netfs_start_io_read(9)

✨ netfs_start_io_read — like, the official "hey we're doing a buffered read rn" declaration 💅

okay so bestie, this one lives in section 9 of the Kernel API Manual and honestly? it's giving gatekeeper energy. it's the function you call to be like "hey everybody, a buffered read is about to happen, please don't do anything weird" 🫶

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🎀 SYNOPSIS

int netfs_start_io_read (struct inode *inode );

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🌸 ARGUMENTS

• inode — the file inode. that's it. that's the whole parameter. it's the file we're about to read from, bestie 💖

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🦋 DESCRIPTION

okay so here's the vibe: you call this to declare that a buffered read operation is about to start, and the whole point is making sure we block all direct I/O. no cap, that's the job 🔥

when it returns, the function guarantees the NETFS_ICTX_ODIRECT flag is unset, and it's holding a shared lock on inode->i_rwsem so that flag literally cannot be changed while you're holding it. iconic behavior honestly.

in practice, what that means:

• buffered read operations get to run in parallel — thank you shared lock, we love you 💜
• direct I/O operations have to wait to grab an exclusive lock in order to set NETFS_ICTX_ODIRECT 🫠

heads up: buffered writes and truncates both take a write lock on inode->i_rwsem, which means those get serialised with respect to the reads. so like... they're not invited to the parallel party 🎀

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🌈 SEE ALSO

all the sibling functions in the family group chat, plus the kernel file itself:

• Kernel file ./fs/netfs/locking.c
• netfs_end_io_read(9)
• netfs_start_io_write(9)
• netfs_end_io_write(9)
• netfs_start_io_direct(9)
• netfs_end_io_direct(9)
• netfs_wb_begin(9)

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alright bestie, that's the whole page ✨ it comes to you from ./fs/netfs, dated October 2026, and yeah — it's netfs_start_io_read(9) top to bottom, no notes 💅💖