fIchain\fB\fR
place to store the pointers to partial indirect blocks
.TP
\fB\fItop\fB\fR
place to the (detached) top of branch
.SH "DESCRIPTION"
.PP
This is a helper function used by \fBext2_truncate\fR\&.
.PP
When we do \fBtruncate\fR we may have to clean the ends of several indirect
blocks but leave the blocks themselves alive. Block is partially
truncated if some data below the new i_size is refered from it (and
it is on the path to the first completely truncated data block, indeed).
We have to free the top of that path along with everything to the right
of the path. Since no allocation past the truncation point is possible
until \fBext2_truncate\fR finishes, we may safely do the latter, but top
of branch may require special attention - pageout below the truncation
point might try to populate it.
.PP
We atomically detach the top of branch from the tree, store the block
number of its root in *\fItop\fR, pointers to buffer_heads of partially
truncated blocks - in \fIchain\fR[].bh and pointers to their last elements
that should not be removed - in \fIchain\fR[].p. Return value is the pointer
to last filled element of \fIchain\fR\&.
.SH "THE WORK LEFT TO CALLER TO DO THE ACTUAL FREEING OF SUBTREES"
.PP
a) free the subtree starting from *\fItop\fR
b) free the subtrees whose roots are stored in
(\fIchain\fR[i].p+1 .. end of \fIchain\fR[i].bh->b_data)
c) free the subtrees growing from the inode past the \fIchain\fR[0].p
(no partially truncated stuff there).