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Test Your Knowledge in Computers #767
Difficulty: Medium
A victim cache is a cache used to hold blocks evicted from a CPU cache upon replacement.
True or False?
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journal_start(9) [centos man page]

JOURNAL_START(9)					     The Linux Journalling API						  JOURNAL_START(9)

NAME
journal_start - Obtain a new handle. SYNOPSIS
handle_t * journal_start(journal_t * journal, int nblocks); ARGUMENTS
journal Journal to start transaction on. nblocks number of block buffer we might modify DESCRIPTION
We make sure that the transaction can guarantee at least nblocks of modified buffers in the log. We block until the log can guarantee that much space. This function is visible to journal users (like ext3fs), so is not called with the journal already locked. Return a pointer to a newly allocated handle, or an ERR_PTR value on failure. AUTHORS
Roger Gammans <rgammans@computer-surgery.co.uk> Author. Stephen Tweedie <sct@redhat.com> Author. COPYRIGHT
Kernel Hackers Manual 3.10 June 2014 JOURNAL_START(9)

Check Out this Related Man Page

JOURNAL_TRY_TO_FREE_(9) 				     The Linux Journalling API					   JOURNAL_TRY_TO_FREE_(9)

NAME
journal_try_to_free_buffers - try to free page buffers. SYNOPSIS
int journal_try_to_free_buffers(journal_t * journal, struct page * page, gfp_t gfp_mask); ARGUMENTS
journal journal for operation page to try and free gfp_mask we use the mask to detect how hard should we try to release buffers. If __GFP_WAIT and __GFP_FS is set, we wait for commit code to release the buffers. DESCRIPTION
For all the buffers on this page, if they are fully written out ordered data, move them onto BUF_CLEAN so try_to_free_buffers can reap them. This function returns non-zero if we wish try_to_free_buffers to be called. We do this if the page is releasable by try_to_free_buffers. We also do it if the page has locked or dirty buffers and the caller wants us to perform sync or async writeout. 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. This may *change* the value of transaction_t->t_datalist, so anyone who looks at t_datalist needs to lock against this function. Even worse, someone may be doing a journal_dirty_data on this buffer. So we need to lock against that. journal_dirty_data will come out of the lock with the buffer dirty, which makes it ineligible for release here. Who else is affected by this? hmm... Really the only contender is do_get_write_access - it could be looking at the buffer while journal_try_to_free_buffer 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? Return 0 on failure, 1 on success AUTHORS
Roger Gammans <rgammans@computer-surgery.co.uk> Author. Stephen Tweedie <sct@redhat.com> Author. COPYRIGHT
Kernel Hackers Manual 3.10 June 2014 JOURNAL_TRY_TO_FREE_(9)

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