page_cache_readahead

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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