.\" This documentation was generated from the book titled "The Linux Journalling API", which is part of the Linux kernel source. .\" .\" Documentation by: Roger Gammans (rgammans@computer-surgery.co.uk) .\" Documentation by: Stephen Tweedie (sct@redhat.com) .\" Documentation copyright: 2002 Roger Gammans .\" This documentation comes with the following legal notice: .\" .\" This documentation is free software; you can redistribute .\" it and/or modify it under the terms of the GNU General Public .\" License as published by the Free Software Foundation; either .\" version 2 of the License, or (at your option) any later .\" version. .\" .\" This program is distributed in the hope that it will be .\" useful, but WITHOUT ANY WARRANTY; without even the implied .\" warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. .\" See the GNU General Public License for more details. .\" .\" You should have received a copy of the GNU General Public .\" License along with this program; if not, write to the Free .\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, .\" MA 02111-1307 USA .\" .\" For more details see the file COPYING in the source .\" distribution of Linux. .\" .\" For comments on the formatting of this manpage, please contact Michael Still .\" This manpage has been automatically generated by docbook2man .\" from a DocBook document. This tool can be found at: .\" .\" Please send any bug reports, improvements, comments, patches, .\" etc. to Steve Cheng . .TH "JOURNAL_TRY_TO_FREE_BUFFERS" "9" "07 August 2003" "" "" .SH NAME journal_try_to_free_buffers \- try to free page buffers. .SH SYNOPSIS .sp \fB .sp int journal_try_to_free_buffers (journal_t * \fIjournal\fB, struct page * \fIpage\fB, int \fIunused_gfp_mask\fB); \fR .SH "ARGUMENTS" .TP \fB\fIjournal\fB\fR journal for operation .TP \fB\fIpage\fB\fR to try and free .TP \fB\fIunused_gfp_mask\fB\fR -- undescribed -- .SH "DESCRIPTION" .PP .PP For all the buffers on this page, if they are fully written out ordered data, move them onto BUF_CLEAN so \fBtry_to_free_buffers\fR can reap them. .PP This function returns non-zero if we wish \fBtry_to_free_buffers\fR to be called. We do this if the page is releasable by \fBtry_to_free_buffers\fR. We also do it if the page has locked or dirty buffers and the caller wants us to perform sync or async writeout. .PP This complicates JBD locking somewhat. We aren't protected by the BKL here. We wish to remove the buffer from its committing or running transaction's ->t_datalist via __journal_unfile_buffer. .PP This may *change* the value of transaction_t->t_datalist, so anyone who looks at t_datalist needs to lock against this function. .PP Even worse, someone may be doing a journal_dirty_data on this buffer. So we need to lock against that. \fBjournal_dirty_data\fR will come out of the lock with the buffer dirty, which makes it ineligible for release here. .PP Who else is affected by this? hmm... Really the only contender is \fBdo_get_write_access\fR - it could be looking at the buffer while \fBjournal_try_to_free_buffer\fR is changing its state. But that cannot happen because we never reallocate freed data as metadata while the data is part of a transaction. Yes? .SH "ABOUT THIS DOCUMENT" .PP This documentation was generated with kernel version 2.6.0.