page_cache_readahead
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Name

page_cache_readahead — generic adaptive readahead

Synopsis

unsigned long page_cache_readahead (struct address_space *  mapping,
 struct file_ra_state *  ra,
 struct file *  filp,
 pgoff_t  offset,
 unsigned long  req_size);

Arguments

mapping

address_space which holds the pagecache and I/O vectors

ra

file_ra_state which holds the readahead state

filp

passed on to ->readpage and ->readpages

offset

start offset into mapping, in PAGE_CACHE_SIZE units

req_size

hint: total size of the read which the caller is performing in PAGE_CACHE_SIZE units

Description

page_cache_readahead is the main function. If performs the adaptive readahead window size management and submits the readahead I/O.

Note that filp is purely used for passing on to the ->readpage[s]()

handler

it may refer to a different file from mapping (so we may not use filp->f_mapping or filp->f_dentry->d_inode here). Also, ra may not be equal to &filp->f_ra.

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